Farzana Alibay
email: farzana.alibay@gmail.com

Manolya Kavakli
email: manolya.kavakli@mq.edu.au

Jean-Rémy Chardonnet
email: jean-remy.chardonnet@ensam.eu

Muhammad Zeeshan Baig

§ Muhammad

Zeeshan Baig
email: baig.mzeeshan@gmail.com

The Usability of Speech and/or Gestures in Multi-Modal Interface Systems

Keywords: •Human-centered computing → Human computer interaction (HCI), Interaction design, User interface design, Gesture, Speech, Semantics, Emotion Recognition, Kinect, 3D object, Leap Motion

Multi-Modal Interface Systems (MMIS) have proliferated in the last few decades, since they provide a direct interface for both Human Computer Interaction (HCI) and face-to-face communication. Our aim is to provide users without any prior 3D modelling experience, with a multi-modal interface to create a 3D object. The system also incorporates help throughout the drawing process and identifies simple words and gestures to accomplish a range of (simple to complex) modeling tasks. We have developed a multi-modal interface that allows users to design objects in 3D, using AutoCAD commands as well as speech and gesture. We have used a microphone to collect speech input and a Leap Motion sensor to collect gesture input in real time. Two sets of experiments were conducted to investigate the usability of the system and evaluate the system performance using Leap Motion versus keyboard and mouse. Our results indicate that performing a task using speech is perceived exhausting, when there is no shared vocabulary between man and machine, and the usability of traditional input devices supersedes

INTRODUCTION

In the last decades, many efforts have been made to improve the performance of uni-modal and multi-modal interpreters. A Multi-Modal Interface System (MMIS) aggregates two or more user input modes in an interconnected fashion with multimedia output. The user input can be speech, pen, touch, manual gesture, gaze, head, and body movements [START_REF] Oviatt | Advances in robust multimodal interface design[END_REF]. One of the main problems in the field of MMIS is to develop systems that utilize human behavior and language to interact with computers. Speech input has been extensively used in smartphones especially for developing commercial products. Another popular input mode is gestures, inspiring many researchers to develop gesture recognition systems and algorithms for HCI with practical applications [START_REF] Erol | Vision-based hand pose estimation: A review[END_REF]. There is some evidence suggesting that a MMIS not only improves handling and reliability of the system, but also task completion rates compared to unimodal systems [START_REF] Oviatt | Multimodal interactive maps: Designing for human performance[END_REF]. However, the need for a multi-modal interface instead of a single input interface is relatively less explored. In this paper we investigate the usability of speech and hand gestures in a multi-modal versus traditional interface.

A typical MMIS design consists of a recognition system that translates human tasks into recognizable computer signals. Once the human input has been identified, the next step is to interpret the inputs and aggregate them to achieve a desired output. Most examples in the literature use speech and pen input in MMIS design [START_REF] Liu | A survey of speech-hand gesture recognition for the development of multimodal interfaces in computer games[END_REF]. An early example was from Bolt's "Put That There" multimodal system that combined speech and pointing gestures to move an object [START_REF] Bolt | Voice and gesture at the graphics interface[END_REF].

Some recent applications have also utilized gesture input and combined it with speech to draw sketches and compare them with hand-drawn sketches [START_REF] Kavakli | Impacts of culture on gesture based interfaces[END_REF]. Most of these systems have used Kinect and Leap Motion to recognize gesture input. The speech has provided an extra dimension for information required to interact with the computer in cases such as coloring or rotating the object [START_REF] Rodger | A field study of the impact of gender and user's technical experience on the performance of voice-activated medical tracking application[END_REF].

While combining two input sets is beneficial for some applications, it may not be so beneficial or preferable in some others. For example, in a modeling software, many complex words are used to draw a 3D object. The users have to be familiar with the vocabulary and have to learn how to navigate in the 3D space. This research investigates: the effectiveness of using simple words and gestures to design or navigate in the 3D space, the combination of speech and gesture inputs to perform design tasks and facilitate the design process, the easiness for a user to use speech and gesture recognition systems instead of a keyboard and mouse, and the ideal type of communication channel for designer-computer interaction.

The research aims to provide users without any prior 3D modelling experience, with a multi-modal interface to create a 3D object. The system also incorporates help throughout the drawing process and identifies simple words and gestures to accomplish a range of (simple to complex) modeling tasks.

In Section 2, we explain the methodology of the project. Section 3 sheds light on the experimental process. Evaluation of the experimental results is given in Section 4, before conclusion.

RESEARCH METHODOLOGY

To test the usability of multi-modal and uni-modal input systems, we have developed a system to model a 3D object using gesture and speech inputs. In this section, we will describe the system design and architecture. As the design concept, we developed a model to convert speech and gesture actions into commands given in AutoCAD.

System Specifications

We have used an Intel Core i7 desktop PC, with a Microsoft Windows 8.1 operating system. For gesture recognition, we have used a Leap Motion sensor, instead of Kinect, since our pilot experiments showed that Kinect 1.0 does not allow recognition of users' fingers [START_REF] Weichert | Analysis of the accuracy and robustness of the leap motion controller[END_REF]. Therefore, Leap Motion and its API have been chosen for gesture input, since it offers facilities for finger recognition [START_REF] Marin | Hand gesture recognition with leap motion and kinect devices[END_REF]. For speech recognition and synthesis, we have used a typical microphone and the Microsoft Speech Recognition API. We have chosen to use the AutoCAD 2017 3D modeling software for the users to design an object. To create an AutoCAD plugin, ObjectARX 2017 SDK was installed [START_REF]Objectarx developer's guide[END_REF]. For implementation of the system, we used C# with the Microsoft Visual Studio 2015 Environment.

Design Concept

For experimental purposes, we have identified a classical chair example to draw and manipulate using multi-modal input. We have analyzed the necessary processes for this design concept.

Manipulation and Object Identification

The classical manipulation processes to draw an object involve functions such as select, move, rotate, delete, copy, and scale. We have defined possible actions using speech and gesture inputs to apply the above-mentioned manipulation functions. For example, to rotate an object, the user has to first select it. The object can be selected using speech or gesture. To select it using gestures, the user needs to navigate the cursor to it and perform a clicking gesture. To perform the same actions using speech and gestures, first the user needs to navigate the cursor to the object and then say the keyword "select" to select the object. To rotate it with a gesture, the user needs to hang on to the clicking gesture and rotate it with the hand position. If the user wants to perform rotation with speech, the keyword "rotate to" followed by the direction of rotation, which should be 90, 45 or 180 degrees, is used. The same set of AutoCAD commands has been used for all other manipulation actions: first select the object and then use keywords to manipulate it. In summary, to perform a task using both gestures and speech, the process is much more complicated.

Drawing identification and manipulation

To draw a chair, first we need to draw shapes in AutoCAD such as a rectangle, a cylinder, an arc, etc. We also need to have the ability to round the shapes and give some height and thickness to a surface. Finally, we also incorporate the functionality of applying a texture, material and color. For example, if we need to draw a box using speech, first we need to say "I want to draw a box"; the system will look for the word "Draw" in the speech and find the shape, which in this case is a box. After the object has been selected, the next step is to specify the position, which can be defined using the command "the position is x, y, z", where x, y, z are coordinates in 3D. The third step is to give the object a size or dimensions; to achieve this task the user needs to say "the size is x, y", where x and y are the length and the width. We also have to mention the height of the object by saying "the height is z", where z is the height of the specified object. For a circular object, the user needs to mention the radius instead of the size.

If the user wants to perform the same tasks using gestures, all he needs is to use the hands to locate the position and click on the specific icon to draw a shape, using the clicking gesture; then, with the help of the click and hold function, the size and height of the object should be adjusted. To assign a color or material to the object, after selecting the object, a speech command "the material or color is" can be used. In this project, only wooden material and gray color can be assigned to an object.

Usually, in a modeling software, there are two possible ways to manipulate the camera view; either using a mouse or the orbit. The orbit is the easiest way to move the camera by clicking directly on the cube (top, right, left, back, down, front or the corner right/back or right/front). With speech, we can move the camera using classical directions such as 'move camera vertically and horizontally' and 'zoom in and out'. We also orientate the camera by specifying the number of degrees and the direction, stating "orientate the camera to 45 degrees on the right". Using speech, if no number is specified with the direction, then the default value is applied (1 degree, or 1 cm). Using gestures, the camera can be activated or deactivated: when the system detects a closed hand followed by an open hand, it activates or deactivates the camera.

Table 1 shows a detailed description of the words used in speech and the corresponding AutoCAD commands. For gestures, the user needs to utilize the clicking gesture on the icon or a tool to enable that command.

During the experiment, we have implemented a user-assistance system, so that the user enables the assistance by saying "Help me, please". This instantiates the help sequence and offers a way to perform an action. The system also provides assistance, while performing an action. For example, if the user chooses to draw a box, the system will ask him to choose the position. Once the user chooses the position either by speech or gesture, the system asks him to choose the size and height. The system anticipates the next step for the current action and guides the user to perform it.

IMPLEMENTATION

To implement the design concept, we have created a dll plugin for AutoCAD containing 4 main classes: MySpeech, LeapListener, MyMain, and MyDrawAutocad. The MySpeech class starts the speech recognition function and sends an event when a speech is recognized. LeapListener first initializes the gesture recognizer and defines all the gestures to be recognized and sends an event when a gesture is recognized. MyMain receives the speech and gesture events, interprets them and sends the right command to AutoCAD. MyDrawAutoCad contains all the functions to draw or manipulate the object or the camera. Figure 1 shows the implemented MMIS structure.

AutoCAD Commands

In AutoCAD, a user can use speech and gesture inputs to execute a command. For speech, the user needs to say the desired command such as "I want to draw a box". With gestures, the user is required to navigate the cursor towards the desired icon and do the clicking gesture. To load the plugin in AutoCAD, the "netload" functionality of AutoCAD has been utilized. Almost all the main functions of AutoCAD have been used such as shapes, color, material, copy, rotate, delete and camera manipulation, etc.

Speech recognition

The speech recognition block starts with the initialization of the Microsoft speech recognition and synthesizer API. The next step is to generate grammar for the speech recognition engine. For grammar building, almost all the main functionalities of AutoCAD has been incorporated in the grammar along with a simple sentence structure. After successful initialization of the speech recognition API and detection of the audio input device, the speech recognition process starts. When a speech is detected with a reasonable confi- dence level, the event is sent to the main block for further interpretation. Figure 2 shows a block structure of the speech recognition process with the corresponding events.

The speech recognition module has some limitations that have to be considered to effectively translate speech into text, such as noise, syllable lengths, and clarity of speech by the user.

Gesture recognition

In this project, the right hand has been used to control the mouse cursor: when the right hand is closed and then opened, it simulates the click of the left mouse button. The left hand has been used to manage the camera view. An event will be sent when the system recognizes that the hand is moving horizontally or vertically or the hand rotates or the hand is closed or open. The opening and closing of the left hand have been used to activate or deactivate the movement of the camera. To recognize gestures, the Leap Motion sensor and its SDK have been used. The Leap Motion sensor has the ability to recognize gestures, identify hands, the number of fingers, the grasping strength, the velocity and direction of movements along with yaw, roll and pitch. The velocity and movement are manipulated to control the cursor in the X and Y directions. The main block receives the speech and gesture events and interprets them to apply the correct AutoCAD commands.

EVALUATION

We evaluated the usability of the system using both quantitative and qualitative assessments. Every user performed two experiments, first using the keyboard and mouse inputs, and second using speech and gesture inputs. After the experiment, user feedbacks were collected through a questionnaire. This questionnaire includes questions to measure the perceived user performance, fa-tigue and cognitive load. The time required for completing the whole experiment is 60-90 minutes per user depending on how familiar the user is with AutoCAD.

Description of the experimentation

The first experiment is to draw a chair using the keyboard and mouse in AutoCAD. For participants who did not know AutoCAD, a step-by-step guide was provided to draw the chair. They had to manipulate a camera view to be able to draw the chair correctly.

For the second experiment, the participants had to get familiar with how to manage both hands: the right hand to simulate the mouse and the left one to control the camera view. Then, they could start to draw the chair. For this experiment, written speech or gesture instructions were also provided.

Testing the application

To evaluate the system performance and find out if it is easier to draw a chair using speech and gestures than using a keyboard and mouse, a log has been created to store the experimental data, which contains the history of commands. Thus, we are able to extract the following information: To evaluate the system, eight individuals (6 men and 2 women) were selected for the experimentation and none had prior knowledge of AutoCAD. All of the participants were computer science students and academics between 20 and 50 years old. All were foreigners but spoke English fluently. At the end of the experiment, the participants were expected to fill in a questionnaire to assess the qualitative performance of the system. In the questionnaire, each question is asked twice, in order to compare their status when performing the task with the keyboard and mouse and with gesture and speech. There are a number of questions related to the performance of the commands, fatigue felt and the participants' perception in interacting with a computer.

•

Log file evaluation

A quantitative analysis has been performed using the data recorded in the log file of each set. Half of the users completed the task in 30 minutes and half took 45 minutes. No user finished drawing the chair by gesture and speech, since they gave up. Those who completed in 45 minutes drew with high precision and the other group drew the chair without obeying the guidelines.

With the log file, we were able to extract information about speech recognition. Figure 3 illustrates different audio signal issues identified during the experiment. 88% of the audio signal issues originated from the signal being too soft -meaning that a soft voice caused too much attenuation on the signal. 9% of the audio signal issues originated from the signal being too noisy. The rest of the audio signal issues originated from being either too loud, too slow or too fast. Figure 4 shows the comparison between recognized, rejected and hypothesized words. Almost 77% of words were hypothesized (detected with low certainty), 14% were rejected and only 7% of words were accepted. The main problem in speech recognition was the hesitation in participants' voice, while speaking. The system expected a complete sentence but the participant expressed only the portion of the sentence such as a number to define the size. Therefore, the system misunderstood the words and even recognized the word "zoom", when the user did not say anything. Figure 5 shows the percentage of sentences recognized and rejected for drawing or manipulating the object. In general, the speech signals were highly hypothesized. It has been noticed that the participants found hard to use speech recognition. The system recognized the words "Draw" (27%), "Copy" (33%) and "Material"(29%) rather well, but "Size", "Height", "Depth", "Scale", "Color", "Radius" have less than 10% recognition rate. It was not possible to exploit the data collected in the log file for gesture recognition. However, we analysed the video records to identify how comfortable the users were through observation. We found that almost none was comfortable with camera manipulation; sometimes the system recognized the hand closed as hand open, even if the hand was partially closed. On the contrary, the system did not recognize the hand closed for the clicking gesture. It was hard for the user to specify the size by using gestures and for left-handed users, it was very difficult to control the mouse.

Through the questionnaires, we concluded that, in general, it was not easy to draw the chair and manipulate the camera in AutoCAD, but it was easier to perform these actions using a keyboard and mouse rather than gesture and speech. The users felt more exhausted while using gesture and speech than using a keyboard and mouse. For the users, it was more natural to use a keyboard and mouse than speech and gesture. They were more satisfied by the response of the computer and more engaged. They felt more frustrated by gesture and speech inputs but appreciated the help and

CONCLUSION

In this paper, a multi-modal system has been presented that utilizes speech and gesture inputs to draw a 3D object in AutoCAD, using a Leap Motion and a microphone. After experimentation and evaluation, we found that speech and gestures are well-coordinated in human to human communication. Unfortunately, it is not the case with the devices that are used to interact with computers in MMIS. Our results indicate that performing a task using speech is perceived exhausting, when there is no shared vocabulary between a human and a machine, and the usability of traditional input devices supersedes the one of speech and gestures. Only a small ratio of participants, less than 7% in our experiments were able to carry out the tasks with appropriate precision.

Drawing with precision in a modeling software is more complex than expected. The speech recognition process is exhausting, when the system works slowly and does not respond properly. Speech recognition requires a simple grammar and a quiet environment to reduce the noise. Gestures seem to be more natural and less tiring to use in human-computer communication, if the users are able to use both hands, instead of one hand only. The system has to offer several gestures for the same action in order to satisfy most users. Even though the system was functional, we still noticed that it has sometimes lost track of gestures. People would prefer more natural interaction such as gesture and speech, if the performance of the equipment for the interaction could satisfy a standard level of operation. However, integration of a Leap Motion, speech, and AutoCAD did not match this standard.

Figure 1 :

 1 Figure 1: MMIS structure of the implemented system

Figure 2 :

 2 Figure 2: Speech recognition module block diagram

  Number of detected speech commands • Number of recognized speech commands • Number of low-confidence speech recognition • Number of hypothesized speech commands • Number of rejected speech commands • Number of audio signal issues

Figure 3 :

 3 Figure 3: Audio signal issues during speech recognition

Figure 4 :

 4 Figure 4: Percentage of hypothesized, rejected and recognized words

Figure 5 :

 5 Figure 5: Up: detected sentences for drawing; down: detected sentences for manipulation

Table 1 :

 1 Speech and corresponding AutoCAD commands Speech AutoCAD commands Box, rectangle, square, bars, layer

		BOX
	Cylinder, tube	CYLINDER
	Cone	CONE
	Wedge	WEDGE
	Sphere	SPHERE
	Torus, donut	TORUS
	Arc	ARC 3 points
	Extrude	EXTRUDE
	Fillet, FilletEdge, round	FILLETEDGE
	Thicken	THICKEN
	Move, Displacement	MOVE
	Copy, duplicate, clone	COPY
	Remove, Delete	DELETE
	Scale	SCALE
	Rotation, rotate	ROTATE
	Undo	UNDO
	Finish	ENTER (to finish an ac-
		tion)
	Select all	SELECTALL
	Select last	SELECTLAST


Thibault Porssut
email: thibault.porssut@epfl.ch

Jean-R Émy Chardonnet
email: jean-remy.chardonnet@ensam.eu

Asymetric Telecollaboration in Virtual Reality

Keywords: Telecollaboration, CAVE, HMD H.5.1 [Information Interfaces and Presentation]: Multimedia Information Systems-Artificial, augmented, and virtual realities; H.5.3 [Information Interfaces and Presentation]: Group and Organization Interfaces-Computer-supported cooperative

We present a first study where we combine two asymetric virtual reality systems for telecollaboration purposes: a CAVE system and a head-mounted display (HMD), using a server-client type architecture. Experiments on a puzzle game in limited time, alone and in collaboration, show that combining asymetric systems reduces cognitive load. Moreover, the participants reported preferring working in collaboration and showed to be more efficient in collaboration. These results provide insights in combining several low cost HMDs with a unique expensive CAVE.

INTRODUCTION

The introduction of low cost virtual reality (VR) solutions, such as HTC Vive, allows considering new working methods, among which telecollaboration, for applications such as digital mockup reviews. We present a telecollaboration mode between two VR systems, aiming at improving users performance with reduced cognitive load.

Telecollaboration in VR has been explored in past research. One of the main constraints lies in the data transmission speed [START_REF] Pantelidis | The rave, cave, and collaborative virtual environments[END_REF], which is less an issue now with for example optical fibers. Most of past work use CAVE systems for telecollaboration (e.g., [START_REF] Fleury | Evaluation of remote collaborative manipulation for scientific data analysis[END_REF]). The pros and cons of a two-person collaboration in a CAVE or with two HMDs for collaborative visualization of abstract data has been explored [START_REF] Cordeil | Immersive collaborative analysis of network connectivity: Cave-style or head-mounted display?[END_REF], showing comparable experiences in both systems, however, here, we do not look at comparing two systems, but at combining two different systems together, on a concrete task. Heldal et al. evaluated collaboration for solving a puzzle [START_REF] Heldal | Evaluating collaboration in distributed virtual environments for a puzzle-solving task[END_REF] but limited to evaluate the performance of two persons together, without knowing the performance of a person alone. Mortensen et al. realized a study on asymetric telecollaboration for a task requiring two persons, and showed a correlation between copresence and performance [START_REF] Mortensen | Collaboration in tele-immersive environments[END_REF].

We present here a first study of telecollaboration between two persons using different VR systems: a CAVE system and a low cost HMD. The study aims at evaluating the interest of combining two different (asymetric) systems to improve users performance with reduced cognitive load. We hypothesized that combining asymetric systems in a collaborative way improves indeed users performance.

TELECOLLABORATION ARCHITECTURE

To achieve distant collaboration, we chose to define a server-client type architecture: the CAVE, a high cost, non transportable system, will be defined as the server whereas the HMD, a low cost, wearable device, thus easily duplicable, as a client.

Hardware

The CAVE used here is a CAVE2 TM [START_REF] Febretti | Cave2: a hybrid reality environment for immersive simulation and information analysis[END_REF], equipped with 72 LCD screens with a 37 megapixels total resolution and passive stereoscopy. We installed a microphone on the floor to let the user interact with a remote collaborator. On the contrary of more classic CAVEs, the CAVE2 does not have any projected floor, therefore full immersion is not possible.

The HMD used here is a HTC Vive, a low cost HMD, with a Lighthouse tracking system allowing to move naturally in a room. The user has two tracked controllers, one in each hand. A microphone is already integrated in the HMD.

Software

All the developments were made under Unity. Device networking was done using UNET, the Unity network add-on, while communication between the two remote users is achieved using Skype.

The application is a Puzzle Game, where the goal is to build a figure with virtual colored cubes placed in a virtual environment randomly (see Figure 1). The figure has to be built in a specific place (a red circle) in a limited time (10 min). Instructions are written on a virtual board. An application has been built for both systems.

In the CAVE2 version, the user holds a wand modeled by a hand in the game. He can navigate by walking within the physical space of the CAVE2, by teleportation or by using the wand's joystick. The virtual hand allows cube manipulation: when a cube is touched, it changes color. In the Vive version, users use both hands for manipulation and navigation can be achieved by walking or by teleportation (which is a good alternative to reduce cybersickness).

The differences between the CAVE2 and the Vive versions come from a pure industrial constraint. The CAVE2 is indeed delivered with only one wand with joystick-based displacements by default. Therefore, we wanted to respect basic technical constraints in order to simulate real configurations CAVE2 users usually face.

ASSESSMENT PROTOCOL

18 people (10 men and 8 women, aged between 18 and 30) participated in the experiment (9 sessions, one per pair of participants).

A device, either the CAVE2 or the Vive, is assigned randomly to a participant and is kept by the participant throughout the experiment which is divided into three tasks: task 1 to get familiar with the device, task 2 where the participant is alone to complete the puzzle, and task 3, where he completes the puzzle in remote collaboration with another participant. Both participants can speak to each other and see each other through avatar representation in the virtual scene. The figure to complete in each task is different to avoid learning effects.

We use both objective and subjective measures to evaluate the effect of collaboration. As subjective measures, we provide several questionnaires: one to know whether the participants have prior experience with VR and video games, potential handicaps and diseases that could affect their performance, and another as a feedback questionnaire on the experiment. We also use the NASA-TLX (Task Load Index) [START_REF] Hart | Development of nasa-tlx (task load index): Results of empirical and theoretical research[END_REF] to evaluate the different cognitive loads (mental, physical, temporal loads, effort, frustration and performance). As objective measures, we measure the completion rate: knowing the total number of cubes to place, we count the number of cubes a participant was able to place at the end of each session.

DATA ANALYSIS 4.1 User Experience Questionnaire

From the user experience questionnaire, half of the participants play video games regularly. Task 1 was designed to reduce the gap between participants (gamers and non-gamers).

NASA-TLX

We measured a TLX per task. The results in both situations (single -task 2 -and collaborative -task 3) are depicted in Figures 2.a and 2.b for participants with the Vive and the CAVE2 respectively.

The Friedman test shows that the effort demand either with the Vive or the CAVE2 is similar for both tasks (χ 2 Vive = 0.50, χ 2 CAVE2 = 1.00, p > .05). Collaboration shows to have a significant effect on temporal (χ 2 = 5.44, p < .05) and mental demands (χ 2 = 4.50, p < .05) with the Vive. We suppose that the high level of frustration with the CAVE2 in task 2 (M = 66.7) comes from the absence of projected floor, complicating task accomplishment.

Hence, collaborative work allows reducing cognitive loads, thus reducing overall cognitive workload, significantly with the Vive (χ 2 = 4.50, p < .05). The participants felt more confident in collaboration than alone. Note that with the CAVE2, the workload did not reduce significantly, we suppose again that the CAVE2 configuration was not ideal and complicated the tasks.

Completion Rate

Figure 3 shows the completion rates for each task with each device. After conducting a one-way within-subject ANOVA, there was a significant effect of the task type (single or collaborative) on the performance : F(2, 24) = 10.99, p = .0004. Post-hoc comparisons showed that collaboration significantly improves performance, whatever the device (Vive: t(8) = 6.05, p = .0001 ; CAVE2: t(8) = 4.85, p = .0006). Note that from TLX measures, performance is perceived not to change significantly. Also we remarked that gamers did not perform better than non-gamers.

The difference in completion rate between tasks 2 and 3 is more important (but not in a significant way) for CAVE2 participants (M = 40.3) than for Vive participants (M = 28.0). It is possible that again one reason comes from the absence of projected floor in the CAVE2, forcing participants to move frequently and loose time.

Feedback Questionnaire

No major problem has been reported by the participants (Vive and CAVE2). Most of them (89%) felt no or very little cybersickness.

We observed that overall, collaborative work is preferred to single work (78%). Surprisingly, many CAVE2 participants (28%) preferred working alone rather than in collaboration, on the contrary of Vive participants (all reported preferring working in collaboration). This observation can explain higher TLX indices for CAVE2 participants in both tasks.

CONCLUSION

We presented a first collaboration study using two asymetric systems. Collaboration allows reducing cognitive load. Completion rates show that users performance is enhanced, though from the TLX users reported a level of difficulty similar in both tasks.

We are willing to explore in a near future asymetric telecollaboration using different technologies for applications such as concurrent engineering, considering presence and embodiment.

Figure 1 :

 1 Figure 1: Collaborative puzzle construction session between a Vive user (left) and a CAVE2 user (right).

Figure 2 :

 2 Figure 2: TLX for each task with: a. Vive, b. CAVE2.

Figure 3 :

 3 Figure 3: Completion rates for both tasks.

ACKNOWLEDGMENTS

The authors wish to thank Mechdyne and the EVL at University of Illinois at Chicago for their help in using the CAVE2.


Emanuele Giordano

Chin-Ee Ong

LIGHT FESTIVALS, POLICY MOBILITIES AND URBAN TOURISM

Keywords: light festivals, serial reproduction, tourism cities, policy mobility, urban tourism, Lyon

This article is an attempt to introduce a policy mobility perspective in the field of tourism. Focusing on the development of light festivals around the world, the paper shows how tourism policies are not reproduced in a straightforward serial way but they are constantly adapted under local circumstances. As such, the paper reveals that despite the recent accounts on the shift toward forms of urban tourism characterized by a quest for a more mundane and authentic experience of the city, elite-endorsed and often top-down attempts to re-stage the tourism city are still persistent and points to the existence of a wider range of tourism motivations in which the simulation and the staging of the tourism experience are accepted and appreciated.

Introduction

The use of illumination as form of spectacle and as tourist attraction is not a recent fact [START_REF] Edensor | Illuminations, Class Identities and the Contested Landscapes of Christmas[END_REF][START_REF] Gravari-Barbas | A la conquête du temps urbain : La ville festive des 24 heures sur 24[END_REF]. Yet in the last years, this trend has taken on an unprecedented relevance, and the use of illumination to attract tourists now extends around the world [START_REF] Guo | The Development of Urban Night Tourism based on the Nightscape Lighting Projects -A Case Study of Guangzhou[END_REF]. Particular examples of this phenomenon are light festivals. Events characterised by the installation into the public place of artistic lighting installations and the projections of holograms on the buildings' façades, light festivals have become an increasing feature of city entertainment and tourism and have produced spectacular, fantastic urban landscapes, which attract millions of visitors yearly [START_REF] Alves | Art, Light and Landscape New Agendas for Urban Development[END_REF], Ederson, 2014). Crucially, the extraordinary success experienced by light festivals like Lyon or Eindhoven has brought numerous local authorities to implement similar events. While Lyon's Fête des Lumières, created in 1999, was arguably the first light festival, more than 100 festivals are nowadays active all around the world.

Accounts on how creative strategies and paradigms have been copied and circulated from one city to another are not new in tourism studies [START_REF] Evans | Hard-Branding the Cultural Cityfrom Prado to Prada[END_REF][START_REF] Richards | Developing creativity in tourist experiences: A solution to the serial reproduction of culture?[END_REF]. However these policy mobilities perspectives are traditionally characterized by arguments of serial reproduction that tends to conceptualize the process of policy circulation like a linear adoption of exogenous prescriptions copied by another city. As such they tend to share a negative viewpoint on the results of this strategy of policy emulation as accordingly to many authors the uncritical emulation of a few renowned 'best practice' cases, often results in unattractive forms of serial reproduction that led to increasing 'placelessness' [START_REF] Smith | Space, Place and Placelessness in the Culturally Regenerated City[END_REF]. Conversely, this corpus of work argues that the counterproductive effects produced by these attempts to stage the tourist city are generating a shift toward new forms of tourism characterized by a an active search for a more 'authentic' experience of the city, often associated with a stronger engagement with the distinct characteristics of the everyday life of the destination [START_REF] Pappalepore | Prosuming creative urban areas. Evidence from East London[END_REF][START_REF] Richards | Creativity and tourism: The State of the Art[END_REF][START_REF] Richards | Creativity and Tourism in the City[END_REF][START_REF] Richards | Developing creativity in tourist experiences: A solution to the serial reproduction of culture?[END_REF][START_REF] Tan | A model of "creative experience" in creative tourism[END_REF]). Yet, the emergence of light festival events at a global level does not conform to such theorisation. While almost all the light festivals around the world experience a constant growth both in revenues and number of visitors, these events are far from being forms of tourism based on endogenous creative capital. Despite the fact that most of these events claim to be inspired by local traditions and know-how, recent accounts that have emerged in French literature have shown that international consultants and networks play a key role in the spread of the light festival concept around the world [START_REF] Hernandez | Comment l'illumination nocturne est devenue une politique urbaine : la circulation de modèles d'aménagement de Lyon (France) á Puebla, Morelia et San Luis Potosi[END_REF]. Crucially here we do not contend that all light festivals are necessarily large events, instrumentally and artificially organized by city managers and marketers in order to attract tourists and shoppers and contribute to the rebranding of place. As Steven and Shin (2012) have pointed out this narrative does not take into account the proliferation of smaller, more locally organized and participatory festivals that are often not motivated by commercial drives but instead support "the redefinition, rediscovery and expansion of local social file and meanings of place" (p.1). [START_REF] Edensor | The Rich potentialities of Light Festivals[END_REF] has recently remarked that several light festivals around the world lack the commercial drives and top-down administration of the large urban events and instead contain potential to engender positive values and outcomes while attracting numerous visitors. Yet, at the same time, we argue that the spectacular global proliferation of light festivals in recent years is not fully understandable without considering the role of international networks of experts and lighting professionals and how commercial imperatives largely prevail in many settings.

As such, rather than adopting a traditional "serial reproduction" viewpoint towards understanding light festival and urban tourism policies, the paper employs a more nuanced perspective to examine the mechanisms, actors, concepts, strategies and artefacts related to light festivals which have (or have not) circulated globally. Following [START_REF] Ashworth | Urban Tourism Research: Recent Progress and Current Paradoxes[END_REF] argument on the need for an approach to urban tourism that interconnects with the wider domain of social sciences, we make a cross-disciplinary connection with urban studies and explore the progressive establishment of light festival at a global level adopting a "policy mobilities" perspective (McCann, 2011:109). Rather than considering the diffusion of light festival as the results of a linear reproduction, the process is approached as a socially constructed one, associated with increasingly intense forms of institutional layering and embedded power relations.

Such a perspective allows us to go beyond the vision of a simple serial reproduction of tourism policies and to reveal the increasing "local globalness" (McCann, 2011:120) of tourism policy transfer. Even if the circulation of light festivals reflects a strategy of policy emulation, largely inspired by few "best practice" cases, these events are not replicated in a serial and unproblematic way, but are selectively acknowledged and appropriated by local actors. Crucially this process of adaptation allows light festivals to be successfully transplanted from one city to another, escaping the problem traditional related to the "serial reproduction" process.

At the same time revealing how tourism policies could effectively circulate from one city to another, the paper shows how rather than simply a move towards a "new urban tourism" [START_REF] Füller | Stop being a tourist!' New dynamics of urban tourism in Berlin-Kreuzberg[END_REF] characterized by the increasing quest for a more mundane and relational experience of the city, the multiplication of light events at a global level points to still existing sets of tourism staging and more importantly, an elite-endorsed and often topdown re-staging of the tourism city for the tourist experience.

The paper first introduces how, in the field of urban studies, the analysis of the process of policy circulation has evolved from a serial reproduction perspective to a more articulate "policy mobility" approach. The next section examines the mechanism and network that have allowed light festival concepts and artefacts to travel globally from Europe to the other continents. Next, the paper discusses how the concept of light festival is not reproduced in a completely or straightforwardly serial way but is constantly adapted under local circumstances. Finally, the paper offers a cultural perspective on how urban tourism, despite the rise of forms of tourism characterized by a quest by visitors for 'typical' mundane experiences in everyday spaces of the visited city, goes beyond this search of "authenticity" and points to the existence of a wider range of tourism motivations in which, under specific conditions, simulation and staging of the tourism experience are still accepted and appreciated.

Serial reproduction, policy mobilities and tourism

The de-industrialisation of cities and the exacerbation of the inter-urban competition had produced a set of circumstances in which policy-makers throughout Europe and beyond have desperately sought to explore the possibilities for a post-industrial future. Following the rise of the Creative City paradigm, numerous cities have seen, in the development of creative strategies and cultural investment in capital-intensive projects, a tool to distinguish themselves in a globalized world characterized by a growing inter urban competition. Such an idea has also permeated the field of tourism, as culture has been seen as an increasingly important element of tourism experience in the city and as a way to gain local distinctiveness.

As [START_REF] Zukin | The Cultures of Cities[END_REF]1-2) writes, "with the disappearance of local manufacturing industries and periodic crisis in government and finance, culture is more and more the business of cities: the basis of their tourist attractions and their unique competitive edge". In this context of intense competition, policy makers are constantly under pressure to develop new innovative polices and therefore are perpetually in search of new trends and best practices that can be applied quickly locally.

As a result, many new ideas or policy innovations are quickly transferred from one city to the others with increased regularity [START_REF] Peck | Exporting workfare/ importing welfare-to-work: Exploring the politics of Third Way policy transfer[END_REF][START_REF] Theodore | Searching for best practice in welfare-to-work: The means, the method, and the message[END_REF]. Yet in the field of tourism, this strategy of "fast policy" has been often accused to be counterproductive as the race to produce distinction often has resulted in the adoption of similar creative development models. For instance, Richards (2014:119) asserts that "adopting forms of 'fast policy' and copying ideas from other 'creative cities' through 'policy tourism', the result is often a form of serial reproduction, unattractive to the very tourists cities seek to attract". According to many authors, the growing ineffectiveness of this strategy of policy emulation is contributing to the decline in staging and to the emergence of a trend toward forms of tourism based on local and embedded knowledge that are able to offer experiences perceived as more authentic by tourists [START_REF] Maitland | Everyday life as a creative experience in cities[END_REF][START_REF] Pappalepore | Prosuming creative urban areas. Evidence from East London[END_REF]Richard, 2014;[START_REF] Richards | Developing creativity in tourist experiences: A solution to the serial reproduction of culture?[END_REF][START_REF] Tan | A model of "creative experience" in creative tourism[END_REF]. With regard to this, Richards asserts that urban tourism is moving "towards more intangible culture and greater involvement with the everyday life of the destination" (2011:1255) a process that allows visitors and tourists to "escape from the serial reproduction of mass cultural tourism, offering more flexible and authentic experiences which can be co-created between host and tourist" (2011:1255).

While reviewing and discussing the ways in which creative gurus' ideas, such as Richard Florida and Charles Landry, has been quickly and uncritically adopted by numerous cities, this abovementioned literature resonated with the broader corpus of work in urban studies regarding policy mobilities and policy emulations without actually referencing them (for example, [START_REF] Bunnell | Urban Pulse-A Geography of Serial Seduction: Urban Policy Transfer from Kuala Lumpur to Hyderabad[END_REF][START_REF] Bunnell | Antecedent Cities and Inter-referencing Effects: Learning from and Extending Beyond Critiques of Neoliberalisation[END_REF][START_REF] Mccann | Urban Policy Mobilities and Global Circuits of Knowledge: Towards a Research Agenda[END_REF][START_REF] Mcneill | The Global Architect: Firms, Fame and Urban Form[END_REF]. Here, we argue that such sidelining of a broader literature on urban policy emulations may have contributed to this focus on an increase in personal tourism networks in tourism places.

Crucially the phenomenon of policy learning and policy transfer should not be understood as a simple process of serial reproduction of standardizes policies around the world. Analysis of policy transfer has evolved from the perspective of a linear transaction to a much wider and flexible notion of policy mobilities. As remarked by McCann (2011: 111) "policies, models, and ideas are not moved around like gifts at a birthday party or like jars on shelves, where the mobilization does not change the character and content of the mobilized objects". Rather they are continuously muted and transformed by the specific local circumstance under which they are implemented.

In the last years, numerous accounts have explored the process of circulation and adaptation of different typologies of policies like creative city programs [START_REF] Lee | Global Urban Frontiers through Policy Transfer? Unpacking Seoul's Creative City Programmes[END_REF] and the so called Bilbao and Barcelona models [START_REF] González | Bilbao and Barcelona 'in Motion'. How Urban Regeneration 'Models' Travel and Mutate in the Global Flows of Policy Tourism[END_REF] from this perspective. Yet, until now, very few attempts have been made to adopt a policy mobility approach in the analysis of the mobility of tourism strategies and events. As a result, tourism studies are still dominated by a more simplistic serial reproduction perspective. This vision falls short of recognizing the increasingly "local globalness" of urban policy transfer (McCann, 2011:120).

Policies do not flow around the globe unchanged but they experienced a process of adaptation to the peculiar economic, political situation in which they are adopted. Crucially, this process allows them to be successfully transplanted from a city to another as demonstrated, for example, by the proliferation of events like the Nuit Blanche. Yet, even if partially adapted to the local condition of each case, these tourism city policy travels reflect a "further serialisation and commodification of city spaces through an international brandtouristic rather than community/cultural-based" (Evans, 2012:47). Alongside development of new relational forms of tourism, the proliferation of expert-managed cultural events, often with the collaboration of international networks and under a recognized brand, remains a major strategy adopted by both capital and smaller cities showing how, instead of a decline in staging and a rise of co-creation in tourism cities and their associated tourist experience, efforts and attempts at re-staging the tourist experience and in the construction (usually topdown, elite-centred) at tourism cities are still present and persistent.

Research Methods

Research began by unraveling the key networks and organizations that have allowed festival concepts and artifacts to travel globally. Previous research on the international circulation of light festivals around the world highlighted the role of Lighting Urban Community International organization (LUCI) which is located in Lyon and of the city of Lyon itself in this process (Fernandez, 2009). Initial contacts with these organizations and accademics that have previously worked on this topic have on one hand confirmed the role of this associations in the global circulation of light festivals, on the other hand revealed the existence of another network, the International Lightfestival Organization (ILO) which instead is located in Eindhoven. Once these networks were identified, the research employed a mix of methods and data sources to explore the amount and nature of the global circulation of light festivals and light festivals' contents and rationalities vary and evolve accordingly to local situation and aspirations.

When the research began, no centralized or comprehensive dataset on existing light festivals was available. Some of the organizations have compiled their own data set but they were limited to the cities that participate in their network. As such we compiled ours own dataset that combines the lists that different stakeholders accepted to share with us and data archived though further archive and internet researches. In compiling the dataset we utilize a large definition of light festivals. Some of the stakeholders considered as light festivals only events characterized by the presence of artistic light installation, while events characterized by lighting projection mapping (a projection technology used to turn objects, often architectural feature, into a display surface for video projection) were considered a different type of events.

Due to the fact that most of the light festivals, including Lyon, employed both these types of installations and the Lighting Urban Community International organization does not adopt this distinction we employed the broader definition. Crucially, the compiled data do not offer a complete overview of all the existing light festivals around the world but presents a useful snapshot of the geographical spread and quickness of the spread of temporary light events at a global scale.

The circulation of light festivals' concepts and artefacts at global scale was uncovered through a mix of methods and data source. The diffusion network was uncovered through interviews with several key actors. Members of all the three networks and organization involved in the circulation of the light festival were interviewed about the actions and initiatives they developed, what kind of visitors participate, what were their motivations and what they were normally interested in. At the same time, the way in which light festivals light festivals' contents and rationalities vary accordingly to local situation and aspirations was uncovered through semi-structured interviews with light festival directors who were questioned about: 1) which events or ideas inspired the creation of the light festivals, 2) which features differentiate their light festival from another and which features are similar, 3) how their light festivals have evolved over time and 4) which international or local elements have caused this evolution.

The festivals of Lyon and Eindhoven were selected due to their status of international benchmarks, often cited as an example as a source of inspiration and due to the their status as "urban policy tourism" destinations. In particular, the fact that the Lyon's Fete des Lumières has been hired by several cities around the world to organize new light festivals is of particular interest in the framework of the research. At the same time, the fact that these two festivals are some of the oldest allow us to investigate how they have evolved according to the local conditions for almost twenty years. The festival of Barcelona was chosen to offer the insights of a recently organized festivals. These information were complemented by interviews with light designers who were selected for having showcased their light installation to several light festivals around the world. All interviews were formal and prearranged. They were recorded, transcribed and were then subjected to a mixture of inductive and deductive analysis (Yin, 2003). The interviews were complemented by the data analysis of secondary information, mainly the organizations' and light festivals annuals reports and academic literature.

Festival of lights and the circulation of urban lightscapes

The role of Lyon and international networks

Numerous studies have recognized that festivals and cultural events can enhance destination image, and promote and stimulate tourism development [START_REF] Quinn | Arts Festivals and the City[END_REF]. A particular manifestation of these 'eventful cities' [START_REF] Richards | Eventful Cities: Cultural Management and Urban Revitalisation[END_REF] are the late night cultural festivals [START_REF] Evans | Hold Back the Night: Nuit Blanche and All-Night Events in Capital Cities[END_REF][START_REF] Jiwa | Light Night: An 'Enlightening' Place Marketing Experience[END_REF]. These events has been perceived by local authorities on one hand as a valid alternative to the traditional night time economy based on drinking and on the other as an attraction capable to extend temporally and geographically the distribution of tourism activity. Particular examples of this type of festivals are the light festivals.

The most well-known light festival is without doubt the Fête des Lumières in Lyon.

The first city to fully adopt the new lighting principle developed in the last '80, Lyon rapidly became an urban laboratory in which new lighting design methodology and tools were firstly developed. A new generation of lighting designer, the so called Lyon's school, emerged playing a fundamental role in spreading the new urban lighting principles around the world while Lyon started to be consider as an international benchmark in term of urban illumination [START_REF] Hernandez | Comment l'illumination nocturne est devenue une politique urbaine : la circulation de modèles d'aménagement de Lyon (France) á Puebla, Morelia et San Luis Potosi[END_REF]. Therefore in 1999 Lyon's local authorities decided to exploit the existing know-how in terms of lighting design and policies to enhance city image and tourism appeal by creating the Fête des Lumières. The festival takes place each year three nights in December around the Christian Feast of Immaculate Conception and draws on a tradition of putting lit candles on window ledges to propitiate the Virgin Mary. During the festival, the installation of lighting displays, spectacles and large-scale installations, including coloured and dynamic lighting created by international artists transforms the city into a phantasmagorical landscape and creates affective and evocative atmospheres. The Fête des Lumières has had an immediate success, transforming a city traditionally perceived as boring and unattractive into one of the most important tourist destination of France that in the three days of the festival is visited by millions of tourists. Lyon's success has acted as a catalyst in the progressive development of new light festivals. An increasing awareness of the potential of lighting festivals as touristic attraction and for city marketing has emerged. Accordingly, numerous cities in the last years have organized their own light festivals due to their capacity to attract people. As Edensor remarks, "the Fête des Lumières acts as an international showcase to demonstrate the potential for illumination to transform space and is a global magnet for those planning light festivals" (Edensor, 2014 p. 88). In the last decade, this phenomenon has continuously expanded and new light festivals have been developed starting from lighting technology-based trade fair in Frankfurt, educational programme for student in Alingsås or from the strong technical history of local lighting manufacturers such as Philips in Eindhoven and ERCO in Lüdenscheid [START_REF] Pearce | Painting the town red[END_REF][START_REF] Schielke | Light Matters: Europe's Leading Light Festivals[END_REF]. International), an international network bringing together cities and lighting professionals engaged in using light as a major tool for urban, social and economic development, with a concern for sustainability and environmental issues. The association has since been wellentrenched in Lyon and has the Deputy Mayor of Lyon as its permanent Honorary President.

It technically supports cities that want to develop urban lighting design policies and organizes international conferences that bring professionals, lighting companies and public authorities from all over the world together to discuss issues of innovative lighting technologies, policies and events. Since the beginning, festivals of light have been a main focus in LUCI activities.

The association created a permanent commission to explore the potential benefits of light festivals for host cities and how the success of such events could be measured and developed a toolkit to support and justify the organization of such events. It also organized a support service that provides assistance to cities from developing countries that require support to conceive and /or implement new city lighting strategies and initiatives. According to the association, nearly 40 of its 70 city members are organizing some form of lighting festivals, all of them created after the association foundation in 2002 [START_REF] Pearce | Painting the town red[END_REF].

To facilitate the development of light festivals, the LUCI association developed a light festival database opened to cities and lighting professionals that provides key information as budget, organizer, dates, artist involved on the festivals organized by the network members in 2014. Moreover, every year LUCI association organizes conferences and events that unite local authorities, lighting professionals and academics to discuss challenges related to lighting politics and events. Through the siting of most of these activities in Lyon, LUCI not only provides "key relational sites that are central to the social process of teaching and learning about policy and, thus, to the contingent, cumulative, and emergent knowledge production processes that co-constitute urban policy mobilities" (McCann, 2011 p. 120) but also reinforces the city's role as international benchmark. For instance, since 2012, LUCI in collaboration with the city of Lyon organized the "Lyon Light

Festival Forum" an annual discussion of light festival organisation as part of the Fête des Lumières. Local authorities and professionals come from all over the world to the French city to visit the festival and learn from its experience. During the three editions that have been developed until now, more than 200 delegations from all over the world attended, sometimes resulting in the signing of collaboration agreements to support the development of new light festivals [START_REF] Lyon | Fête des Lumières : des délégations étrangères au rendez-vous[END_REF].

However these forms of "urban policy tourism" [START_REF] González | Bilbao and Barcelona 'in Motion'. How Urban Regeneration 'Models' Travel and Mutate in the Global Flows of Policy Tourism[END_REF](González, :1398) ) are not only limited to the Lyon festival but is of interest to all the most important light festivals. For instance, the project manager of the Eindhoven Glow festival revealed that every year during the festivals he received several request from local authorities to visit the festival and have the opportunity to discuss about the advantages and problem related to the organization of such events.

"We have a lot of requests during the whole festival from cities that want to learn from our experience…not only from Europe but also from other continents" (Interview, June 2015).

Alongside this form of study visit, a more stable network allows ideas, strategies and artefacts problems and best practices, it also incentives the participation of the members to all the light festivals that compose the network. In doing so, it promotes the development of key relational sites that are a crucial element in the process of teaching and learning that characterizes policies mobility. Moreover, the organization not only promotes the collaboration between festivals through the circulation of idea but also supports the co-funding of the creation or transportation of art installation that will be exposed in different festivals.

Crucially the role played by these international networks reaffirms [START_REF] Stone | Transfer Agents and Global Networks in the 'Transnationalization' of Policy[END_REF] view that policies not only circulates through bilateral relation between public authorities but that also through the actions of international organizations and/or transnational non-state actors. However, alongside these international actors, the role of local authorities in the process of policy circulation remains central [START_REF] Lee | Global Urban Frontiers through Policy Transfer? Unpacking Seoul's Creative City Programmes[END_REF][START_REF] González | Bilbao and Barcelona 'in Motion'. How Urban Regeneration 'Models' Travel and Mutate in the Global Flows of Policy Tourism[END_REF]. For instance, the city of Lyon not only acts as a member of international networks but has autonomously developed forms of policy boosterism and acts as a "transfer agent" (Stone, 2004:545), giving Oceania and Asia and some of them like the Sydney's Vivid have already gained international relevance. At the same time light festivals are also becoming a metropolitan phenomenon. Originally, light festivals were initially developed by medium and small size cities due to a simpler logistic requirement and the difficulty in quantifying the festivals' benefits in big urban area ̶ a fundamental knowledge to attract sponsor and financial partners [START_REF] Pearce | Painting the town red[END_REF]. However due to the increasing success of light festivals around the world in the last 5 years, cities as Barcelona, Singapore, Dubai, New York and Sydney have also started to organise their own festivals.

Such a trend, constituted within a strategy of developing light festivals as a mass tourism attraction, is motivated by the process of circulation of policies that characterised the increasing competition between cities to attract touristic flows. Underlining such desires for increased recognition, visibility and tourism flows are the workings of aspirations on the part of a constellation of urban actors [START_REF] Amin | Re-thinking the Urban Social[END_REF][START_REF] Appaduria | The Capacity to Aspire: Culture and the Terms of Recognition[END_REF]Bunnell & Goh, 2012;[START_REF] Bunnell | Jakarta in Post-Suharto Indonesia: Decentralisation, Neoliberalism and Global City Aspiration[END_REF][START_REF] Kearns | New Challenges for Urban Governance[END_REF][START_REF] Moser | Circulating visions of 'High Islam': The adoption of fantasy middle Eastern architecture in constructing Malaysian national identity[END_REF][START_REF] Ong | Introduction: Worlding Cities, or the Art of being Global In[END_REF] and the relational effects of urban actants (Bunnell et al., 2012;Ong & du Cros, 2012b). The manager of the Light Festival Organization explicitly recognized how the main motivation that has brought a growing number of cities to organize their own light festival is:

"the great number of visitors in every festival and they grow more and more every year" (Interview, July, 2015).

However this process should not be understood as a simple serial reproduction of a standardized event. Light festivals' contents and rationalities vary broadly accordingly to local situation and aspirations. They tend to be increasingly differentiated in terms of duration and typologies of installations they expose as they focuses on different market segments and scopes ̶ whether as an economically-orientated tourism event or an ambitious fine art exhibition or something in-between [START_REF] Schielke | Light Matters: Europe's Leading Light Festivals[END_REF]. As Edensor remarks (2015a:340) "at a global level, a profuse number of light festivals are being established, varying in scale, intention, venue and design, and ranging from showpieces for the most advanced lighting designs and spectacular techniques to stages for vernacular creativities and local identities".

Crucially, this progressive differentiation reflects not only how the appreciation of particular designs, colours and levels of illumination is culturally inflicted [START_REF] Edensor | Illuminated Atmospheres: Anticipating and Reproducing the Flow of Affective Experience in Blackpool[END_REF] but also local power relations.

For instance, Lyon's Fête des Lumières in the last years has increasingly developed into a mass tourism event, attracting every year millions of visitors in only 3 days. While the desire of local authorities for increased visibility and tourist flows has played an important role in this development, the justification for this shift has been offered by visitors' negative response to the development of a more "creative" and "interactive" kind of festival. In 2004, the organizers decided to change the festival format, in order to reduce the focus on the traditional spectacular and colourful light installations and introduce new and innovative elements into the programmes in order to enhance the visitors' role in the co-production of the event. As such, they decided to present more artistic and interactive light installations, often created by local artists, and to include in the program, participatory workshop and live spectacles designed to be co-created between artists and spectators. However visitors' reactions to this new format were extremely negative. This approach was considered too elitist and " too conceptual, the 2004 edition of the Festival of Lights will remain the worst memory of the festival's history" (Le Monde 2004, cit. in Hernandez, 2010 p.120). As a result, local authorities decided to return to a more traditional format based solely on the adoption of less innovative, easily understandable light installations. While this trend has been clearly appreciated by tourists, as demonstrated by the constant growth of the number of visitors in the following years, numerous light designers express disenchantment toward the festival. For instance, Roger Narboni, a leading figure in light design from both a professional and intellectual perspective [START_REF] Narboni | Lighting the Landscape[END_REF]2012) and the old artistic director of Lyon Fête des Lumières was extremely critical about this trend. In a recent interview, and with reference to the France festival, he stated:

"The program is intended primarily to please and attract the greatest possible number of visitors. In this approach there is no room for the invention of a new urban lighting or to question our relationship with the night space. Nowadays, light festivals are reduced, unfortunately, to the projection of giant images or videos on the facades that transform the city into a shocking night decoration" [START_REF] Lightecture | Roger Narboni, reaprender la oscuridad[END_REF].

However, not all the light festivals have followed the same path toward massification. For instance, the Eindhoven's Glow, another major festival is trying to maintain a more interactive and innovative dimension. As stated by the project manager of the festivals about Lyon's festival, "We absolutely don't want that. We want much more in the art way. It's always a discussion with our board because they want millions of people and we only want the art part." (Interview, June 2015). All the respondents confirmed that local authorities' aspirations to attract a growing number of tourists, often collide with the desire of the directors and organizers to maintain a more innovative and artistic approach in determining the festivals' scale, intentions and design. As a result, each festivals is the final outcome of power relations that are shaped by local, economic and political conditions that are mediate through tourists' responses to the event. The director of Eindhoven festival clearly admits how visitors' reactions, which contrary to Lyon have been positive, have allowed to maintain a more artistic approach "We won (in the discussion with the board) because people are still coming" (Interview, June, 2015). Shaped by every time unique local conditions, the outcome of this struggle varies greatly and constantly provokes the unique recombination of the artistic and organizational elements that constitute such events [START_REF] Alves | Art, Light and Landscape New Agendas for Urban Development[END_REF].

This process of differentiations does not imply that the festivals are evolving in Despite the fact that the diffusion of light festivals around world is produced by a strategy of policy emulation, largely inspired by few "best practice" cases (Lyon, Turin, Eindhoven) these models are not replicated in a straightforward and unproblematic way, but are selectively acknowledged and appropriated by local actors. For example, while the director of the LLUM festival of Barcelona admits that she was inspired by her visits and contacts with the organizers of Lyon and Turin festivals she also acknowledges that the Barcelona event is not a straightforward reproduction of one of these events but rather a combination of some elements inspired by these two festivals with the local expertise in term of light design and events management. The result is an event based on light installation, which aspires to be recognized as a light festival, but also diverges from the original models that have inspired its creation. This process of differentiation is also expressed by the manager of the ILO.

Describing his intention to organize an annual reunion of light festivals organizers in order to promote the circulation of best practices and mutual learning he clearly acknowledge the differences that exist among different light festivals:

"We are thinking of inviting every light festival (organisers) this year because …they (light festival organisers) are all the best in their own way, they're the best in their budget and they're the best in their city." (Interview, July, 2015) Specifically, he explicitly recognized that every organizer acts under specific local condition, producing a multiplicity of different light events that vary in duration, scale, design and objectives. The existence of such a broad range of formats and aspirations is also reflected in the wide range of reasons that motivated the process of "policy tourism" [START_REF] González | Bilbao and Barcelona 'in Motion'. How Urban Regeneration 'Models' Travel and Mutate in the Global Flows of Policy Tourism[END_REF] related to light festivals. As confirmed by the project manager of the ILO, motivations and scopes for studying existing light festivals and circulating the ideas and practices varies Crucially this process of emulation, reproduction and circulation of light festivals and installations contrasts with the idea of a shift toward forms of urban tourism based solely on creativity and embedded knowledge distinctively linked to the destination. Like urban policies [START_REF] Bunnell | Urban Pulse-A Geography of Serial Seduction: Urban Policy Transfer from Kuala Lumpur to Hyderabad[END_REF][START_REF] Mccann | Urban Policy Mobilities and Global Circuits of Knowledge: Towards a Research Agenda[END_REF]) and political-cultural objects [START_REF] Moser | Circulating visions of 'High Islam': The adoption of fantasy middle Eastern architecture in constructing Malaysian national identity[END_REF]Ong & du Cros, 2012a;[START_REF] Pow | Securing the "Civilized" Enclaves: Gated Communities and the Moral Geographies of Exclusion in (Post-)socialist Shanghai[END_REF], concepts and artefacts relating to light festivals have travelled widely and have led to the proliferation of expert-endorsed, public-funded and professionally-managed cultural events based on the attraction of light and illumination [START_REF] Hernandez | Comment l'illumination nocturne est devenue une politique urbaine : la circulation de modèles d'aménagement de Lyon (France) á Puebla, Morelia et San Luis Potosi[END_REF]. Thus, what we are seeing in light festival based tourism is a new form of conventional tourism, happening alongside more novel forms of tourism [START_REF] Richards | Creativity and tourism: The State of the Art[END_REF][START_REF] Richards | Creativity and Tourism in the City[END_REF]. Instead of a decline in staging and a rise of co-creation in tourism cities and their associated tourist experience, illumination practices and light festivals demonstrate the permanence of efforts and attempts at re-staging the tourist experience and in the construction (usually top-down, elite-centred) at tourism cities.

Urban tourism and tourism stagings

The use of light and illumination to stage a spectacular experience (Edensor, 2015a;[START_REF] Mallet | Exposer Les Espace Référents D'une Politique Urbaine : Le Cas de Mises en Lumière á Bordeaux[END_REF] should be seen in relation to a genealogy of staging and theming in tourism.

From conserved heritage sites to purpose-built cultural attractions, the process of staging plays an important role in touristic purposes [START_REF] Dicks | Culture on Display: the Production of Contemporary Visitability[END_REF][START_REF] Lukas | The Themed Space: Locating Culture, Nation and Self New York[END_REF]. While innovative or new forms of lighting are important for the staging of experiences at light festivals, other/older approaches deploying popular culture, traditional values or utopian visions can be found at work in tourism places around the world too. Such production and consumption of spectacular experiences often evoke discussions of reality versus fantasy. For example, [START_REF] Tucker | Welcome to Flintstones-Land: Contesting Place and Identity in Goreme, Central Turkey[END_REF] examined how Goreme's tourism entrepreneurs and residents deploy popular American cartoon 'The Flintstones' in the marketing and development of tourism in the central Turkish village. Branded 'Flintstones-land' because of its sublime natural caverns and chimneys, [START_REF] Tucker | Living with Tourism: Negotiating Identities in a Turkish Village[END_REF] argues that Goreme's tourism are practiced in a hypo-reality (or hyperfakality) where Goreme's natural and real geological features are experienced as more fake than fake. Rather than a shift towards relational forms of tourism, tourism experiences at light festivals are likely to centre on the aesthetical, artistic and 'hyperreal' [START_REF] Baudrillard | Simulacra and Simulation[END_REF][START_REF] Eco | Travels in Hyperreality New York[END_REF] qualities that new modes of lighting bring to the monuments, buildings, streets and cities.

As such, light festivals are likely to evoke forms of urban tourism that are beyond the current theorization of an on-going transition toward new forms of urban tourism where a growing "part of tourism deliberately avoids staged experiences in officially sanctioned tourist spaces" and " the passive consumerist notion of former urban tourism…is increasingly replaced by an active search for new and unusual personal experiences and for being part of the visited place and the lifestyle ascribed to it" (Fuller andMichel, 2014: 1306). According to this narrative urban tourism shows an increasing disenchantment toward the "staging" of many tourist destinations and locations and is instead characterized by a quest for more "ordinary" and "authentic" experiences of the city [START_REF] Maitland | Everyday life as a creative experience in cities[END_REF][START_REF] Richards | Creativity and tourism: The State of the Art[END_REF][START_REF] Richards | Creativity and Tourism in the City[END_REF]Richards and Wilson, 2007;[START_REF] Tan | A model of "creative experience" in creative tourism[END_REF] Yet [START_REF] Edensor | The Rich potentialities of Light Festivals[END_REF] remarks that critiques that focuses on the intensified commodification and theming of urban space fail to acknowledge that this events "are not necessarily experienced passively but are occasion for pleasure and fun" (pg. 87). In a similar vein, several studies [START_REF] Dicks | Culture on Display: the Production of Contemporary Visitability[END_REF][START_REF] Lukas | The Themed Space: Locating Culture, Nation and Self New York[END_REF] have revealed that visitors do not always see theming as an endeavour at creating the authentic. Instead, visitors often accept simulations so long they know these are based on partial-truths and that the simulations enrich their experiences. Crucially this resonate with the recent works on the enchanting and affective qualities that innovative forms of illumination possess [START_REF] Edensor | Illuminated Atmospheres: Anticipating and Reproducing the Flow of Affective Experience in Blackpool[END_REF][START_REF] Edensor | The Rich potentialities of Light Festivals[END_REF][START_REF] Edensor | The Gloomy City: Rethinking the Relationship between Light and Dark[END_REF]. For instance, the work of Edensor and Lorimer on the experience of Speed of Light, a performance event staged in Holyrood Park, during the 2012 Edinburgh International Festival reveals how the carefully choreographed staging of artificial light effects, producing a new experience of topography, terrain and atmosphere is able to generate enchanting effects that contain the power to "dramatizes the experience of looking, listening and feeling." (Edensor and Lorimer, 2015 p.1).

Illuminating sites, thus, can work towards a greater sense of navigation for visitors at night and a greater appreciation of the thematic elements of the city and its elementshighlighted and facilitated via the spectacle of calculated illumination. As acts and practices geared towards theming urban places and simulating fantasy-scapes, light festivals and their enchanting lighting schemes are appreciated and consumed for the ways in which they add to the experience of cities and urban areas. Consequently, the authentic presentation of buildings and sites are not always a concern to visitors.

Conclusion

The circulation and copy of policies from one city to another is by now a common practice that characterized an increasingly globalized world. Yet, in the field of tourism this strategy has hardly been considered effective. Conceptualized as a linear reproduction of external ideas and policies, this strategy of policy emulation has been accused to produce negative effects as the attempts to stage the tourism city has been often defined as counterproductive [START_REF] Smith | Space, Place and Placelessness in the Culturally Regenerated City[END_REF]Richard and Wilson, 2007). As a result, many authors have argued that urban tourism is experiencing a turn toward new forms of urban tourism characterised by a quest by visitors for 'typical' mundane experiences distinctively linked to the destination. Rather the adopting a similar approach, the paper has adopted a policy mobility perspective [START_REF] Mccann | Urban Policy Mobilities and Global Circuits of Knowledge: Towards a Research Agenda[END_REF] that approaches the circulation of policies as a socially constructed process, associated with increasingly intense forms of institutional layering and embedded power relations. This entails the analysis of how ideas, concepts and artefacts have circulated globally and the demonstration of how tourism policies are adapted and improvised from one city to in intricate and complex ways. The success experienced by all the light festivals around the world shows how forms of fast policy studied in Urban Studies and allied social science disciplines could also be successfully adopted in the field of tourism However, despite the increasing "local globalness" (McCann, 2011:120) that characterises the circulation of light festival at a global level, these events could hardly be described as related to bottom-up forms of tourism based on embedded knowledge or tourists' desire of authenticity driven by the will to "live like a local" (Richards, 2014:126).

Light festivals are often big-budget events, characterized by a strong top-down approach and endorsed by international networks and agreement and increasingly rely on the presence of internationally well-known artists [START_REF] Edensor | Blackpool Illuminations: Revaluing Local Cultural Production, Situated Creativity and Working-Class Values[END_REF].Specifically, the spread of light festivals around the globe offers a new insight on the process of development of urban tourism, revealing how that in spite of the recent accounts on the emergence of more relational form of tourism, elite-endorsed and often top-down attempts to re-stage the tourism city are still persistent. Rather than simply a move towards new forms of urban tourism characterized by a search for a stronger engagement with the everyday and mundane experience of the city, the diffusion of light festivals confirms the persistence of a wider range of tourism motivations in which under specific conditions, the simulation and the staging of the tourism experience are accepted and appreciated.

  related to light festivals to circulate. In 2013 the International Lightfestival Organization (ILO) was founded as an open platform that, according to the creator, aims to support light festival organization providing opportunities to collaboratively address curatorial challenges and delivers production solutions for outstanding light art projects. The association, that reunited 16 light festivals around the world, represents an arena where the organizers could share best practices about different issue related to the organization. Not only has the organization \ created an open-platform where organizers of light festival can share opinions,

  technical and artistic support to numerous festivals like Moscow, Riga and Rio de Janeiro. More recently, the technical team of the Fête des Lumières has started to act like a consultancy firm, having being hired to collaborate with the organization and development of light festivals and events all around the word. For instance, in 2014, the city of Lyon collaborated with the Emaar Group, a real-estate conglomerate in the Gulf, to create a light event in Dubai inspired by Lyon's Fête des Lumières. The resulting agreement saw the Lyon Light Festival team provide support to Dubai with artistic and technical know-how while the Director of the Lyon's festival took on the role of Artistic Director of the Dubai events. In exchange for the assistance, Dubai has become a financial partner in the Fête des Lumières. More recently, in 2016, the Lyon Light Festival team was hired by the city of Quito to organize the first edition of the Quito Light festivals as part of the United Nations Conference on Housing and Sustainable Urban Development. According to the Lyon Deputyin Charge of Culture, the international collaborations have generated 150 000 euros of revenue in 2013 -an amount that covered 7% of the next year events costs(La Tribune, 2014). Crucially, the combined action of these "scalar and network architectures"(Peck 2004: 399), has resulted in the creation of an increase of the number of light festivals. At the point of writing, almost 100 light festivals are active around the world, most of them developed in the last 5 years.Different cities, different light festivalsAnalysing the recent progressive development of the light festivals, two different trends have emerged. First, light festivals are becoming a global phenomenon. Originally light festivals were developed by European cities that, following the Lyon model, were trying to enhance their image and develop tourism. Nowadays, they're increasingly organized by cities in all continents. In the last 5 years new light festivals have emerged in South America,

  different kinds of event. Best practices and art installations continue to circulate among different light festivals at a global level. Instead, this process reflects the increasing "local globalness" (McCann, 2011:120) of policy circulation. Rather than a serial reproduction of a standardized format, ideas, practices and artefacts related to light festivals circulate globally and are recombined locally each time under specific local, cultural and economic conditions.

  broadly. While certain delegation are interested in understanding the entire process of development of such events and in develop collaboration, arguably with the intention of reproduce a similar format, others are instead exclusively interested in very specific areas such as crowd management or fund-rising. However, despite the fact that local culture and knowledge influence the development of light festivals, such a trend is hardly related to forms of tourism based on endogenous creative capital or on interactive experiences directly related to the everyday life of the location.Light festival creations are often characterized by a strong top-down approach. They are big budget events originating from the will of public authorities and private sector and endorsed by international networks and agreement. Often, they tend to adopt templates and installations that have circulated globally and may even have the tendency to deploy the same lighting installation in different festivals around the world (Schulter-Romer, 2013). For instance, the Cloud project have travelled from the Signal Festival in Prague(October 2013) to GLOW Eindhoven (November 2013) and later has been visible at the I Light Marina Bay light festival in Singapore (March 2014). Also, the project of the Dutch artists Collective Afterlight, that was permanently visible in the Molenstraat in Eindhoven since GLOW 2011, has been restaged in the festivals of Ghent, Jerusalem and Cascais.

Table 2

 2 Light festivals around the world (Source: compiled by authors, 2016) Year

Name of light festival, City, Country Lyon

  's success and international visibility play a key role in the progressive diffusion and the city quickly assumed a prototypical status. Numerous festivals explicitly cited the Fête des Lumières as a source of inspiration (for example, Osaka, Dubai), as a term of comparison (for example, Berlin, Amsterdam) or used lighting installations previously shown in Lyon (for example, Bejing, Osaka). Yet, not only has Lyon's success inspired other cities to develop new festivals of light, the French city has also actively contributed to the rise of new lighting events. In 2002 the city of Lyon created LUCI (Lighting Urban Community