J F Rysman

Y Lemaître

E Moreau
email: emoreau@novimet.com

ERAD 2012 -THE SEVENTH EUROPEAN CONFERENCE ON RADAR IN METEOROLOGY AND HYDROLOGY X band polarimetric & Doppler radar observations of heavy precipitation events over the Mediterranean region (France)

Introduction

Precipitations in the Mediterranean region are characterized by a high spatial and temporal variability. Indeed, because of its latitude (between 36° and 44° N) the Mediterranean region is affected both by sub-tropical storms and mid-latitude synoptic disturbances. Summer is warm and dry while being persistently affected by the Azores anticyclone and winter is temperate and moderately humid because of the mid-latitude westerlies. Moreover since the Mediterranean region is surrounded by mountain barriers and strong contrasts between sea and continent exist, local forcings are also important. In this context the HyMeX (HYdrological cycle in the Mediterranean EXperiment) experiment has been launched in order to better understand and quantify the hydrological cycle and related processes of this Mediterranean region. Particular emphasis is given to high-impact weather events, inter-annual to decadal variability of the Mediterranean coupled system and associated trends in the context of global change. This campaign extends from 2010 to 2020 with special intensive observing periods (SOP) involving a lot of dedicated instruments. The first SOP will begin the 5th September 2012 and will last until the 6th of November 2012. LATMOS participation, related to high precipitation events, will be done by mean of an X band polarimetric & Doppler weather Radar called HYDRIX based close to Nice in the North East of the French Mediterranean coast. This radar, owned by the LATMOS/CNRS, developed and operated by NOVIMET, collects in an operational way since 2008 reflectivity, Doppler and polarimetric data with a time step of 5 minutes and a mean spatial resolution of 1 km.

The present work is devoted to the temporal and spatial characterization of the precipitation that affects the Provencal and Ligurian regions. A statistical and a spectral analysis are performed in order to establish a climatology of rain events and to determine main variability and tendency of the regional rainfall. In the following some technical information upon the HYDRIX radar and the used dataset are given in section 2 and 3. The fourth section is dedicated to the main methods used in this study to analyze the dataset. The fifth section discusses results and the conclusions are given in the last section.

Instrument

The X band, polarimetric and Doppler radar HYDRIX is based on Mont Vial (~ 1500 m) close to Nice in the south-eastern part of France. Main specifications are summarized in table 1. This radar is particularly efficient in mountainous region thanks to its frequency of operation and its offset feed, which reduce ground clutters. Moreover it has a reduced size (antenna diameter ~ 1.5m) and no radome. More technical information can be found in Lebouar et al. 2008 and[START_REF] Moreau | Rainfall spatial variability observed by X-band weather radar and its implication for the accuracy of rainfall estimates[END_REF] The conversion of radar reflectivity to rainfall intensity is done by the ZPHI algorithm [START_REF] Testud | The rain profiling algorithm applied to polarimetric weather radar[END_REF]. This algorithm corrects the beam attenuation along the path, and computes a N 0 * parameter (derived from the drop size distribution N(d)) in order to retrieve the rain rate through the relation:

b b Z aN = R - * 1 0
An estimation of rain at ground is done using a weighted average of rainfall obtained at multiple elevations. Weights are computed base on a quality index which takes into account the altitude of measurement, water phase and beam masking. For much detailed description about those methods see [START_REF] Testud | The rain profiling algorithm applied to polarimetric weather radar[END_REF] and [START_REF] Moreau | Rainfall spatial variability observed by X-band weather radar and its implication for the accuracy of rainfall estimates[END_REF].

Rainfall data validation has been performed by comparison with S band radar (Diss et al. 2009) and rain gage (Moreau et al. 2009) observations

Dataset

The radar provides several real time quantities: instantaneous rainfall, cumulated rain, rain displacement, reflectivity and hydrometeor classification. It also provides Doppler information in rainy regions and in clear air regions close to the radar. The dataset gathers observation since March 2009 until now with nearly no interruption. The data range is 150 km with a spatial resolution of 1 km² and a temporal resolution of 5 minutes. However despite the correction of radar attenuation along the beam path, precision on rainfall estimation decreases with distance from the transmitter. Thus, for precise quantifications, we restricted our study to measurements realized at less than 60 km from the radar. All these quantities will be used to document the low level environment and the internal dynamics of rain events, their microphysics and the interactionmechanisms leading to high-accumulated surface rainfall.

The region is particularly attractive because it covers a great number of different types of basin, topography and soil. Hence this area is divided in 6 regions (see figure 1): a high mountain region (Alpes), 2 flatland regions (Pô and Provence), a foothill region (Pré-Alpes), a coastal region (Côte) and the Mediterranean Sea (Méditerannée). Such a dataset with a wide range, spatially and temporally speaking, is highly valuable to study and analyze rain processes.

. Methods

For characterized rainfall and better understand its variability, various statistical methods were applied to the dataset including Fourier and wavelet transform, probability distribution function (pdf) and correlation. Some technical points are summarized in this section.

Wavelet analysis

To detect large scale temporal oscillations, we realized a wavelet analysis. Since Morlet had mathematically formalized it in 1984, wavelet analysis has been applied successfully in various fields (medicine, economy, meteorology). Indeed wavelets are a powerful tool to detect and analyze intermittent oscillating signals in time series.

By definition, a wavelet function satisfies two conditions:

-the admissibility condition

0 ) ( = ∫ +∞ ∞ - dt t ψ
with ψ the wavelet function called mother wavelet, which insures that the wavelet has a wave-like structure. This condition is very important to detect oscillations in the signal.

-the compact support condition

1 ² ) ( = ∫ +∞ ∞ - dt t ψ
which insures that the wavelet has a fast-decay . This condition helps us to localize the oscillations in the time series. Wavelet function can be dilated (or contracted) and translated trough the transformation:

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - = a b t a t b a ψ ϕ 1 ) ( ,
where φ is a daughter wavelet, a the scaling coefficient and b the translation coefficient. Wavelet transform is then realize on a given f(t) function with this operation :

dt a b t t f a t t f b a C ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - = ∫ ∞ + ∞ - ψ ψ ) ( 1 )) ( ), ( , , (
where C are the wavelet coefficients. For our analysis we used the Morlet wavelet function that is widely used in geophysics because its shape permits to easily detect oscillations:

2 / ² 2 / ² 4 / 1 ) ( ) ( t t i e e e t - - - - = ε ε π ψ
where ϵ is a non-dimensional number assumed to be equal to 5 in order to satisfy the admissibility condition.

Scaling

The atmosphere is a complex system where various processes with various spatial and temporal scales happen together. However this system has some statistical properties known as scaling or self-similarity that can link the different scales by only the scale ratio and a single parameter. First steps of the theory have been developed by Kolmogorov (1941) for velocity increments. He showed that power spectral density S of velocity increments follow the form (in isotropic atmosphere assumption):

3 / 5 3 / 2 ) ( - ∝ υ ε υ

S

where υ is the frequency and ϵ is the kinetic energy dissipation rate.

Within a turbulent energy flow, transfer from large scales to fine scales can be seen as decreasing size eddies which separated always in the same way until dissipation scale. Despite atmosphere isn't isotropic and homogeneous and that the Kolmogorov relation has been defined in a spatial framework, lot of studies have shown that this behavior is found in most of geophysical fields (e.g. Gage 1986 (wind and temperature), Tessier 1993(clouds radiance) or Verrier 2011(rain)). We tried to verify the existence of such symmetries in our rain measurements.

Results

Statistical validation

As explained previously, rainfall products have been validated in term of instantaneous value in the past. These products are presently evaluated in a statistical sense based on the scaling properties of rainfall (c.f. subsection 4.2). A Fourier transform is applied on the dataset and power spectral slopes and scaling breaks position are evaluated through comparison with previous studies. Within the 60 km range around the radar, 5 km² areas are selected, their rain power spectra are calculated and averaged.

To estimate the slopes of the spectra, linear regressions are realized on a log-log representation of the spectra (see figure 2). The slopes are found to be 1.81 for periodicity lower than 2 hours, 1.5 between 2 hours and 1 day, 0.73 between 1 day and about 10 days and about zero higher. Those results, including the position of the breaks and the slopes are shown to be in good agreement with previous studies (e.g. [START_REF] Fraedrich | Scaling regimes of composite rainfall time series[END_REF]. We can notice peaks related to the diurnal cycle (one day), the annual cycle and a peak at 15 minutes, which results from a change in the pulse repetition frequency of the radar (every 15 minutes) during test phases. Despite the spectral power displays the full range of scales of rainfall, it is restricted to the second moments (variance). In order to analyze every order of moments, the probability distribution function can be analyzed. Indeed the n order moments are directly related to this function (see Schertzer 2002 for precisions). Therefore, the shape of the function is an important indicator to validate the dataset. Results are given in figure 3 for each region indicated on figure 1. The pdfs of the different regions appear rather similar to each other except for the Pô region, which underestimates low rain rate and overestimate high rain rate. These biases result certainly from the effect of the mountain that masks over the plains of Pô low elevated precipitation events. These pdfs are lower in probability than the climatologic data corresponding to the north Mediterranean region and used by the ITU (International Telecommunication Union). It is probably related to different temporal resolutions (1 min for ITU) and to the fact that the region cover by the ITU covers the all North Mediterranean region. Moreover some rains events can be missed by the radar because of mask or beam attenuation. Nevertheless shapes are in good agreement (except for the Pô region).

Temporal variability

The rainfall behavior in the region and main processes that control precipitation can be first studied in analyzing the main cycles in the rainfall. Figure 4 gives the diurnal cycle of the rain rate for the various geographical regions. Strong contrasts between the different regions can be seen. Especially, the Mediterranean and the coast keep a rather constant rainfall rate during the day whereas land regions experiment a strong diurnal cycle link to the convection in the afternoon. Seasonal variations are also important (not shown) with no diurnal cycle between October and March. During this period, rainfall is maximal on the coast and the Mediterranean. Between April and September, the average rate is maximal during the afternoon on land region and very low on the Mediterranean. Those results put in evidence that the main weather regimes are stratiform in winter and convective in summer.

Figure 4 Annual Mean of average rain rate on various domains, function of the time of the day (mm/(h.km²)) Figure 5 Wavelet coefficients for rainfall between 2009 and 2011 Figure 3 Probability distribution function of the rain rate (mm/h) for various domains and for climatologic data used by ITU (International Telecommunication Union) corresponding to Mediterranean region

As explained previously, another way to explore cycle is the wavelet analysis. This tool is presently used to detect large scale and intermittent signals impacting the region. Results given in figure 5 reveal significant signatures with a 40-50 days periodicity. This mode impacts fundamentally the rainfall in the region but doesn't seem to be related to any seasonal cycle. Other studies (on wind and pressure fields) showed similar periodicity in the Mediterranean region [START_REF] Gomis | Low frequency Mediterranean sea level variability: The contribution of atmospheric pressure and wind[END_REF] for instance).

In conclusion, important and variable diurnal cycles are observed in the region depending on the season and the geographical location. A large scale oscillation which influences strongly the local precipitation is also clearly detected in the rainfall.

Extreme events localization

In this section the spatial variability of extreme events is investigated statistically. As previously the pdf is computed on 5 km² area in the radar domain and the value for which rain rate is exceeded for 0.01% of the whole time series is got. 6 for all the year. They highlight regions statistically prone to extreme rainfall events. It reveals that foothills and concave regions have a higher probability to be subjected to heavy precipitation than high mountain or sea. Summer months are also (not shown) prone to heavy events because of deep convection. Such results highlight the high impact of local forcing on rainfall in this region. They could be used to choose regions were mobile stations can be deployed (area were the probability of extreme events is higher).

Relationship between rainfall and altitude

Previous subsection showed that extreme rainfall events are highly space dependent. On this context which role has the relief on rainfall events ? Figure 7 gives the rain intensity in function of the ground altitude. It shows that altitude and rain rate is positively correlated until about 1200 m. Higher such a relation doesn't exist anymore. This result can be explained by rainfall that is essentially generated by orography. We can also notice 2 regimes of correlation, which could be related to different orientation of slope versus the main moisture flux that led to rain.

Relationship between rain displacement and rain rate

In previous subsections, we showed how rainfall is dependent on geographical characteristics of the region and time periods. In this last section, we investigated the link between rain rate and rain displacement that is coarsely connected to the local atmosphere dynamics. Results presented in figure 8 show that the most probable direction of displacement of rain events is from south-west to north-east. It is also in this direction that the daily mean rain rate is the higher. If we assume that, in average, the rain displacement is with and along the wind, this result can be explained because of the humidification by the Mediterranean Sea of the lowest layers feeding convective motions. The Mediterranean Sea appears thus as a key factor in rainfall events over the region covered by the radar.

Conclusion and Outlook

A 3-year rainfall time series obtained from the X band, polarimetric and Doppler radar HYDRIX is analyzed to investigate the spatio-temporal variability of rain events over the southeastern coast of France. The spatial resolution is 1 km and the temporal resolution is 5 minutes. Statistic tools such as Fourier and wavelet spectra and probability distribution functions are used for this purpose. The results show a strong spatial and temporal variability of rainfall over this region. Diurnal cycle exists only on land and high scale oscillations (40-50 days) strongly affect the area. Regions prone to heavy precipitation events are mainly foothills. Intense rain events come mainly from the southwest and results from flux bringing humidity from the Mediterranean Sea that rise over elevated foothills. Strong rain accumulation corresponds to altitude up to 1200 m.

Complementary statistical analyses such as principal component analysis are presently realized on ECMWF reanalyzes in order to know the main dynamical modes, which impact the region and are related to the present rain variability. Case studies of the dynamical and microphysical characteristics of extreme events sampled during this period (selected on the basis on the main findings of this work) will be also done. The database will be extended until 2013.

Figure 1

 1 Figure1On the map is shown regions that were studied in different analysis.

Figure 2

 2 Figure 2 Power spectra for rainfall between 2009 and 2011. Lines highlight the 4 scaling regimes.

Figure 6

 6 Figure 6 Rain rate (mm/h) exceeded for 0.01% of a yearResults are given Figure6for all the year. They highlight regions statistically prone to extreme rainfall events. It reveals that foothills and concave regions have a higher probability to be subjected to heavy precipitation than high mountain or sea. Summer months are also (not shown) prone to heavy events because of deep convection. Such results highlight the high impact of local forcing on rainfall in this region. They could be used to choose regions were mobile stations can be deployed (area were the probability of extreme events is higher).

Figure 7

 7 Figure 7 Point density of height versus rain accumulation.Colors are logarithmically spaced.

Figure 8

 8 Figure 8 Point density of rain displacement angle versus rain accumulation. O° is pointing to the North, 90° to the East. Colors are logarithmically spaced.

  .

	Frequency	9375 MHz
	Wavelength	3.2 cm
	Antenna	1.5 m (offset feed)
	Antenna gain	41dBZ
	Scan velocity	14 deg./s in azimuth
	Beam width	1.5 deg
	Pulse length	0.5 to 2 µs
	Pulse repetition frequency	1000 Hz and 500 Hz
	Sensitivity	0 dBZ at 55 km or 100 km
	Polarization mode	Simultaneous H and V
	Table 1 Hydrix capabilities.


'It's a question of prestige': Climate change as public policy in Turkey

Climate change has been a preoccupation of public bodies in Turkey since the country signed the UNFCC in 2004. Before then, periodic environmental policies were enacted, but under the remit of each Cabinet ministry and without handing over central control of the Ministry of the Environment. Furthermore, no action-oriented policies on climate change were developed. The issue came to public prominence relatively recently in Turkey, but interest in the issues at state is growing.

Climate Change (CC) has fallen within the auspices of the Ministry of Environment and Urban Planning since 2010. The structure of the ministry has been modified and the ministerial staff and premises have been increased in size. In addition, despite being previously affiliated with the Meteorology Department, which specialized exclusively in weather forecasts, CC policies have become progressively detached from it. In July 2010, a new department focusing on CC was founded, with its own staff. Questions were then asked concerning the reasons for the rapid evolution within the ministry. Why had CC become one of the priorities of the ministry and why had it become a field in which both international cooperation and project-management activities had been given a renewed focus? These questions give rise to another set of questions on environmental policies in Turkey: When and for what reasons has there been genuine change? Why have public bodies felt the need and necessity to restructure environmental policy and make CC a central focus?

This article aims to analyze the place of institutions and the international context concerning CC policies up to 2010 in order to offer a better understanding of their role in the development of environmental policies in Turkey. This analysis will also adopt a local point of view with respect to the desertification of the Konya Plain. The latter is particularly important, given that as one of the most negatively affected regions by both CC in Turkey and public policy, it provides a good example of the key elements of the general political orientation of the CC issue in Turkey as a whole. International institutions have been at the forefront of the framework of environmental policies, which is due to the fact that they symbolized a renewal in public action modalities. They also allow a more international and

negotiated definition of the environment as a public problem. An analysis of the relevant policies reveals international institutions have been the driving force in the emergence of CC as a public policy in Turkey. It is also clear that their commitment to such policies forces governments to take action in order to raise their prestige at the international level. *** PULLOUT International institutions have been at the forefront of the framework of environmental policies *** The environment as political object: From instrumentalization to preservation Until the mid-1990s, environmental policies were not a priority for Turkish governments, which were mainly concerned with economic politics. Similarly to other areas, policies governing environmental issues depended on the beliefs of policymakers, which were determined on the basis of a series of prescribed and hierarchical requirements identifiable in society. [START_REF] Gartaud | Politiques Nationales: Élaboration de l'Agenda[END_REF] An incontestable commitment to fast and continual economic growth was at the heart of social tensions in the country at the time, not only because of its destabilizing effects but also due to the fact that instead of taking action to bring about political reform, decisionmakers considered economic growth to be a remedy to social problems. [START_REF]A typical example is the Southeast Anatolia Project (GAP), a giant development project in the agricultural sector consisting of the construction of a number of hydropower dams and hydroelectric power plants[END_REF] In this way, the environmental degradation caused by the over-exploitation of natural resources and waste disposal, which went far beyond the ecosystem's capacity for recovery, increased drastically, especially after the 1980s. [START_REF] Fikret Adaman | Environmentalism in Turkey. Between Democracy and Development[END_REF] A wide range of activities --uncontrolled industrialization and urbanization, the intensive use of chemical products and pesticides in agriculture, mismanaged touristic activities and large-scale irrigation and energy projects --which were undertaken without taking environmental dynamics into account, resulted in considerable damage to the ecological system in Turkey. 4 *** PULLOUT Turkey long neglected environmental issues and treated the natural world as simply a resource for exploitation *** By focusing on economic development, Turkey long neglected environmental issues and treated the natural world as simply a resource for exploitation. Hence, Turkey did not develop a political program of environmental protection until the 2000s, despite numerous pressing ecological issues, such as the nuclear explosion at Chernobyl in 1987.

It is fair to say that overall there has been only sporadic implementation of environmental policies during the past three decades. However, such practices were not outside the law; a brief study of Turkish legal history reveals the existence of a substantial body of legislation on the matter, with environmental rights and duties shared between the central government and local bodies. 5 However, this legislation was often ignored, and legal bodies often failed to enforce sanctions concerning industrial pollution, waste disposal, deforestation and the exploitation of water resources. Moreover, there was no effective international pressure to push the government to pass proper legislation on the matter.

A rapid increase in environmental problems and rising international pressure on the matter have pushed the government to take proper measures to pass laws, decrees and regulations for the protection of the environment, in additions to norms on air and water quality. Thanks to the support and encouragement of international organizations, the government has finally begun --modestly, so far --to introduce institutional and legal changes governing the management of the environment.

A brief comparison between European countries and Turkey reveals that environmental concerns only gained public prominence very recently in the latter. While the emergence of ecological movements and parties can be dated to the late 1970s in Europe, in Turkey, the first green party was founded in 2002, after a precursor party was shut down in 1994.

***

PULLOUT

The first institutional attempt by the Turkish government to respond to environmental concerns dates back to 1978 *** Chronologically, the first institutional attempt by the Turkish government to respond to environmental concerns dates back to 1978, when an undersecretary for the environment at the Prime Ministry was created in order to coordinate various activities concerning the environment. The first law on the environment was written in 1983 by this body. This environmental body grew in importance, becoming a separate Ministry of the Environment in 1991. 6 In 2004, the Ministry of the Environment was merged with the Forestry Ministry, 7 principally as a response to EU calls for improvement in the coordination of environmental policies. Needless to say, bodies such as the Ministry of Energy and Natural Resources, the Ministry of Tourism and the Ministry of Health also have to deal with environmental questions within their areas of responsibility. Since 2004, Turkey's Ministry of the Environment --and more recently the Ministry of Environment and Urbanization --has been considered the focal point in the country concerning environmental issues by the EU and the United Nations. In addition, municipalities and administrative bodies of the central government in all 81 provinces are charged with the implementation of environmental policies at the local level. 8 This well-defined organizational structure is also enshrined in the Constitution, which sets out a series of articles on the rights and obligations of the state and citizens to protect the environment. 9

In spite of the allegedly "perfect" task division between local and national institutions, the operation of public institutions remains determined by the central government. As a local administrator noted: "Local policies are not elaborated independently from national ones. It's particularly difficult especially when it comes to questions concerning a large portion of the population. The main function of local entities is to execute policies made at the national level in the shortest time period." 10 The most symbolic example of this is the implementation of the action plan for the Konya Plain (the Konya Plain Project), designed to fight against drought and desertification. Public entities, academic staff at a local university, associations and local enterprises and business organizations came together to design solutions to facilitate the irrigation of cultivated soil in the plain, which was under an increasing threat of drought. In 2010, a local official in Konya stated: "We have been working on the Konya Plain Project for years. A number of associations and organizations including the Chamber of Commerce, researchers from the University of Selçuk, the provincial governorate and so on have come together in order to design this plan. Yet, we're still waiting for the finances. We were told that the plan would be merged with the current national plan of economic planning but we have now realized that this is not the case. The plan has been submitted for the approval of the State Planning Organization (DPT). Although the situation of agriculture [in the plain] is alarming, the priorities of Ankara and Konya [province] do not always coincide." [START_REF]official from the Ministry of Food, Agriculture and Livestock[END_REF] In addition, the divergent priorities of economic development at the local and national level give way to contradictory tendencies. In Konya, for example, although the region is suffering from a progressively worsening dry climate, sugar beet --which requires intensive irrigation --is still subsidized, even though there are other agricultural products that might better adapt to the region's climatic conditions. This choice is justified by the existence of an advanced sugar industry in the region.

***

PULLOUT

The centralization of public policy has usually constituted an obstacle to the flexible implementation of environmental policies ***

The centralization of public policy has usually constituted an obstacle to the flexible implementation of environmental policies. In spite of the existing legislation on the matter, there has been limited implementation because local actors have limited powers, having been deprived of sufficient means to allow them to take proper action. The institutional weaknesses of environmental bodies has gone hand in hand with the fact that the government has tended to hide its failure to monitor violations and impose effective sanctions where necessary. [START_REF] Aydın | The State, the Civil Society, and Environmentalism" in Adaman and Arsel[END_REF] Nevertheless, there is a mismatch between attempts to integrate environmental concerns into development plans and the country's institutional inefficiency and complacent attitudes about monitoring and implementation. Although the government has been very active in the introduction of laws on the environment, the lack of funding and staff has jeopardized their effectiveness. In 2010, we observed that more than half of the staff of the Ministry of Environment and Forestry was composed of engineers, with a near total absence of sociologists and economists. Hence, public works were almost entirely technical in nature and did not take into account human and social dimensions.

The way in which environmental questions were treated in Turkey during the 1990s is illustrated by the fact that no specific attention was paid to the works and recommendations of the World Commission on Environment and Development (the Brundtland Commission of 1987). This was the first serious attempt to show that environmental problems were strictly related to specific forms of development. Yet, before 1989, environmental concerns were treated as being separate from questions of development. Furthermore, the recommendations of the Rio Earth Summit [START_REF]The United Nations Conference on Environment and Development (UNCED), also known as the Rio Summit[END_REF] (the Convention on Biological Diversity [CBD], the United Nations Framework Convention on Climate Change [UNFCCC], the summit's declaration and Agenda 21) had little effect on changing the relative priorities of development and the environment in Turkey. The sole exception was about water, and the recommendations made in Agenda 21 were used as the basis of development projects.

Taking into account the theories of the environment elaborated by Jacques Theys, one could argue that the issue of the environment in Turkey is one aspect of a nexus of relationships between the human and the natural environments, qualified and even quantified in terms of economic utility until the mid-1990s. [START_REF] Theys | L'environnement à la recherche d'une définition[END_REF] Theys's theory considers the environment in all its forms but it restricts the field to areas used by and for humans. [START_REF] Larrue | Analyser les politiques publiques d'environnement[END_REF] Influenced by the increase in international concerns about "sustainable development" since the second half of the 1990s, both NGOs and the Turkish government began to link environmental issues with development. A utilitarian conception of the environment has gradually been replaced (albeit quite minimally) by a conception focusing on human-nature relations. In other words, it determines what is acceptable in nature for human beings and vice versa. It defines the environment "as a nexus of problems, risks and dysfunctions of which perception varies in time and space, and as a public and private sphere of action." 16 Therefore, focusing merely on the immediate effects of human activities on the environment appears less likely, since such activities might have further noteworthy consequences. [START_REF] Rumpala | Régulation publique et environnement[END_REF] As a signatory of a number of international protocols and agreements on the protection of the environment, Turkey has demonstrated its commitment to partnership with NGOs in the field of development. The national program on the environment and development issued for the World Summit on Sustainable Development in Johannesburg in 2002 is a good example. Turkey asked a number of civil society organizations and academics to help prepare for the event. This was the first systematic attempt to establish an institutional relationship between the approach to the environment and development in Turkey.

Turkish legislation on the environment comprises 20 laws, 27 international conventions and agreements and 15 decrees, all concerning various spheres of the environment. 18 This legal framework changes rapidly and the laws, agreements and decrees could well have increased since the publication of this paper. Furthermore, one should pay attention to a particular situation concerning the practice of this legislation: While more than half of the laws and 11 of the conventions and decrees were promulgated after 2002, the rest took more than 25 years to be adopted. Turkey took five years to ratify the UNFCCC and the Kyoto Protocol.

What changed with regard to the Turkish government's approach to the environment that it decided to sign up to such agreements? Apart from tragedies such as the explosion of an oil tanker in the Bosporus Strait in 1994, [START_REF]Two ships --M/T Nassia and M/V Shipbroker --collided in the Bosporus, causing the death of 29 people. A total of 15,000[END_REF] Turkey has not experienced dramatic ecological catastrophes, excluding some prolonged but local droughts. There are two main reasons for the change: On the one hand, Turkey has progressively grown aware of the local effects of CC, thanks to studies led by a number of public institutions, especially the National Institute of Meteorology, on pluvial flooding and desertification tendencies. [START_REF] Lelandais | Gestion Publique du Changement Climatique et la Désertification de la Plaine de Konya en Turquie[END_REF] On the other hand, given the country's progress toward integration with EU norms, Turkey has adopted a strategy of taking part in international negotiations on the environment in order to increase its prestige and to find foreign funding for environmental projects necessitating financial support. Initially, the latter reason helped the establishment of public policies concerning CC; then, it contributed to a consolidation in the fight against CC --namely, the implementation of a genuine public environmental policy.

The role of international public policy transfers in Turkey

The first studies on policy transfers [START_REF]A number of researchers have put "policy transfers" at the core of their efforts. Among the most significant[END_REF] were launched in the US in the 1960s to arrive at a better understanding of local public policies. Research at the international level led to the identification of the factors that determined the rhythm and extent of the transmission of an innovation within a nexus of organizational and institutional units that are supposed to adopt it. [START_REF] Delpeuch | L'analyse des transferts internationaux de politiques publiques: un état de l'art[END_REF] Policy transfer studies offer a better understanding of how and why some problems come to the public policy agenda in a country. These studies might also offer a proper basis for an understanding of environmental policy in Turkey. In particular, the theory of new institutionalism makes available a set of analytical tools that allow an understanding of Turkey's decision to focus on the environment and CC as a means of increasing its prestige.

***

PULLOUT

Two main orientations in Turkish foreign policy were decisive in the arrival of climate change as part of public policy ***

Two main orientations in Turkish foreign policy were decisive factors in the arrival of CC as a part of public policy. The first was the arrival of the Justice and Development Party (AK Party), a conservative party, to power. The AK Party's foreign policy has been shaped by the ideas of former Foreign Minister and current Prime Minister Ahmet Davutoğlu. In his book "Strategic Depth," Davutoğlu underlines the necessity of solving problems with its neighbors and simultaneously accelerating the negotiation process with the EU if Turkey is to become a regional power. [START_REF] Davutoğlu | Stratejik Derinli: Türkiye'nin Uluslararası Konumu[END_REF] In accordance with this objective, Turkey has to improve its image at the international level and to prove cooperative in the settlement of global problems such as the environment.

The second orientation is the gradual harmonization with the EU of all public policies. By 2010, senior officials at the Foreign Ministry thought that the country needed to focus on "the improvement of international prestige of the country. This depended on the ratification of international agreements that were recommended by Western countries and concerned many areas, including related to the human and environmental rights." [START_REF] Interview | Turkish diplomat[END_REF] On the basis of these two orientations, the key to understanding Turkey's decision to promote action against CC is, as the new institutionalists point out, to see that it involves the adoption of a set of solutions that are fashionable in the international arena more than a rational choice. From this point of view, policy transfers are considered less a part of scientifically elaborated strategies through which political actors seek to increase their efficiency and effectiveness than the expression of a need for legitimation: By participating in CC agreements, Turkey seeks to demonstrate that the country is acting properly to achieve a goal socially valorized. Consequently, Turkey seeks to show its confidence in and support for the actors that will carry out environmental activities. [START_REF] Meyer | Institutionalized Organizations: Formal Structure as Myth and Ceremony[END_REF] This strategy of involvement seems to be effective given that as Turkey becomes more involved in international CC agreements, more projects and new funding prospects also materialize. For example, Turkey is worried about desertification and, therefore, has taken part from 1992 onwards in negotiations on the preparation of the UN Convention to Combat Desertification (UNCCD). Turkey has been one of its signatory countries since 1994.

Turkey worked toward changing its status within the UNFCCC during the COP-7 Conference held in Marrakesh in 2001. Although not agreeing to Annex 2, Turkey supported Annex 1 and its particular conditions were accepted. 26 Turkey signed and promulgated the UNFCCC with parliamentary approval in May 2004. This strategy --which consists, first of all, of negotiating its status within the convention and making ratification dependent on the success of the negotiations --makes it clear that Turkey considers CC to be an external constraint but also a strategic resource. Turkey started a policy of trying to adhere to the formal elements of an agreement in order to preserve or improve its reputation in an area in which it is involved, while making arrangements appropriate to Turkey's situation, interests and specific needs, all beneath a veneer of compliance. [START_REF] Friedland | Bringing Society Back In: Symbols, Practices, and Institutional Contradiction[END_REF] A ministry bureaucrat specializing in questions relating to CC has stated: "Even if Turkey is formally included on the list of developed countries [in Annex I], this is not very credible, given the country's own social and economic indicators. On the basis of the country's individual role in CO2 emission, Turkey is a developing country. It may remain on the list, but [Turkey] cannot be expected to follow the same involvement criteria as OECD countries." [START_REF] Interview | bureaucrat from the Ministry of Environment[END_REF] This desire to be included in the list of OECD countries without respecting the implied involvement matches Turkey's foreign policy, which comprises a desire to be considered among European countries. This emphasis on European identity, which is illustrated by membership of many Western organizations --such as the European Council and the Organization for Security and Co-operation in Europe (OSCE) and NATO --might be linked to Turkey's international negotiations over CC.

In order to manage these multi-dimensional interactions, a council for the coordination of Turkey's CC activities has been set up, intended to centralize environmental policies and determine a "focal point" that will assume, through the relevant ministry, the main responsibility of leading all agreements and negotiations on the environment between Turkey and the relevant international organizations. 29 Also in 2004, a project was launched to support the preparation of the first national communication of Turkey about CC thanks to financing from the United Nations Development Programme (UNDP). The communication was made public in January 2007. Afterwards, Turkey drafted a document detailing its CC strategy, which was co-financed by the UNDP and the Embassy of the United Kingdom in Ankara. The document was published in December 2009.

Turkey's EU candidacy and pressure from European institutions led Turkey to deepen its involvement with regard to CC, 30 with a notable development being the ratification of the Kyoto Protocol in February 2009. Signing the Kyoto Protocol was a part of a strategy to obtain national prestige, as a bureaucrat of the Ministry of Environment stated: "Many countries were surprised when Turkey signed Kyoto. An ambassador of a non-signatory country invited the Environment Ministry to give its reasons. They even asked us why Turkey had changed its position on the agreement overnight. […] We underlined that given the changing conditions of the world and as a candidate for the EU, Turkey was convinced of the necessity of being involved in the Kyoto Protocol." 31 *** PULLOUT Turkey needs the support of international institutions to realize its projects and put environmental policies in practice *** Finally, Turkey needs the support of international institutions to realize its projects and put environmental policies in practice. Domestic financing is not enough for the realization of action plans. Demonstrating the country's engagement with respect to rules, ideas and practices allows Turkey to raise its prestige --particularly with the EU and the UN --and offers a range of advantages: It is easier to legitimize its activity when the country seems to have respect for principles based on consensus, rather than demonstrating the effectiveness of each action. Through this approach, Turkey increases its appeal to investors, highly qualified workers and customers. Turkey, according to this strategy, enhances its chances of obtaining certificates, quality labels, relevant authorization and the other benefits and, finally, enjoys a better reputation. 32 International-funding based projects are not limited to the implementation of national policies. There are also many local projects that rely on foreign funding. Most of these projects were started after Turkey signed the UNFCCC. Such involvement has allowed Turkey to prioritize projects long suspended because of a lack of funding, such as the case of the Konya Plain Project. Many projects and programs have been launched at the local level. Countries like Spain, the Netherlands and Japan have also contributed to this. Japan's funding is predominantly devoted to projects targeting the Konya and Seyhan Plains, supporting better use of water and the fight against drought in agriculture. The Netherlands is financing the protection project of Salt Lake and water-saving in the Konya Plain. These projects are under the supervision of the Environment Ministry and involve the participation of NGOs such as the World Wide Fund for Nature (WWF) and the Turkish Foundation for Combating Soil Erosion, for Reforestation and the Protection of Natural Habitats (TEMA). Agro-alimentary enterprises such as the company Eti and Coca Cola also finance these projects. Eti, TEMA and the WWF are focused on water use in agriculture and the education of farmers about rentable and effective irrigation techniques. [START_REF]The DESIRE project, the CORIN project and the ICCAP project are distinguished by their 34 Common interview with REC staff[END_REF] The Regional Environment Center for Central and Eastern Europe (REC), an international NGO based in Hungary, came to Ankara in 2005 in order to lead capacity-building activities aimed at public institutions and enterprises. All these activities have been implemented thanks to sources provided by the UN. An official at the REC involved in the project defines the objective of the organization as "strengthening the capacity of Turkey in environmental concerns in legal, technical, institutional and financial terms and thus accelerating the process of effective implementation of the acquis communautaire." 34 The Environment Ministry and the Ministry of Agriculture and Rural Affairs also lead public projects. This included policies aimed at promoting village-based agricultural production, which supports farmers' self-sufficiency. There are also credit cooperation and finance programs targeting irrigation micro-projects by drip-irrigation or aspersion techniques, or transition to organic agriculture. Similarly, species resistant to droughts in agriculture and in forests specific to each region have been specified and these species are used in reforestation activities. 35

The role of Europe

The convergence of public policies in a European orientation has been the main factor in the rapid evolution of some sectors. Claudio Radaelli defines Europeanization as "a process of construction, diffusion and institutionalization of formal and informal rules, procedures, paradigms, styles, action recipes, as well as of norms and beliefs. All of these were, first of all, defined and consolidated during the fabrication of European policies. Afterwards, they were incorporated in the logic of discourse, identities, political structures and public policies at the domestic level." [START_REF] Radaelli | The Europeanization of Public Policy[END_REF] In the case of Turkey, the UN provided financial support for adaptation and mitigation CC projects in Turkey, but Europe also played a key role in the implementation of a legal framework by exercising pressure on the country; the substantial reforms made to the national framework are mainly due to the introduction of European policies. This implies a change in the practices of domestic actors. [START_REF] Saurugger | L'Européanisation comme processus de transfert de politique publique[END_REF] In fact, all environmental laws promulgated by the Turkish Parliament result from the convergence with EU norms that was brought about with the objective of achieving common legislation at the European level. The declaration of the European Principles for the Environment (EPE) states that these principles "consist of the guiding environmental principles enshrined in the EC Treaty and project-specific practices and standards incorporated in EU secondary legislation on the environment. Seen from this perspective, Europeanization seems essential to the implementation of both regulatory regimes that are difficult to avoid and policies based on the exchange of information and ideas, flexible coordination, moral pressures exercised by peers and incentives. [START_REF] Bulmer | Germany, Britain, and the European Union: Convergence Through Policy Transfer[END_REF] The increasing role of both the EU and international organizations like the UN in public policies on the environment in Turkey might, in addition to policy transfer studies, be analyzed through the notion of "referentials." [START_REF] Muller | Les politiques publiques comme construction d'un rapport au monde[END_REF] Pierre Muller has written how development plans were influenced by a weltanschauung focused on modernization. A development plan was, according to Muller, a nexus for the elaboration of what he would later call a "modernizing referential." 42 From Turkey's perspective, CC policies were what development plans were to France; they play the same modernizing role to the extent that they are defined as an area gathering a variety of actors that represent the desire of respectability of a country but also the desire for the professionalization and rationalization of an administration that for a long time lacked experts. In this sense, they are based on a desire for both modernization referentials and prestige referentials.

[

  It covers] the EU 25 and European Economic Area (EEA) countries, the EU Acceding, Candidate and potential Candidate Countries and the Countries that are covered in the 'European Neighbourhood and Partnership Instrument. […] the projects in this region should comply with any obligations and standards enshrined in relevant Multilateral Environmental Agreements (MEAs)." 38 *** PULLOUT Turkey focused on adaptation to EU norms on the protection of the environment, agriculture, forests and pastures ***Turkey focused on adaptation to EU norms on the protection of the environment, agriculture, forests and pastures. A number of laws concerning the protection of natural sources, the pollution of irrigation water, regulations on drought and the loss of aquatic surfaces, the use of water and soil and on the foundation of agricultural unions were designed and implemented between 2005 and 2008.39

Table 1 : Major foreign-funded CC projects in Turkey

 1 of public projects on the environment allows us to observe that a great number of them are devoted to adaptation to and mitigation of CC and that all projects are financed by foreign sources, mainly coming from EU countries or UN institutions such as the UNDP and the United Nations Environment Programme (UNEP). All projects include the participation of many NGOs and various other enterprises. A great deal of funding is obviously devoted to capacity building for the environment in Turkey.

	PROJECT TITLE	PROJECT LED BY	FINANCED BY	BUDGET	NATURE OF PROJECT
	Preparation of	Environment	Global	$405,000 Report on
	the first national	Ministry and the	Environment		assessment/
	communication	Council for	Facility		Adaptation-
	on CC	Coordination on CC	(UNDP)		mitigation actions
	(2005-2006)

The parties included in Annex I are industrialized countries that were members of the OECD in 1992, as well as countries with economies in transition, especially the Russian Federation, the Baltic states and number of countries from central and eastern Europe. One of the obligations for the included parties is to adopt certain policies and measures in order to mitigate climate change by reducing greenhouse gas emissions to the levels of the 1990s. The parties included in Annex II are members of the OECD included in the Annex I excepting countries with economies in transition. These countries are obliged to provide financial sources in order to allow developing countries to undertake the necessary actions to reduce greenhouse gas emissions as provided by the convention and to better adapt to CC effects.


Timothée De Goussencourt
email: timothee.de-goussencourt@gipsa-lab.fr

Jean Dellac
email: jdellac@solidanim.com

Pascal Bertolino
email: pascal.bertolino@gipsa-lab.fr

A game engine as a generic platform for real-time previz-on-set in cinema visual effects

Keywords: Depth map, Real-time, Compositing, Virtual Production, Previz on-set, Real-virtual interaction, Unity

We present a complete framework designed for film production requiring live (pre) visualization. This framework is based on a famous game engine, Unity R . Actually, game engines possess many advantages that can be directly exploited in real-time pre-vizualization, where real and virtual worlds have to be mixed. In the work presented here, all the steps are performed in Unity: from acquisition to rendering. To perform real-time compositing that takes into account occlusions that occur between real and virtual elements as well as to manage physical interactions of real characters towards virtual elements, we use a low resolution depth map sensor coupled to a high resolution film camera. The goal of our system is to give the film director's creativity a flexible and powerful tool on stage, long before post-production.

Introduction

Since the beginning of film industry, movie makers like to compose a final scene by taking parts from different sources. With the coming of computer graphics in 90's it became possible to generate virtual graphics (assets) such as virtual backgrounds or virtual characters and to mix them with real images.This action is commonly called compositing. It must deliver a final image in accordance to the storyboard and the film director's wishes. At the moment, this is most of the time a post-production process taking a lot of time and money. Previz onset is an emerging discipline in film production to achieve live previzualisation. It fills the gap between the storyboard or the full 3D preview sequence (a.k.a. animatik) and the final image (figure 1). The main objectives of previz on-set is to improve film's director creativity during filming and also to speed-up the post-production step.

The solution that we present is a novel and distorted usage of a well-know tool of the game designers, namely the video game engine. With it, the output real-time previz provided to the film's director is built from several inputs: the HD images from the film camera, the virtual assets from 3D libraries, the depth map of the scene provided by a depth sensor and the interaction between the real world and the virtual assets. The software we chose, that permits this real-time mixing is the powerful and widely-used video game engine Unity R [START_REF]Unity Game Engine[END_REF]. Not only Unity is able to handle and merge the above elements in real-time but it also provides a built-in interface that allows an operator to edit in real time the content of the resulting scene without any extra complex coding. However, Unity is quite open and it is rather simple to implement specific real-time processing with shaders as it is mandatory in the kind of application we tackle. Apart from a first use of Unity R in previz [START_REF] Northam | A collaborative real time previsualization tool for video games and film[END_REF] but only for the visualisation of special effects, to our best knowledge our work is the first one to use a game engine in the particular field of previz and more generally in the mix of virtual and real worlds. In [START_REF] De Goussencourt | Using the unity game engine as a platform for advanced real time cinema image processing[END_REF], we presented a preliminary version of this work. The novelty and originality of the proposed work is that we show that using a game engine is also efficient for the following aspects: (1) managing physical interactions between real and virtual worlds, (2) coupling our previous system with a camera tracking system, (3) re-using all the information captured in real-time in post-production, (4) improving the realism of the virtual assets with the real scene lighting. At last, the results presented here are also more numerous than in [START_REF] De Goussencourt | Using the unity game engine as a platform for advanced real time cinema image processing[END_REF]. This paper is outlined as follows: in section 2 we present some technical background features that are the bases of our solution and we compare them with relative works on this field. Section 3 describes the main points of our approach and how they are technically implemented into the game engine. The paper will be concluded with some results in section 4.

Technical background

The depth information of the real scene is mandatory in previz applications and it must provided by a fast hardware system. Among them, the first generation of Kinect is based on an active stereo techniques using structured light [START_REF] Shpunt | Three-dimensional sensing using speckle patterns[END_REF]. The use of an infrared pattern has the advantage not to disturb the visible spectral domain of the scene. Another technique using infrared is the time of flight (ToF) technology in which the time that it takes for an infrared ray to hit an object of the scene and go back to the sensor is measured, providing the corresponding depth [START_REF] Burak Gokturk | A time-of-flight depth sensorsystem description, issues and solutions[END_REF]. The second version of the Kinect we are using in this work uses this technology and is a good compromise in terms of price and quality. The system we present is designed for indoor small scale scenes, in a controlled environment which may correspond to an important part of virtual production needs.

Some techniques to mix high definition color frames with depth sensors have already been developed. For instance [START_REF] Boisson | Fusion of kinect depth data with trifocal disparity estimation for near real-time high quality depth maps generation[END_REF] uses a trifocal rig to generate high precision depth maps: the authors combine a stereo system with a monocular depth sensor, similar to [START_REF] Zhu | Fusion of time-of-flight depth and stereo for high accuracy depth maps[END_REF][START_REF] Hahne | Combining time-of-flight depth and stereo images without accurate extrinsic calibration[END_REF][START_REF] Song | Combining stereo and time-of-flight images with application to automatic plant phenotyping[END_REF][START_REF] Gandhi | High-resolution depth maps based on tof-stereo fusion[END_REF]. Then, a complex global optimization workflow is needed to merge data. [START_REF] Patra | High resolution point cloud generation from kinect and hd cameras using graph cut[END_REF] uses a graph-cut optimization whereas [START_REF] Ferstl | Image guided depth upsampling using anisotropic total generalized variation[END_REF] formulates a convex optimization problem to make depth image upsampling. All of these methods use custom rigs. The Arri company develops a prototype coupling professional video sensor with a ToF depth sensor [START_REF] Hach | A novel rgb-z camera for high-quality motion picture applications[END_REF]. Conversely, the method we propose can deal with every film camera.

Our fusion method is implemented into the popular game engine Unity [START_REF]Unity Game Engine[END_REF]. This platform was chosen because of its great versatility and huge developers community. The graphics engine incorporated into Unity is built on top of most modern graphics API, achieving real-time rendering performance, which was an important prerequisite for our project. In our case, the Unity software is not used to build a game but to perform and display real-time image processing.

An important step of our method is compositing. Traditional compositing techniques are using a layer scheme, where all objects of the scene are precisely ordered from the closest to the furthest layer. This kind of representation is static and does not permit all the occlusion cases. In our case the final preview image is generated by composing the virtual frame with the real one regarding the depth values of their content. This technique is called depth based compositing. The registered depth maps of virtual and real scenes are compared on the GPU to generate a per pixel matting mask [START_REF] James F Blinn | Compositing. 1. theory[END_REF]. One of the big challenges of compositing is to ensure seamless integration of virtual layers with the camera footage [START_REF] Klein | Compositing for small cameras[END_REF]. In our method we focus particularly on automatic lighting and grading.

In order to add automatic interaction between real world and virtual contents, we also use body segmentation functionalities provided by the Kinect SDK [START_REF] Shotton | Real-time human pose recognition in parts from single depth images[END_REF]. Some related works dealing with real/virtual mixing can be found in [START_REF] Bartczak | Integration of a time-of-flight camera into a mixed reality system for handling dynamic scenes, moving viewpoints and occlusions in real-time[END_REF][START_REF] Izadi | Kinectfusion: real-time 3d reconstruction and interaction using a moving depth camera[END_REF].

This section lists the main contributions of the game engine as a natural and powerful platform for previz on-set 2. We show that the main following steps of previz are successfully addressed through Unity: acquiring and registering the data flows, controlling the scene, compositing the scene by mixing real images and virtual workflow, lighting the virtual assets, managing physical interactions between an actor and virtual objects, creating data backup of the whole for post-production.

Image acquisition

A key point of our approach is to use the depth of the real scene. To that purpose, a Kinect 2 depth sensor is rigidly fixed to a high resolution film camera as shown in figure 3. The sensors baseline is minimized in order to avoid shadow problems.

The calibration of the two cameras is classical and is performed offline: the intrinsic parameters of each camera are retrieved. Then an extrinsic calibration is done to compute the relative position of the depth sensor to the film camera. A well-known technique for calibrating a camera is based on chessboard pattern recognition [START_REF] Zhang | Flexible camera calibration by viewing a plane from unknown orientations[END_REF][START_REF] Zhang | A flexible new technique for camera calibration[END_REF]. This calibration is computed only once at the beginning, all calibration parameters are saved, then loaded to the game engine at run time.

The HD color video stream is transferred from the film camera to the computer with an SDI to USB3 acquisition card. The HD color frame (1920 × 1080 pixels) is stored in a 2D texture, a specific structure that the GPU can handle. About the depth, the sensor delivers a 512 × 424 pixels resolution, 16 bits per pixel, real-time depth map. The color sensor available on the Kinect 2 is not used. This buffer is also stored into a 2D texture structure, for a GPU use. As there is no trigger input in the Kinect to synchronize it with an external clock, we set up a circular frame buffer where each depth frame is stored with its corresponding timestamp. When a film frame arrives, the closest (in time) depth frame is selected and associated to the HD color frame. This is a way to compensate the small delay that can occur between depth and color streams.

Depth and color image registration

The acquired HD color images and depth images do not fit at all: the pixel density of the color image is much higher than the one of the depth image: in our context, 1 depth pixel correspond to about 30 color pixels. Furthermore, the field of view of the depth sensor is fix and may largely differ from the one of the HD camera that depends on the used lens. The dense registration of the depth image with the color image is performed in Unity with a shader. Shaders are small scripts that are executed by the GPU. In this particular case, the shader is used to back-project the 3D information from the depth sensor into the main camera screen space, for each frame. The current depth texture and a grid mesh with the dimension of the depth map (512 × 424 vertices) are sent to the GPU. Each vertex is displaced in regards to the depth map value and the depth sensor intrinsic parameters. This way a 3D representation of the scene is computed in real-time using GPU capabilities. This 3D mesh is now observed according to the film camera point of view using the calibration settings. Re-projection of the low resolution depth map becomes a dense interpolation, fitting the resolution of the film camera. More details are presented in [START_REF] De Goussencourt | Using the unity game engine as a platform for advanced real time cinema image processing[END_REF]. Note that shaders may also be used for many kernel-based image filtering.

Editing and controlling

A game engine is commonly used to render in realtime a virtual scene. This is an optimised framework to deal with a lot of 3D assets, lighting and physical interactions. In our context we consider the game engine as a powerful video mixer. Several inputs are mixed together to produce the preview image, using all the great features a game engine can offer. You can program the game engine behaviour by scripting functions placed in a main loop scheme. Each time a new film frame is rendered, this main loop is called and executed.

Unity also provides a live editor mode to control in realtime each parameter of each element of the virtual scene, with a graphic user interface (GUI). That means you can modify or tune many things online: lighting parameters, add 3D assets, displace virtual contents, trig animation . . . The main control settings are already included in the game engine framework, and it is also easy to add custom controls relative to your scripts into the editor interface. This point is important because the user is thus able to change online the layout of the scene in order to answer the film director's wishes. Is is also possible to build your scene as a standalone executable to achieve better performances. In this case you should construct a GUI control panel to allow online editing of the 3D scene.

Depth based compositing

The final step of our pipeline is the compositing of all the virtual assets with the real scene with the handling of occlusions. The point of view of the virtual scene render is either defined by hand for a static camera shot or possibly triggered by a camera tracking system for a moving shot. This render point of view, defined by a virtual camera, matches the pose and lens configuration of the real film camera. This way the virtual frame perfectly overlaps the film frame.

To handle occlusions we ask the game engine to grab the depth map of the virtual content. Then it is possible to compare the real scene depth map with the virtual scene depth map to generate a binary mask coding whether a pixel of the final rendering comes from the virtual asset frame or from the film camera frame. This mask is smoothed using a blur filter to attenuate hard discontinuities between background and foreground. The final compositing is then computed using the classic over operator [START_REF] James F Blinn | Compositing. 1. theory[END_REF], see Figure 4.

Automatic lighting and grading

In order to blend seamlessly the virtual assets with the real world we need to replicate the lighting [START_REF] Paul | Recovering high dynamic range radiance maps from photographs[END_REF] and color response [START_REF] Knecht | Adaptive camera-based color mapping for mixed-reality applications[END_REF] of the real scene. To achieve that, a unique high dynamic range image (HDRI) of the scene using a 360 • camera (figure 5, top) is captured offline. Then the Greta MacBeth ColorChecker is used to calculate two transfer functions A and B stored into look up tables (LUT) (figure 5, bottom). A transfers a neutral colorspace (sRGB) to the colorspace of the film camera. B transfers the colorspace of the 360 • camera to a neutral colorspace. The HDRI is transformed to the neutral colorspace using B. Then the result is used to light the virtual assets in neutral space using image based lighting (IBL). Finally A is applied to the rendered virtual elements, so they match the color response. Unity natively supports a real-time optimised IBL system, again with the use of a shader. The color checker can be seen on each side of the picture. Bottom: LUT that maps the HDRI colorspace to a neutral colorspace stored into a 2D texture

Interaction between real and virtual elements

Game engines include interesting features like physics engine. That means each virtual element could physically behave like real objects. It is possible to set-up a gravity, a mass for each object and a collision detection. In our case we focus on interaction between real actors and virtual objects. Even if is technically possible to compute collision with the detailed mesh from the depth map, this will affect real-time performances. We solve this problem by using a 3D schematic representation of the human skeleton of the actors. Human pose recognition is computed with a method described in [START_REF] Shotton | Real-time human pose recognition in parts from single depth images[END_REF] and included in the Kinect SDK.

When a 3D skeleton collides with a virtual object, the game engine trigs an event. This event can be bound to a script where any physical action can be planned. An example of brick wall destruction is showed in figure 6.

Data backup and post processing

Previz on-set is a precious help during shooting but this is not the end of the film building process. The second main role of previz is to facilitate and improve post-production. To do this, each data stream (depth, camera tracking) is backuped independently during the shooting. This way it is possible to virtually replay the scene, but this time without any realtime constraint. But even is it possible to slow down a game engine to achieve a better rendering or give more time to computation, it is optimised for real time. So, some professional software are dedicated to compositing, such as Nuke [START_REF]Nuke, the Foundry[END_REF] or Natron [17], and very popular in post-production studios. This is why we choose to convert the data into an openEXR [START_REF]OpenEXR[END_REF] image sequence. This format was originally developed by Illuminated Light and Magic and it is now a standard in film industry. It supports multi-channels and until 32bits precision per channel. It is also possible to add custom information in headers, like 3D pose of the camera. This way previz data are stored into a well known formalism that professionals are used to work with.

Experiments

The computer used for our experiment is a laptop with an Intel i7 2.8GHz processor, 16Go RAM and a Nvidia Quadro K4100M. The Unity version 4 and 5 were also used. Our system was tested with two different film cameras used traditionally for broadcast applications (see Figure 3). Their setup includes a 18mm lens mounted on a Panasonic AG-AF100A and also a 14mm lens mounted on a Blackmagic Studio HD camera.

Our compositing results are presented in figure 7. In this sequence we coupled our method with the camera tracking system SolidTrack [START_REF]Solidanim SolidTrack system[END_REF]. This allows us to move the camera freely, conserving the right virtual point of view to render 3D assets. Examples of interaction between an actor and virtual objects are shown in figures 8 and 9. The depth information is used to compute compositing, while a 3D schematic skeleton trigs in background the collision events. The first example shows a brick wall destruction whereas the second one shows hit weightless objects. Figure 10 shows the effect of color transfer to improve the rendering coherence between virtual and real contents. The overall method described here reaches real-time performance to deliver preview image synchronized with the film camera framerate. Some live video samples captured on the laptop screen are available at https://sites.google.com/site/pascalbertolino/previz2. As one can see, the results are not perfect, due to the low quality of the depth map. The depth frame is noisy, and it is quite noticeable at edge. Moreover, the baseline between the film camera and the depth sensor introduces some holes in the registered depth map. But keep in mind that we are looking for previz images: in film industry, the final image is post-processed manually to get the best possible results. However, we plan to perform some guided filtering in order to improve the depth map quality by injecting the film image inside the kernel filter computation. Our method is based on an extension of the joint bilateral filter [START_REF] Kopf | Joint bilateral upsampling[END_REF] described in [START_REF] Garcia | Pixel weighted average strategy for depth sensor data fusion[END_REF].

Conclusion

In this article we argue why to use a game engine as a platform for previz onset. A game engine offers nice features: optimised for realtime, rendering and physical engine capabilities. This platform is well adapted on stage and it is adaptive and generic in regards to cameras and specific image processing. The current framework we described here is used in the context of the PREVIZ project [START_REF] Briand | On-set previsualization for vfx film production[END_REF] dedicated to virtual production, especially previz on-set. All data are recorded online to be re-used in post-production. This way previz on-set is also used as a guide for final compositing. In the future, using this framework, we will propose a database coupling film camera footage with registered depth maps and possibly camera tracking data. This database will be made to better understand how the data produced in previz can be used in post-production.

Fig. 1 .

 1 Fig. 1. Film building process. From left to right: first row: storyboard and animatik. Second row: previz on-set and post-production final compositing. ( all images from the PREVIZ project )

Fig. 2 .

 2 Fig. 2. Overall system workflow. Offline process is executed once at the beginning. Online process is executed in real-time for each frame into the game engine. Blocks marked by a * use shaders in their process.

Fig. 3 .

 3 Fig. 3. Our system using different film cameras coupled with the Kinect 2. Left: Blackmagic Studio HD with 14mm lens. Right: Panasonic AG-AF100A with a 18mm lens

Fig. 4 .

 4 Fig. 4. Example of compositing. Left: first row: film frame and registered depth map, second row: virtual character frame and depth map. Middle: binary mask. Right: final compositing

Fig. 5 .

 5 Fig. 5. Top: sample of a 360 • high dynamic range image used to light the virtual assets.The color checker can be seen on each side of the picture. Bottom: LUT that maps the HDRI colorspace to a neutral colorspace stored into a 2D texture

Fig. 6 .

 6 Fig. 6. Interaction example. Left: skeleton detection in the depth map. Right: 3D representation of the skeleton in the game engine editor. Collision detection between the skeleton of the real actor and the virtual brick wall

Fig. 7 .Fig. 8 .Fig. 9 .Fig. 10 .

 78910 Fig. 7. Camera tracking and occlusions. Filmed with the Panasonic AG-AF100A camera with a 18mm lens coupled with the SolidTrack camera tracking system


Antoine Barbieri

Myriam Tami

Xavier Bry

David Azria

Sophie Gourgou

Caroline Bascoul-Mollevi

Christian Lavergne

Analyse longitudinale de la qualité de vie en cancérologie par modèles à équations structurelles et à effets aléatoires

Première étape (transversale)

f 1 f 2 X 1 c 1 c 2 a 1 X 2 a 2 T 2 y T 1 D 1 D 2

T d

Légende:

Facteurs

Résultats transversaux

Score du groupe 1 uniformément plus bas Tab. 2 : Estimations des paramètres p associés à la matrice D1 du SEM Observations indépendantes et gaussiennes

Résultats longitudinaux

f m ~N(0,Id n ) pour m=1,2 f 1 et f 2 mutuellement indépendants ε i y ~N(0,σ y 2 ) ; ε i m ~N(0,σ m 2 Id q m )
où q m le nombre de variables du bloc m.

Seconde étape (longitudinale)

  Barbieri, A., Tami, M. et Al. (Being written) EM algorithm in a structural equation modeling for longitudinal study of quality of life. Aaronson, NK et al. (1993). The European Organization for Research and Treatment of Cancer QLQ-C30: a quality-of-life instrument for use in international clinical trials in oncology. 85(5):365-376. Azria D, Belkacemi Y, Romieu G et al. Concurrent or sequential adjuvant letrozole and radiotherapy after conservative surgery for early-stage breast cancer (CO-HO-RT): a phase 2 randomised trial. The Lancet Oncology 2010; 11(3): 258-265.

  Fig. 2 : Schéma du SEM relatif à la construction des questionnaires EORTC

Fig

  Fig. 3 : Corrélation entre les facteurs estimés avec (abscisse) et sans (ordonnée) la prise en compte de la variable associée au groupe dans les différents blocs de mesure.

L

  'évolution de la QdV globale est modélisée au travers d'un modèle linéaire mixte (LMM), où le QL2 (y) est expliqué par des variables explicatives (dont les deux variables latentes reconstruites) et un effet individu (effet aléatoire) tel que : Avec α une constante, β le vecteur des effets fixes du modèle, ξ i le vecteur des effets aléatoires (normalement distribués) spécifiques au sujet i et ε iv le terme d'erreur (normalement distribué).ConclusionsEssai CO-HO-RT (cancer du sein)Phase II comparant l'association du létrozole et d'une radiothérapie après chirurgie et chimiothérapie.Données de QdVQuestionnaire générique QLQ-C30 et module complémentaire QLQ-BR23 spécifique au cancer du sein : 7 dimensions fonctionnelles, 12 dimensions symptomatiques, statut global de santé. La capacité fonctionnelle globale semble être moins bonne lors des visites à 12 et 21 mois lorsque l'administration se fait de manière séquentielle, Aucun argument clinique n'explique ces différences ponctuelles. Aucune différence entre les deux groupes Part individuelle et part des facteurs importantes pour expliquer le QL2 Cette approche globale de l'analyse de la QdV permet de réduire/éviter les tests multiples par l'intermédiaires de facteurs résumant le statut fonctionnel et le statut symptomatique du patient. L'évaluation de l'impact de covariables s'effectue ponctuellement (SEM) et également au cours du temps (LMM). proposer une Nouvelle Approche qui tient compte conjointement de l'aspect longitudinal et de la nature multidimensionnelle de la QdV.

Fig

  Fig. 1 : Décomposition de la Qualité de Vie relative à la santé (QLQ-C30 & QLQ-BR23)