Electro-Optic simulation related publications

The following publications have been made by the OKTAL-SE research and development team in relations with reseach institutes in France and in Europe.

• Aircraft infrared signature, taken into account body, engine and plume contributions
  ITBMS 2009
  The IR signature of an aircraft is the result of several major contributions, namely:
  • Hot engine parts of the tail pipe and/or the air intakes
  • Combustion hot gases (and in some cases hot carbon particles) in the plume
  • Skin of the airframe, due to the thermal emission resulting from aerodynamic heating and internal heat sources and the reflected ambient radiation from the sun, the sky and the ground.
  
  The aim of this paper is to explain how the combination of CFD++, CFD computational code, RadTherm-IR, 3D thermal computational code and SE-Workbench-EO from OKTAL-SE is an adequate solution for computing the IR signature of a jet aircraft taking all this major into account.

• The coupling of MATISSE and the SE-WORKBENCH: a new solution for simulating efficiently the atmospheric radiative transfer and the sea surface radiation
  SPIE 2009
  The SE-WORKBENCH workshop, also called CHORALE (French acceptation for “simulated Optronic Acoustic Radar battlefield”) is used by the French DGA (MoD) and several other Defense organizations and companies all around the World to perform multi-sensors simulations. CHORALE enables the user to create virtual and realistic multi spectral 3D scenes that may contain several types of target, and then generate the physical signal received by a sensor, typically an IR sensor.
  MATISSE [4,5] is a background scene generator developed for the computation of natural background spectral radiance images and useful atmospheric radiative quantities (radiance and transmission along a line of sight, local illumination, solar irradiance …). Backgrounds include atmosphere, low and high altitude clouds, sea and land. A particular characteristic of the code is its ability to take into account atmospheric spatial variability (temperatures, mixing ratio, etc) along each line of sight. An Application Programming Interface (API) is included to facilitate its use in conjunction with external codes.
  The paper will demonstrate the advantages for the SE WORKEBNCH of using MATISSE as a new atmospheric code, but also for computing the radiative properties of the sea surface.

• Improvement of global illumination methods for infrared rendering of outdoor scenes including targets
  ITMBS 2008-1
  In this paper, we describe the recent evolutions of SE-RAY-IR that concerns improvements, firstly, of the physical materials description using a BRDF well fitted to complex materials and secondly of the rendering algorithm. We present a new highly configurable hybrid approach that takes the best-suited methods for each simulated phenomena among a set of literature rendering methods. It enables to compute highly realistic simulation of outdoor scenes, taking into account skylight multiple reflections, extended sources and glossy reflections.

• Improvement of the SE-WORKBENCH workshop for rendering targets
  ITMBS 2008-2
  The SE-WORKBENCH workshop, also called CHORALE, is used by the French DGA to perform multi-sensors simulations. The SE-WORKBENCH enables the user to create virtual and realistic multi spectral 3D scenes that may contain several targets, and then generate the physical signal received by a sensor.
  One of the main current interests for the DGA is to be able to compute the infrared (IR) signature of targets in their environment as accurately as possible, even if the targets are coated with a special paint for improving their stealthness. But for that the SE-WORKBENCH workshop needs to be improved as regard to the BRDF (Bidirectional Reflectance Distribution Function) modelling of the materials.

• Building generation for Multi-Sensor Simulation
  ITMBS 2007-1
  Urban Warfare training can be achieved with infrared/NVG embedded sensors, such sensors can also be used for infrared image recognition and target identification training. In the infrared domain, the 3D representation of a facade is necessary in order to have realistic representation with regards both to thermal computation and thermal effects. In the radar domain, this type of facade modelling is quite necessary with regards to edge and corner reflection effects. During the specifications of infrared enhanced vision systems or infrared embedded security systems, the usage of simulation reduces the cost and time required to validate a product. But to ensure the reliability of such virtual simulation, it is necessary to use a large panel of simulation tests. Creating these tests, and especially the one in urban area could be time consuming. The capacity to quickly generate credible digital city models helps the users to achieve their studies. Detailed modelling of realistic towns is a real challenge for computer graphics. Modelling a virtual city that is detailed enough to be credible is a huge task that requires lots of hours of work. In this context, automatic approaches can bring a real added value. We present a new technique to automatically generate building exteriors. Our technique relies on the definition of building templates that will be applied on building descriptions. Building frontages are generated using a 2.5D wall grammar based on a set of rules that can be simple or detailed enough to fulfil the users wishes. Our method is as easy to use as the texture repetition but provides a higher level of realism and diversity in the resulting buildings. Then little information is necessary to generate a whole building: the walls and roof height, the building 3D footprint and the chosen template. This information can be stored within a Geographic Information System.

• SE-RAY-IR improvement: an advanced illumination approach for infrared rendering of outdoor scenes
  ITMBS 2007-2
  In this paper, we describe the evolutions of SE-RAY-IR. The first evolution concerns an improvement in the description of physical materials using a BRDF model which describes complex materials (from user defined analytical models to measured data sets). The second improvement concerns the rendering algorithm. We propose a highly configurable hybrid approach which takes the best suited method for each simulated phenomena among a set of literature rendering methods. Then our hybrid approach benefits from their respective advantages. It enables the computation of highly realistic simulation of outdoor scenes, taking into account sky light multiple reflections, extended sources and glossy reflections.

• Simulation of active and passive infrared images using the SE-Workbench
  SPIE 2007
  The SE-WORKBENCH workshop, also called CHORALE (“simulated Optronic Acoustic Radar battlefield”), is used by the French MoD/DGA to perform multi-sensors simulations by creating virtual realistic multi spectral 3D scenes and then generating the signal received by a sensor. Taking advantage of developments made in the frame of Radar simulation, CHORALE is currently enhanced with new functionalities in order to tackle the “active” problem, involving new generation of infrared sensors such as laser radars. This article aims at presenting the challenges for simulating simultaneously passive IR imagery of a full terrain and active imagery especially on targets. We insist on duality and differences concerning in particular monochromatic/coherent waves versus incoherent waves, BRDF modeling taking into account surface roughness, polarization effects, Doppler effects.

• Real Time optronic simulation using automatic 3D generated terrain, and validation process
  ITBMS 2006
  The SE-Workbench technology is used to perform multi-sensors simulations on complex 3D synthetic environment. The SE-Workbench enables the user to create virtual and realistic multi spectral 3D scenes, and generate the physical signal received by a sensor, typically infrared (IR), radar (EM) and acoustic (AC) sensors. To evaluate the efficiency of visible and infrared sensors, simulation tools that give a good representation of physical phenomena, are used. This article describes the elements used to prepare data (3D database, materials, atmosphere, …) for the simulation, and the set of tools (SE-FAST-IR), used in the SE-Workbench-IR for the Real Time simulation in the infrared spectrum. The SE-AGETIM tool turns geographical source data (including GIS facilities) into meshed geometry enhanced with the sensor physical extensions, fitted to the ray tracing rendering of the SE-Workbench and to the Real Time rendering capabilities of the SE-Workbench in infrared. The SE-FAST-IR package allows the compilation and visualization of 3D databases for infrared simulations. It enables one to visualize complex and large synthetic scenes for a wide set of real and pseudo-real time applications. The SE-FAST-IR software automatically computes radiance textures, Open GL light source and fog-law parameters for predefined thermal and atmospheric conditions specified by the user. It is based on the physical model used by the ray-tracing tool of the SE-Workbench, which enables the development of a coherent and powerful validation method.

• Automatic 3D virtual scenes modeling for multi sensors simulation
  SPIE 2006
  SEDRIS that stands for Synthetic Environment Data Representation and Interchange Specification is a DoD/DMSO initiative in order to federate and make interoperable 3D mocks up in the frame of virtual reality and simulation. This paper shows an original application of SEDRIS concept for research physical multi sensors simulation, when SEDRIS is more classically known for training simulation. CHORALE (simulated Optronic Acoustic Radar battlefield) is used by the French DGA/DCE (Directorate for Test and Evaluation of the French Ministry of Defense) to perform multi-sensors simulations. CHORALE enables the user to create virtual and realistic multi spectral 3D scenes, and generate the physical signal received by a sensor, typically an IR sensor. In the scope of this CHORALE workshop, French DGA has decided to introduce a SEDRIS based new 3D terrain modeling tool that enables to create automatically 3D databases, directly usable by the physical sensor simulation CHORALE renderers. This AGETIM tool turns geographical source data (including GIS facilities) into meshed geometry enhanced with the sensor physical extensions, fitted to the ray tracing rendering of CHORALE, both for the infrared, electromagnetic and acoustic spectrum. The basic idea is to enhance directly the 2D source level with the physical data, rather than enhancing the 3D meshed level, which is more efficient (rapid database generation) and more reliable (can be generated many times, changing some parameters only). The paper concludes with the last current evolution of AGETIM in the scope mission rehearsal for urban war using sensors. This evolution includes indoor modeling for automatic generation of inner parts of buildings.

• Real time simulation tools in the CHORALE workshop
  SPIE 2006
  CHORALE (simulated Optronic Acoustic Radar battlefield) is used by the French DGA/DET (Directorate for Evaluation of the French Ministry of Defense) to perform multi-sensors simulations. CHORALE enables the user to create virtual and realistic multi spectral 3D scenes, and generate the physical signal received by a sensor, typically an IR sensor. To evaluate their efficiency in visible and infrared wavelength, simulation tools, that give a good representation of physical phenomena, are used. This article describes the elements used to prepare data (3D database, materials, scenario, …) for the simulation, and the set of tools (SE-FAST-IR), used in CHORALE for the Real Time simulation in the infrared spectrum. SE-FAST-IR package allows the compilation and visualization of 3D databases for infrared simulations. It enables one to visualize complex and large databases for a wide set of real and pseudo-real time applications. SE-FAST-IR is based on the physical model of the Non Real Time tool of CHORALE workshop. It automatically computes radiance textures, Open GL light source and fog-law parameters for predefined thermal and atmospheric conditions, specified by the user.

• Obscurant representation improvements in the CHORALE workshop
  SPIE 2005
  CHORALE (simulated Optronic Acoustic Radar battlefield) is used by the French DGA/DET (Directorate for Evaluation of the French Ministry of Defense) to perform multi-sensors simulations. CHORALE enables the user to create virtual and realistic multi spectral 3D scenes, and generate the physical signal received by a sensor, typically an IR sensor. Some assessments concern the study of the duality between a threat (a missile for example) and a target (a battle tank for example) in the battlefield. In these cases, obscurants are special counter measures (clouds), classically used to hide armored vehicles and/or to deceive threatens. To evaluate their efficiency in visible and infrared wavelength, simulations tools, that give a good representation of physical phenomena, are used. The first part of this article describes the elements used to prepare data for the simulation. The second part explains the physical model used in CHORALE for the resolution of the Radiative Transfer Equation when obscurants are set in the scene. Obscurants are modeled by a set of voxels (elementary volume elements). Each voxel contains the spectral absorption and scattering coefficients, phase function coefficient and temperature information. The shape is changing with time to take into account the dynamic evolution of the obscurant. A “photon map” method is used in the ray tracing process to take into account global illumination within the cloud and solve the Radiative Transfer Equation.

• Multi-pass Density Estimation for Infrared Rendering
  Pacific Graphics 2004 (submitted)
  We compute several little particle maps. All these particle maps are global in opposition to the localised particle maps dependent on the geometry of [13] which means that each particle map stores particles within the entire model. This ensures that the illumination is spread correctly over the scene for each pass and thus that density estimations are correct.We benefit from the speedup of computing multiple small particle maps shown in [13] without limitation on the mesh complexity because the particle maps are not dependent on the geometry. Unfortunately, when the image size is large (i.e 1024x768 pixels), the time saved while computing and sorting the particle map is lost when rendering due to the number of density estimations needed. Therefore, it is more interesting to compute fewer passes with bigger particle maps when rendering big images. The memory used is constant from one pass to another.

• Low Memory Spectral Photon Mapping
  WSCG 2004 (submitted)
  We showed how it is possible to adapt Photon Mapping to a spectral rendering without consuming extra memory while keeping a very good accuracy. Taking into account spectral emission and reflections permitted us to do accurate IR rendering. Our multi-pass method is faster than classical method when photon map fits entirely in memory. We can use an unlimited number of photons. We avoid problems due to photon map caching such as swapping and cache defaults. Thus our method can match very accurate results. This is very interesting for IR rendering, while we can through enough photons to have the noise disappeared.

• Obscurant representation for realistic IR simulation
  SPIE 2003
  Obscurant representation is a key component of ground battlefield simulation, especially in the infrared domain. Obscurant are special counter measures (clouds) classically used to hide armored vehicles and deceive threatens.
  Obscurants are very difficult to represent especially because of multi diffusion effects of hot particles and smoke, but this representation is very important to quantify the efficiency of the decoy.
  This article describes a new model being involved in the simulation workshop CHORALE of the French DGA [1], [2] & [3]. The simulation workshop CHORALE developed in collaboration with OKTAL SE company is used by government services and industrial companies for weapon system validation and qualification trials in the infrared domain. The main operational reference for CHORALE is the assessment of the infrared guidance system of the Storm Shadow missile French version, called Scalp. This new model, integrated in CHORALE, enables to simulate the emitted radiance and the transmission of any pre computed obscurant cloud in the virtual battlefield.
  In the modeling step, the cloud is defined by a set of “voxels” (elementary volume elements). Each voxel contains the spectral extinction coefficient and the spectral scattering coefficients. The shape, i.e. the voxels content, is changing with time to convey the dynamic evolution of the obscurant.
  In the Non Real Time rendering step, primary rays are traced inside the clouds. For each voxel, scattering rays are then traced to their neighboring voxels and the local hot sources. Actually, ray tracing is used to solve the Radiative Transfer Equation. The main advantage is to be able to solve it taking into account the synthetic environment: the local terrain, the target hidden in the cloud, the atmospheric and weather conditions. The main originality is the multithreading ray tracing which enables to tackle huge quantities of rays in complex geometric environment.
  

• Automatic Temperature Computation for Realistic IR Simulation
  SPIE 2000
  The thermal library of CHORALE and the associated software (MURET and TSC) allows a quick and accurate computation of temperature polygons of a 3D scene for realistic and physical simulations in the infrared domain. This software is specially fitted for temperature computation of “ground” and “building” type polygons. The future evolutions planed this year for CHORALE will allow a better temperature computation for permeable ground type polygons and for objects with internal heat sources (buried pipes, radiator behind a wall, …).

• Realistic multi spectral simulation including IR simulation
  SPIE 1999
  Multi sensor simulation is just starting and will certainly be a master piece of technology development. CHORALE is a pioneer step into this huge field of development. The concept is a winning concept because it is fitted to future natural evolution regard to simulation. The idea is to add other steps in the same direction always keeping in mind the main goal: increase the confidence level to the simulation realism.

• A usefull kernel to make realistic infrared simulation
  SPIE 1998
  Multi sensor simulation is just starting and will certainly be a master piece of technology development. ONDE then the KERNEL are two pioneer steps into this huge field of development. The concept is a winning concept because it is fitted to future natural evolution regard to simulation. The idea is to add other steps in the same direction always keeping in mind the main goal : increase the confidence level to the simulation realism.