Physico-realistic image synthesis and materials elaboration for automative industry

The LIMA project (Light – Interaction – MAterials) originates from three research laboratories at MINES ParisTech: the Center for Mathematical Morphology (CMM), the Robotics Lab (CAOR) and the Center for Materials (MAT), as well as from the Center for Materials (C2MA) from the Alès Mines School. Several companies, including PSA Peugeot Citroën are assocaietd to the project. The project’s goal is the physico-realistic simulation, by a rendering engine, of the visual appearance of materials – and the development of tools for interactive visualization of synthesis images realized by virtual reality techniques.

The project allows to increase productivity and diminuish costs associated to the conception of paints, for instance in automotive industry. Other possible applications include the development of new pigments for the chemical industry or the simulation of visual appearance of components in the cosmectic industry.

The project and, theoretical, numerical and experimental tools are based on a methodology, comprised of the following five key steps.

Material production: creation of “model materials” containing hematite pigments of various shapes (nanocubes, nano-cigars, spindles) at the nanoscale. The pigments size is much smaller than the light wavelength in the visible spectrum. The composition of the material is accordingly controlled. The material is notably used to test and validate numerical models developed in the project. Second, a paint layer furnished by PSA Peugeot Citroën, partner of the project, composed of metal flakes at the micronic scale, visible by the human eye, is studied.

Measurements: use is made of modeling techniques and measurements, from the nano- up to the macroscopic scale: preparation and synthesis of nano-materials, statistical measurements of the morphology of pigments and of their spatial distribution, measurement at small and large scales of the dielectric functions and refractive index.

Modeling: using numerical means, creation of random morphological models representative of the heterogeneous materials. Numerical homogenization tools are used to predict optical properties, which are validated experimentaly. A 3D rendering engine link the scales of the material and pigments, or flakes, and that of human observation. The later induce sparkling effects which appear and disappear when the angle and distance vary.

Visual rendering: validation of the simulation in a rendering engine for both “model materials” and industrial paint layers, inclusing the reproduction of the sparkling effects using the morphological model for flakes distribution.

Perceptive validation: vision is a dynamic sense, motion with respect to objects is crucial in binocular vision. To include perceptive indices for materials, the project integrates virtual reality techniques (stereoscopy, dynamic perspective using motion capture) in the rendering engine. This allows to validate simulations at the human scale and their optical relevance.

Perceptive validation of a realistic simulation of a material using virtual reality

Several important results have already been obtained: the validation of the simulation, using numerical methods and random morphological models, of the optical properties of a hematite material, and the partial reproduction of the sparkling effect, as well as a morphological model for flakes distribution. Virtual reality techniques have been integrated in the rendering engine and their relevance for visual observation were measured for various configurations.

The year to come will be used to refine geometrical models, integrate more complex models and improve the rendering engine. More work will be devoted to improving the interface, allowing for visual comparisons between virtual models and materials, and on the study of materials with metal flakes.

The LIMA project has been labelized by MOV’EO (research and development for automotive and public transport) and Systematic Paris Region. 15 researchers including 5 PhD students are currently working on the project.

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The financial support of ANR (French National Agency for Reasearch) is acknowledged. The project “LIMA” is conducted in partnership with the Center for Mathematical Morphology (CMM), the Robotics Lab (CAOR) and the Center for Materials (MAT), part of the Mathematics and Systems department of Mines ParisTech, the Center for Materials (C2MA) from Mines d’Alès, the INSP (Institute for NanoSciences in Paris), and the companies PSA Peugeot Citroën, Eldim, Naxagoras and Scalable Graphics. The 4-years project was started in january 2012, with 2.5 million euros budget.

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