Associate Team RTR2A :

Real-Time Rendering and Augmented Reality

Start: February 2004

The Teams:

Scientific description of the collaboration

The first objective is real-time high fidelity rendering of dynamic scenes. Rendering complex scenes using a classical graphics pipeline (Z-buffering, Phong's shading model, multitexturing, etc.) can be efficiently performed with commodity graphics cards. However, real-time rendering of scenes, for which global illumination is computed, still is a challenge for many researchers. Indeed, global illumination followed by a rendering step (that we call high fidelity rendering) is a demanding process in terms of computing and memory resources.

Computing global illumination amounts to solve the rendering equation which is an integral equation. Unfortunately, this equation does not have an analytic solution in general. Consequently, Monte Carlo integration is the method of choice for solving it. However, Monte Carlo integration requires the computation of many samples, which makes it demanding in terms of computation time. Our objective is to propose an algorithm which allows for interactive high fidelity rendering and global illumination.

Our approach makes use of ray tracing, Monte Carlo integration and caching. It aims at extending the ``irradiance caching'' algorithm (Greg Ward 1994). Note that this algorithm is based on the observation that the diffuse component of radiance, reflected on a diffuse surface and due to indirect illumination, changes very slowly on this surface. This allows to sparsely sample and to cache the incoming radiances at these samples, then to reuse the cached samples to estimate the incoming radiance at nearby points. This method is computationally efficient since the sampling is sparse. However it is limited to diffuse indirect lighting computation.

Our work consists in extending the irradiance caching approach to indirect glossy global illumination. Our algorithm relies on ``radiance caching''. It is based on the caching of directional incoming radiances. We have first designed a new set of basis functions defined on the hemisphere to represent directional incoming radiance and BRDFs (Gautron et al. 2004). This representation, along with a new gradient-based interpolation method (Krivanek et al. 2004), are the bases of our radiance caching-based algorithm. We are also experimenting with spherical wavelets to represent BRDFs and incoming radiances. Our radiance caching algorithm will intensively exploit the power of programmable GPUs (Gautron et al. 2005), to make global illumination more interactive. .

The second objective is augmented reality. We aim at combining in real time synthetic and real images. To this end, we propose to: calibrate the real images, extract the light sources which lighted the real scenes, insert synthetic objects in the real scene for which we dispose only of their images captured by a camera, and finally light these synthetic objects with the extracted real light sources. The result will help a user, supplied with a head mounted display, to see a real scene augmented with synthetic objects lit homogeneously.

For now, our collaboration has tackled only real-time high fidelity rendering. The results we obtained are:

People involved:

Missions already carried out

Publications

- Siggraph Skteches

-2006: P. Gautron, K. Bouatouch, S. Pattanaik, Temporal Radiance Caching, SIGGRAPH 2006 Sketches

- 2006: Kévin Boulanger, Sumanta Pattanaik, Kadi Bouatouch, Rendering Grass Terrains in Real-Time with Dynamic Lighting,
   Siggraph  sketch

- 2006: François Guillaume, Sumanta Pattanaik and Kadi Bouatouch, Subsurface Texture Mapping, SIGGRAPH  Sketches

- 2006: Jaroslav Krivanek, Jaakko Konttinen, Kadi Bouatouch, Sumanta Pattanaik, Jiri Zara, Fast Approximation to Spherical Harmonics Rotation, SIGGRAPH  Sketches.

- 2005: P. Gautron, J. Krivànek, K. Bouatouch, S. Pattanaik, Radiance Cache Splatting: A GPU-Friendly Global Illumination Algorithm
SIGGRAPH Sketch, August 

- Journals

- Conferences

- Research Reports

- 2006: P. Gautron, K. Bouatouch, S. Pattanaik, Temporal Radiance Caching, Technical Report no. 1796, IRISA, Rennes, France

- 2006: K. Boulanger, S. Pattanaik, K. Bouatouch, Rendering Grass in Real-Time with Dynamic Light Sources and Shadows, Technical Report no. 1809, July, IRISA, Rennes, France

- 2006: Guillaume François , Sumanta Pattanaik , Kadi Bouatouch , Gaspard Breton, Subsurface Texture Mapping, Technical Report no. 1806, June 2006 / 28 pages.

- 2005: Jaroslav Krivánek, Jaakko Konttinen, Sumanta Pattanaik, Kadi Bouatouch, Fast Approximation to Spherical Harmonic Rotation, Technical Report no. 1728. IRISA, Rennes, France. June.

- 2004: Krivánek Jaroslav, Gautron Pascal, Pattanaik Sumanta, Bouatouch Kadi, Radiance Caching for Efficient Global Illumination Computation , Technical Report no. 1623. IRISA, Rennes, France. June.