IRTDO egsr03

Interactive Rendering of Translucent Deformable Objects: 

Interactive Rendering of Translucent Deformable Objects Tom Mertens1, Jan Kautz2, Philippe Bekaert1, Hans-Peter Seidel2, Frank Van Reeth1 1 2

Overview: 

Overview Goal Previous work Translucency model Our method Implementation Discussion, results and future work

Problem: Translucency: 

Problem: Translucency BRDF BSSRDF

Previous work: 

Previous work Jensen et al. (SIGGRAPH ’01): BSSRDF model Jensen et al. (SIGGRAPH ’02): fast, production quality rendering Lensch et al. (PG ’02), Hao et al. (GI ’03), Carr et al. (GHW’03), Sloan et al. (SIGGRAPH’02-’03): interactive, real-time rendering with precomputation Our paper: interactive rendering varying geometry and material (no precomputation)

BSSRDF model: 

BSSRDF model function of distance introduced by Jensen et al. (SIGGRAPH’01) multiple scattering materials with high albedo: marble, milk, wax, skin,…

BSSRDF model: 

BSSRDF model function of distance introduced by Jensen et al. (SIGGRAPH’01) multiple scattering materials with high albedo: marble, milk, wax, skin,…

Integrating the BSSRDF: 

Integrating the BSSRDF hierarchical approach (Jensen et al. ‘02) decouple light and surface sampling, decouple light sampling from geometry 2-pass method: irradiance sampling – integration with octree limitation: rebuilding samples & octree our method integration ~ hierarchical radiosity mesh based: beneficial for geometry updates hierarchy = clustered triangles form factor for BSSRDF: fast local integration

Our Method: 

Our Method boundary element method

Our Method: 

Our Method boundary element method discretized irradiance discretized radiance

Our Method: 

Our Method boundary element method form factor discretized irradiance discretized radiance

example: 

example

sample irradiance: 

sample irradiance

pull irradiance: 

pull irradiance

link roots: 

link roots

subdivide link: 

subdivide link

subdivide link again: 

subdivide link again

gather: 

gather

push: 

push

Hierarchical Evaluation: 

Hierarchical Evaluation hierarchy = clustered triangles tree hierarchy subdivision: 4-to-1 splits face clustering evaluation ~ hierarchical radiosity irradiance sampling + pull construct link hierarchy gather over each link push + average at vertices “oracle” = solid angle interactions at different levels speed advantage

Form Factor:: 

Form Factor: (mid)point to triangle semi-analytical Taylor expansion advantages: fast accurate noiseless indispensable for local integration more distant: 1 sample area integral integral over edges recursive midpoint

Form Factor:: 

Form Factor: point to triangle semi-analytical Taylor expansion advantages: fast accurate noiseless indispensable for local integration more distant: 1 sample

Form Factor:: 

Form Factor: point to triangle semi-analytical Taylor expansion advantages: fast accurate noiseless indispensable for local integration more distant: 1 sample point sampling form factor

Implementation: 

Implementation stored links incremental updates promote/demote links real-time frame rate render on-the-fly instant feedback less memory overhead interactive frame rate irradiance point light (+ shadow) environment map GPU fresnel tone mapping shadow map

Results: 

Results 5-10 fps for 10-20K tris models dual Xeon 2.4Ghz; ATI Radeon 9700 Demo video material change candle twist shadow leak Perlin noise deformation

Discussion: 

Discussion practical technique for interactive applications speed advantage over previous hierarchical algorithm: gathering in higher levels efficient local integration consistent hierarchy after deformation limitation = mesh needs hierarchy limited by resolution fixed topology interactive applications often mesh-based anyway

Future Work: 

Future Work recycle radiosity techniques adaptive meshing, high order interpolation,… improved oracle function varying topology full GPU implementation non-homogeneous media

Acknowledgements: 

Acknowledgements Jens Vorsatz (mesh hierarchies) P. Debevec (light probes) funding: European Regional Development Fund Marie Curie doctoral fellowship