1. Toward Real-Time Global Illumination

2. Global Illumination == Offline? Ray Tracing and Radiosity are inherently slow. Speedup possible by: –Brute-force: more hardware, multicore…etc. –Approximate results

3. Under Simplified Assumption Can it become faster if: –…the view is fixed? –…the scene is static? –…the lights are simple? –…if indirect lighting is limited?

4. Lighting Design Assuming: –Static scene –Fixed (or limited) view Example: –Lpics: a hybrid hardware accelerated relighting engine for computer cinematography, SIGGRAPH 2005

5. Lpics Source: http://www.vidimce.org/publications/lpics/pdf/lpics-final-compressed.pdfhttp://www.vidimce.org/publications/lpics/pdf/lpics-final-compressed.pdf

6. Instant Radiosity (and the Problem of Many Lights?) What if we place many virtual light sources to represent indirect lighting? How do we handle a very large number of light sources? –Lightcuts: A Scalable Approach to Illumination, SIGGRAPH 2005

7. Reflective Shadow Maps Dachsbacher and Stamminger. 2005 symposium on Interactive 3D graphics and games (I3D '05). Source: http://dl.acm.org/citation.cfm?doid=1053427.1053460http://dl.acm.org/citation.cfm?doid=1053427.1053460

8. Precomputed Light Transport

9. Indirect Lighting Many indirect lighting effects are subtle, yet crucial for visual realism. Examples are: –Soft shadow –Ambient occlusion

10. Ambient Occlusion Ambient light is a very crude approximation to indirect reflections of surrounding objects. What if a point can’t see much of its surrounding? From: Janne Kontkanen & Samuli Laine ACM I3D 2005

11. Soft Shadow from Environment Lighting Sloan, Kautz, Snyder 2002 Shadows from smooth lighting (precomputed radiance transfer) Sen, Cammarano, Hanrahan, 2003 Shadows from point-lights (shadow maps, volumes)

12. Beyond Monte Carlo Path Tracing? Are global illumination solvers always time consuming? What if the scene and the lights are static ?  Radiosity (view can changes!) What if only the scene is static?

13. Light Stage Take photos under single point light at various positions. Trivial questions: how to produce new images at: –Two point lights? –Area light? –Environment light (captured by light probe)?

15. Precomputed Light Transport Three important papers to start with: –"Precomputed Radiance Transfer for Real-Time Rendering in Dynamic, Low-Frequency Lighting Environments" Sloan et al., SIGGRAPH 2002Precomputed Radiance Transfer for Real-Time Rendering in Dynamic, Low-Frequency Lighting Environments –"All-Frequency Shadows Using Non-linear Wavelet Lighting Approximation" Ng et al., SIGGRAPH 2003.All-Frequency Shadows Using Non-linear Wavelet Lighting Approximation –"Triple Product Wavelet Integrals for All- Frequency Relighting" Ng et al. SIGGRAPH 2004Triple Product Wavelet Integrals for All- Frequency Relighting

16. The following 8 slides are from Ren Ng’s SIGGRAPH 2003 presentation

17. Relighting as Matrix-Vector Multiply

18. Input Lighting (Cubemap Vector) Output Image (Pixel Vector) Transport Matrix

19. Ray-Tracing Matrix Columns

21. Light-Transport Matrix Rows

24. Rasterizing Matrix Rows Pre-computing rows Rasterize visibility hemicubes with graphics hardware Read back pixels and weight by reflection function

25. Low-Frequency vs. All-Frequency Teapot in Grace Cathedral