Fast Global Illumination Including Specular Effects

1
Fast Global Illumination IncludingSpecular
Effects
2
Motivation

• Realistic Illumination
• All light paths
• Time-Quality Tradeoff
• Interactive Visualisation
• Quality Control

3
Talk overview

• Previous work
• New Integrated Algorithm
• Results
• Conclusion

4
Previous Work

• Deterministic methods
• Radiosity Goral84,Cohen88,etc
• Hierarchy and Clustering Hanrahan91, Smits94,
  Sillion95, etc
• Non diffuse Immel86, Sillion89, Sillion91, etc

• Probabilistic
• Photon Map Jensen96,etc
• Density Estimation Walter97,etc

5
Previous Work

• Multi-pass
• Two-pass Wallace97,Sillion89,etc
• Integrated Chen91,etc

• Interactive viewing
• Render-Cache Walter99
• Directional Storage Stamminger99,etc

6
Overview
D Diffuse and S Non Diffuse

• DD transfer
• Hierarchical Radiosity with Clustering (HRC)

• DSD transfer
• Particle tracing during HRC gather

Images have specular path to eye added by
Ray-Tracing
7
Algorithm Overview

• Construct hierarchy
• Hierarchy elements clusters and surfaces
• For each iteration
• Refine
• Gather - Energy transfer
• particle emission restricted by links
• Push-pull
• particle placement

8
Refinement

• Link placement
• Choose appropriate hierarchy level for transfer
• Refinement test Energy lt e
• Visibility classification and computation
• Shafts and blocker lists for classification/optimi
  sation
• Unoccluded form factor computation

9
Energy transfer through a link

• Diffuse-Diffuse transfer

IRS Radiosity x Form Factor x Visibility
IR IR IRS
10
Energy transfer through links

• Diffuse-Specular transfer

• Diffuse-Specular transfer
• Probabilistic emission of particles
• Reflection on receiver
• Propagation and impact storage
• Links guide particles
• Links encode light flow
• Restrict number of particles

11
Particle Emission

• Number of particles
• Flux S to R/ Constant energy
• Uniform sampling
• Inverse of (Measure(R) x Measure(S))
• Particle power
• Flux from s to r corrected by
• number of particles and
• probability of sample choice

12
Push-Pull

• Push Hierarchy descent
• Particle placement
• Integrate particle power into irradiance
• Radiosity computation on leaves
• Pull Radiosity averaging

13
Particle Placement

• Detect high variation and concentration
• Quantity
• Average position and "Spread Factor"
• Push particle if
• High concentration and high energy

14
Interactive Visualisation

• Computed Solution Diffuse part
• View independant solution
• Hardware rendering
• Ray Trace View dependant part
• Save image
• Interactivity Render - Cache

15
Results Quality control
Vary ?ct parameter
4 sec 1200 particles
5 sec 7800 particles
15 sec 81800 particles
16
Indirect
1 min 42 sec
4 min 34 sec
17
Particle tracing comparison
Complex, indirectly lit scenesimulation ? 10 min
18
Video
VIDEO
19
Conclusion

• Integrated algorithm
• Hierarchical Radiosity with Clustering and
  Particle Tracing
• Handles indirect light well
• Guide particle trace with Links
• Place particles during push-pull
• Rapid computation
• Interactive simulations for small scenes
• Fast coarse solutions for complex scenes

20
Future Work

• Separate Reconstruction
• Low and High frequencies
• Dynamic updates
• Partial particle shooting
• Distributed/Monte-Carlo Ray-trace
• Solution with importance
• Local precise solution
• Detect needed interactions

21
The End