Instant Radiosity

1
Instant Radiosity

• Alexander Keller
• University Kaiserslautern
• Present by Li-Fong Lin

2
Outline

• Global Illumination
• Quai-Monte Carlo Integration
• Algorithm
• Extensions
• Reasults

3
Global Illumination

• Radiance equation
• Shorthand
• In the radiosity setting, restricted to only
  diffuse reflection

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Global Illumination

• Detector functional ? the sum of orthonormal
  base vectors of a finite vector space.
• Directly select the function below in this paper

5
Global Illumination

• In realistic applications Tfr lt 1, less
  than 100 of the incident radiance is reflected.
• So the Neumann series converges and can be used
  to solve the integral equation.

6
Quasi-Monte Carlo Integration

• Replace the random numbers used in standard Monte
  Carlo with low-discrepancy points.
• Much smoother convergence at a slightly superior
  rate.
• Halton sequence is used in this paper.

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van der Corput sequence
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Algorithm

• Approximate the radiance L in the radiosity
  setting by a discrete density of M point light
  sources.
• The particle approximation yields the very fast
  rendering algorithm

Pi
Pi
Pi
L(y)
Li
y
9
Algorithm

• Only small deviation from mean reflectivity in
  realistic scene models.
• We can use fractional absorption and avoid
  Russian Roulette absorption.
• ?N particles will survive after one reflection.

10
Algorithm

• The Quasi-Random Walk
• Evaluate TmnLe using N point lights, TmnTfdLe by
  using ?N point lights, and so on.
• Finally the quasi-Monte Carlo integration is
  performed by accumulating all images with the
  weight 1/N

11
Pseudo-Code
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Extensions

• Jittered Low Discrepancy Sampling

13
Extensions

• Specular Effects
• By a random decision each surface is tested to be
  specular or diffuse according to its BRDF.
• Mirror the origin ray by the specular surface.
• Realtime Walkthroughs
• In an animated environment, trace fixed length
  paths.
• Keeping the last N images of the last N paths,
  the oldest image is replaced by the new one each
  time .
• Render the global diffuse illumination (only
  direct illumination) into textures, then can be
  displayed interactively.

14
Results
15
Results
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Results