Instant Radiosity
Alexander KellerUniversity Kaiserslautern
Present by Li-Fong Lin
Outline
• Global Illumination
• Quai-Monte Carlo Integration
• Algorithm
• Extensions
• Reasults
Global Illumination
• Radiance equation :
• Shorthand :
• In the radiosity setting, restricted to only diffuse reflection :
Global Illumination
• Detector functional Ψ: the sum of orthonormal base vectors of a finite vector space.
• Directly select the function below in this paper
Global Illumination
• In realistic applications : ||Tfr|| < 1, less than 100% of the incident radiance is reflected.
• So the Neumann series converges and can be used to solve the integral equation.
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.
van der Corput sequence
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:
Li
PiPi
Pi
y
L(y)
Algorithm
• Only small deviation from mean reflectivity in realistic scene models.
• We can use fractional absorption and avoid Russian Roulette absorption.
• ρN particles will survive after one reflection.
Algorithm
• The Quasi-Random Walk– Evaluate TmnLe using N point lights, TmnTfdLe by using
ρN point lights, and so on.
– Finally the quasi-Monte Carlo integration is performed by accumulating all images with the weight 1/N
Pseudo-Code
Extensions
• Jittered Low Discrepancy Sampling
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.
Results
Results
Results