Precomputed Local Radiance Transfer for Real-time Lighting Design
description
Transcript of Precomputed Local Radiance Transfer for Real-time Lighting Design
![Page 1: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/1.jpg)
1
Precomputed Local Radiance Transfer for Real-time Lighting Design
Anders Wang KristensenTomas Akenine-Moller
Henrik Wann JensenSIGGRAPH ‘05
Presented by Shao-Ti Lee2010/04/08
![Page 2: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/2.jpg)
2
OutlineIntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 3: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/3.jpg)
3
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 4: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/4.jpg)
4
IntroductionMAIN IDEA
◦Unstructured light cloud.
![Page 5: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/5.jpg)
5
IntroductionMAIN IDEA
◦Unstructured light cloud.
![Page 6: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/6.jpg)
6
IntroductionFEATURES
◦Local, not distant illumination. Accurately represent incident radiance on
different parts of the model.◦Light positions and intensities are
changeable.◦Lights can be added or removed.◦Materials can be glossy.◦Camera is fully dynamic.◦Scene is assumed to be static.
![Page 7: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/7.jpg)
7
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 8: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/8.jpg)
8
Related WorkPrecompute the exitant radiance
[Wood et al. 2000; Chen et al. 2002]◦Basis: sphere harmonics.
![Page 9: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/9.jpg)
9
Related WorkSphere harmonics.
ApproximatedExitantRadiance
ApproximatedExitant Radiancein the SH basis
SH Basis
![Page 10: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/10.jpg)
10
Related WorkClustered PCA(Principle
Component Analysis) [Sloan et al. 2003]◦For geometry data representation
compression. ClusteringEx. K-Means
PCA
![Page 11: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/11.jpg)
11
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 12: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/12.jpg)
12
Constructing the Light CloudBefore doing this, first divide the
geometry into a set of discrete zones using a simple top-down partitioning algorithm.
![Page 13: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/13.jpg)
13
Constructing the Light CloudUse a two-stage approach to
construct the light cloud.◦Stage 1 Make a sufficiently dense
uniform sampling of the region of interest.
◦Stage 2 The light cloud is then simplified by clustering similar lights using a bottom-up clustering algorithm.
![Page 14: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/14.jpg)
14
Constructing the Light Cloud
This is for point lights.
![Page 15: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/15.jpg)
15
Constructing the Light Cloud
This is for diffuse surface.
![Page 16: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/16.jpg)
16
Constructing the Light CloudA CD E FG H I A B C D E F G H I
Cluster List
Priority queue sorted by △jk
△AB △AD △BD △CE …..
S
S
Compute △SC , △SD , △SE , △SF , △SG ,△SH , △SI and re-sort the priority queue to end a loop and stop until △jk ≧1 for all j, k
B
![Page 17: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/17.jpg)
17
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 18: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/18.jpg)
18
Compressing Surface RadianceBefore compression
◦Per vertex matrix X , with np = nb x nl elements per color channel. nb : The number of SH bases. nl : The number of lights.
After compression using CPCA
ClusterMean
PCA vectors(bases)
weights
![Page 19: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/19.jpg)
19
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 20: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/20.jpg)
20
Real-time RelightingOrganize the local lights in a kd-
tree and locate the m nearest lights.
![Page 21: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/21.jpg)
21
Real-time RelightingTo avoid undesirable popping
effects, set the weight for each pre-computed local light to
After computing all weights, normalization is used. And all weights are multiplied by the power of the light at l.
![Page 22: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/22.jpg)
22
Real-time RelightingVisibility problem
Solution: Use ray tracing with a few rays.
Cannot assign weights!
![Page 23: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/23.jpg)
23
Real-time RelightingDiscontinuity Problem
Suddenly disappear/appeardue to occlusion!
Solution:Smoothly fade out/in lights over time, but that now have become obscured by geometry.
![Page 24: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/24.jpg)
24
Real-time RelightingComputing Exitant Radiance
For each cluster, xm and bi are constant.
![Page 25: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/25.jpg)
25
Real-time RelightingReconstruct the vector of SH
coefficients representing exitant radiance in a vertex program by evaluating
◦Where is the variable to ensure that we get correct blending at the borders between clusters and between zones.
◦Recall that
![Page 26: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/26.jpg)
26
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 27: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/27.jpg)
27
Results
![Page 28: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/28.jpg)
28
Results
![Page 29: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/29.jpg)
29
Results
Left: Method of authors.Right: Ray tracing with per pixel lighting.
![Page 30: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/30.jpg)
30
Results
![Page 31: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/31.jpg)
31
IntroductionRelated WorkConstructing the Light CloudCompressing Surface RadianceReal-time RelightingResultsConclusion
![Page 32: Precomputed Local Radiance Transfer for Real-time Lighting Design](https://reader036.fdocuments.us/reader036/viewer/2022062520/56816172550346895dd0fe38/html5/thumbnails/32.jpg)
32
ConclusionThe system handles indirect
illumination efficiently for models with more than 100,000 triangles.
Future Work◦Soft shadow◦Spotlight