PG 2011 Pacific Graphics 2011 The 19th Pacific Conference on Computer Graphics and Applications (Pacific Graphics 2011) will be held on September 21 to 23, 2011 in Kaohsiung, Taiwan. Improving Performance and Accuracy of Local PCA V. Gassenbauer, J. Křivánek, K. Bouatouch, C. Bouville, M. Ribardière University of Rennes 1, France, and Charles University, Czech Republic
Improving P erformance and Accuracy of Local PCA. V. Gassenbauer , J. Křivánek, K. Bouatouch , C. Bouville , M. Ribardière. University of Rennes 1, France, and Charles University, Czech Republic. Objective. Precomputed Radiance Transfer (PRT). - PowerPoint PPT Presentation
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PG 2011Pacific Graphics 2011
The
19th
Pac
ific
Conf
eren
ce o
n Co
mpu
ter G
raph
ics a
nd A
pplic
ation
s (P
acifi
c Gr
aphi
cs 2
011)
will
be
held
on
Sept
embe
r 21
to 2
3, 2
011
in K
aohs
iung
, Tai
wan
.
Improving Performance and Accuracy of Local PCA
V. Gassenbauer, J. Křivánek, K. Bouatouch, C. Bouville, M. Ribardière
University of Rennes 1, France, and Charles University, Czech Republic
Pacific Graphics 2011
2 | 25 Kaohsiung, Taiwan
• Need to compress large data set
ObjectivePrecomputed Radiance
Transfer (PRT)Bidirectional Texture Function
(BTF) compression
Image courtesy of Hongzhi Wu
Pacific Graphics 2011
3 | 25 Kaohsiung, Taiwan
• Relighting as a matrix-vector multiply
• Matrix T(x,ωi) - Billions of elements• Infeasible multiplication• Compression (wavelet, Local PCA)
Precomputed Radiance Transfer
NΜN2N1
3Μ3231
2Μ2221
1Μ1211
TTT
TTTTTTTTT
4
3
2
1
P
PPP
M
2
1
L
LL
Pacific Graphics 2011
4 | 25 Kaohsiung, Taiwan
• Precomputation-based rendering
Related Work
[Sloan et al. 02,03]Low-freq shadows,
inter-reflections
[Xu et al. 08]Dynamic scene,
BRDF editing
[Liu et al. 04], [Huang et al. 10]
High-freq shadows, inter-reflections
• Still use slow and inaccurate LPCA !
Pacific Graphics 2011
5 | 25 Kaohsiung, Taiwan
• BTF compression• [Müller et al. 03], [Filip et al. 09]
• Some heuristic• Farthest first [Hochbaum et al. 85] • Sum based [Hašan et al. 06]• k-means++ [Arthur and Vassil. 07]• …
• Our approach: SortMeans++• Based on k-means++• Faster
Generation of Seeds
Generate seeds
Classification
Update
Until converge
Precompute distances
using ∆-ineq.
Pacific Graphics 2011
19 | 25 Kaohsiung, Taiwan
• Select initial seeds
Our SortMeans++
Select 1st seed at randomTake 2nd seed with probability equal distancesRecluster using ∆-inequalityTake 3rd seed with probability equal distancesRecluster …