Transcript All-Frequency Precomputed Radiance Transfer for Glossy Objects interactive rendering of shadows, both sharp and soft, on non-diffuse objects Xinguo Liu, MSRA Peter-Pike Sloan,

All-Frequency Precomputed Radiance Transfer for Glossy Objects
interactive rendering of shadows, both sharp and soft, on non-diffuse objects
Xinguo Liu, MSRA
Peter-Pike Sloan, DirectX
Harry Shum, MSRA
John Snyder MSR
all-frequency, diffuse
all-frequency, glossy
low-frequency, glossy
lighting=6x32x32 env. map
transfer=1x6144 matrix
lighting=6x32x32 env. map
transfer=10x6144 matrix
lighting=5th order spherical
harmonics (25 coefs)
transfer=25x25 matrix
PRT Formulation
gp (v)  G(v)  (Mp L)
L = lighting coefficients
Mp = transfer matrix (p = surface point)
G(v) = view map (v = view vector)
good accuracy with m=10 – 10D vector
G(v) and 10 rows in matrix Mp
original
m=5, error=10%
m=10, error=2.1%
uses BRDF factorization:
BRDF(v,L )  G(v)  H (L )
PRT Clustering/Compression
divide lighting env. into 16x16 segments
use Clustered Principal Component
Analysis on 24 segments (each 2560D)
like Vector Quantization but uses a linear
subspace (16D) in each cluster
lighting segment 1
lighting segment 2
lighting segment 3