Eurographics 2011 LLHNDLJDNO LK Our SPMM A Sparse Parametric Mixture Model for a genera/bte Compact Easily editable Can be efficiently rendered
Our SPMM • A Sparse Parametric Mixture Model for a general BTF: – Compact – Easily editable – Can be efficiently rendered
Eurographics 2011 LLHNDLJDNO LK Our SPMM A sparse linear combination of rotated analytical BRDES weights parametrIc functions function b(0,O)(x:0)=∑ap1(0,0)+er(0,0) where Pi(0i, 00)=f (Kj, R(Oi), R(Oo)(nj 01) rotated brde Use 7 popular models Lambertian Oren-Nayar, Blinn-Phong, Ward, Cook-Torrence Lafortune and ashikmin-Shirley
• A sparse linear combination of rotated analytical BRDFs Our SPMM where weights parametric functions residual function rotated BRDF Use 7 popular models: Lambertian, Oren-Nayar, Blinn-Phong, Ward, Cook-Torrence, Lafortune and Ashikmin-Shirley
Eurographics 2011 LLHNDLJDNO LK Our SPMM An example normal Lam bertin Cook-Torrance Lafortune BTF Q+ Lambertian Residua
Our SPMM • An example
Eurographics 2011 LLHNDLJDNO LK Fitting algorithm Challenges for fitting SPMm to a bte. Need to determine The number of brdfs The types of brdfs Non-linear parameters for each BrdF Corresponding weights
Fitting Algorithm • Challenges for fitting SPMM to a BTF. Need to determine: – The number of BRDFs – The types of BRDFs – Non-linear parameters for each BRDF – Corresponding weights
Eurographics 2011 LLHNDLJDNO LK Fitting algorithm Existing BRDF fitting algorithms cannot be used e.g. Levenberg-Marquardt Fits fixed num ber of lobes Unstable and expensive for more than 3 lobes Does not fit rotated brdes No way to control sparsity
Fitting Algorithm • Existing BRDF fitting algorithms cannot be used – e.g. Levenberg-Marquardt • Fits fixed number of lobes • Unstable and expensive for more than 3 lobes • Does not fit rotated BRDFs • No way to control sparsity