lec7 - 1 CS252A, Fall 2010 Computer Vision I Lighting and...

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Unformatted text preview: 1 CS252A, Fall 2010 Computer Vision I Lighting and Photometric Stereo Computer Vision I CSE252A Lecture 7 CS252A, Fall 2010 Computer Vision I Last lecture in a nutshell CS252A, Fall 2010 Computer Vision I Cameras sensor CSE 252A Measured pixel intensity is a function of irradiance integrated over pixels area over a range of wavelengths for some period of time Ideally, its linear to the radiance, but the camera response C(.) may not be linear CSE 252A, Winter 2010 ^ n ( in , in ) ( out , out ) x ; in , in ; out , out ( ) = L o x ; out , out ( ) L i x ; in , in ( ) cos in d Where is sometimes denoted f r . L o x ; out , out ( ) = x ; in , in ; out , out ( ) L i x ; in , in ( ) cos in d CSE 252A, Winter 2010 ^ n ( in , in ) ( out , out ) x ; in , in ; out , out ( ) = L o x ; out , out ( ) L i x ; in , in ( ) cos in d Where is sometimes denoted f r . L o x ; out , out ( ) = x ; in , in ; out , out ( ) L i x ; in , in ( ) cos in d CSE 252A where i =( i , i ) Emitted radiance in direction f r for incident radiance L i . 2 CSE 252A 1. Non-negative: ( in , in ; out , out ) 0 2. Helmholtz Reciprocity Principle: ( in , in ; out , out ) = ( out , out ; in , in ) 3. Total energy leaving a surface must be less than total energy arriving at the surface CSE 252A Lambertian Phong Physics-based Specular [Blinn 1977], [Cook-Torrance 1982], [Ward 1992] Diffuse [Hanrahan, Kreuger 1993] Generalized Lambertian [Oren, Nayar 1995] Thoroughly Pitted Surfaces [Koenderink et al 1999] Phenomenological [Koenderink, Van Doorn 1996] Common Models Arbitrary Reflectance Non-parametric model Anisotropic Non-uniform over surface BRDF Measurement [Dana et al, 1999], [Marschner ] CSE 252A Isotropic BRDF From Hertzmann & Seitz, CVPR03 CSE 252A Anisotropic BRDF From Hertzmann & Seitz, CVPR03 CSE 252A BRDF is a constant called the albedo....
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lec7 - 1 CS252A, Fall 2010 Computer Vision I Lighting and...

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