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 Camera’s sensor –CSE 252A • Measured pixel intensity is a function of irradiance integrated over – pixel’s area – over a range of wavelengths – for some period of time • Ideally, it’s linear to the radiance, but the camera response C(.) may not be linear CSE 252A, Winter 2010 ^ n ( θ in , φ in ) ( θ out , φ out ) ρ x ; θ in , φ in ; θ out , φ out ( ) = L o x ; θ out , φ out ( ) L i x ; θ in , φ in ( ) cos θ in d ω Where ρ is sometimes denoted f r . L o x ; θ out , φ out ( ) = ρ x ; θ in , φ in ; θ out , φ out ( ) L i x ; θ in , φ in ( ) cos θ in d ω CSE 252A, Winter 2010 ^ n ( θ in , φ in ) ( θ out , φ out ) ρ x ; θ in , φ in ; θ out , φ out ( ) = L o x ; θ out , φ out ( ) L i x ; θ in , φ in ( ) cos θ in d ω Where ρ is sometimes denoted f r . L o x ; θ out , φ out ( ) = ρ x ; θ in , φ in ; θ out , φ out ( ) L i x ; θ in , φ in ( ) cos θ in d ω –CSE 252A where ω i =( θ i , ϕ i ) Emitted radiance in direction f r for incident radiance L i . 2 –CSE 252A 1. Non-negative: ρ ( θ in , φ in ; θ out , φ out ) ≥ 0 2. Helmholtz Reciprocity Principle: ρ ( θ in , φ in ; θ out , φ out ) = ρ ( θ out , φ out ; θ in , φ 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, CVPR’03 –CSE 252A Anisotropic BRDF From Hertzmann & Seitz, CVPR’03 –CSE 252A • BRDF is a constant called the albedo....
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This note was uploaded on 12/08/2010 for the course CSE 252a taught by Professor Staff during the Fall '08 term at UCSD.

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

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