william a.p. smith and edwin r. hancock department of computer science, university of york, uk cvpr...
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A unified model of specular and diffuse reflectance for rough,
glossy surfacesWilliam A.P. Smith and Edwin R. Hancock
Department of Computer Science, University of York, UK
CVPR 2009Reporter: Annie Lin
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Introduction
1. A unified model of specular and diffuse reflectance from microfacet model by describing both components of reflectance In terms of Fresnel theory and the same model of surface roughness.--- Parameter estimations that all have physical meaning.
2. Reflectance from surfaces1. Surface Roughness model
3. A unified model 1. Masking and shadowing of microfacets2. Fresnel reflectance
4. Specular reflectance5. Diffuse reflectance
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Reflectance from surfaces If the illumination, viewer and normal direction
vectors are specified in global coordinate
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Surface Roughness model
Slope area distribution [7] Torrance and Sparrow Represent the number of facets per unit
surface roughness
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A unified model
The model requires only three physically meaningful parameters: The refractive index of the surface ( ) The surface roughness ( ) The albedo of the surface ( )
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Masking and shadowing of microfacets [5] Oren and Nayar
Fresnel reflectance Fresnel’s equation:
Compute the proportion of light that is secularly reflected form the surface and that which enters the surface and is subsequently diffusely reflected
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Specular reflectance Only those microfacets hose normal vectors lie
within a solid angle dw’ around the vector H , halfway between the light source and viewer , are capable of secularly reflecting light into the solid angle dw, around the view direction vector
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Diffuse reflectance
Radiance from a Lambertian patch
Diffuse radiance from a rough surface composed of shiny microfacets the remaining proportion of the incident light
Account shadowing of the light source and Fresnel transmission into the surface
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Characteristics of the diffuse model
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Experiments The combination model:
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