william a.p. smith and edwin r. hancock department of computer science, university of york, uk cvpr...

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

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

Reflectance from surfaces If the illumination, viewer and normal direction

vectors are specified in global coordinate

Surface Roughness model

Slope area distribution [7] Torrance and Sparrow Represent the number of facets per unit

surface roughness

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 ( )

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

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

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

Characteristics 　　 of the diffuse model

Experiments The combination model: