Light reflection intensity calculation circuit

Abstract

A circuit for calculating a light reflected component with high accuracy. The circuit for calculating a reflected component of light reflected from an object having a rough surface comprises a means for storing the reflectance of an object in relation to the value φ or the value of cos φ, letting a surface normal vector be denoted by a vector N, a light source incidence unit vector be denoted by a vector L, a line-of-sight unit vector be denoted by V, a half vector of the light source incidence vector L and the line-of-sight vector V be denoted by H and defining the inner products as N·L=cos θ, N·V=cos γ, V·H=cos φ, N·H=cos β; a means for storing a luminance distribution in relation to the value of β or the value of cos β; a means for acquiring information on the reflectance term (F 80 (φ)) of the reflected component according to the value of φ or the value of cos φ from the reflectance storing means; a means for acquiring information on the luminance distribution term (D′(β)) of the reflected component according to the value of β or the value of cos β from the luminance distribution storing means; a means for acquiring information on max[0.5 cos θ cos φ, 0.5 cos φ cos γ, cos θ cos β cos γ] which is the maximum value out of 0.5 cos θ cos φ, 0.5 cos φ cos γ, cos θ cos β cos γ; a means for determining the reciprocal of the max[0.5 cos θ cos φ, 0.5 cos φ cos γ, cos θ cos β cos γ] and acquiring information on the geometrical attenuation factor term G′(β,θ,γ,φ) of the reflected component; and a means for acquiring information on the reflected component from the information on the luminance distribution term (D′(β)) and information on the geometrical attenuation factor term G′(β,θ,γ,φ).

1 . A circuit to compute a reflection intensity on rough surface, defining:
 surface normal vector as N, light-source incidence vector as L, view direction vector as V, half-vector between L and V as H, N·L=cos θ, N·V=cos γ, V·H=cos φ, and N·H=cos β, comprising:   a means for storing a reflectance as a function of φ or cos φ;   a means for storing a reflection distribution term as a function of β or cos β;   a means for obtaining a reflectance term (F λ (φ)) from the means for storing reflectance using φ or cos φ as an index;   a means for obtaining a distribution function (D′(β)) from the means for storing a reflection distribution term using β or cos β as an index;   a means for obtaining the value of max[0.5 cos θ cos φ, 0.5 cos φ cos γ, cos θ cos β cos γ], which is a maximum value among 0.5 cos θ cos φ, 0.5 cos φ cos γ and cos θ cos β cos γ;   a means for obtaining a geometrical attenuation factor (G′(β,θ,γ,φ)) of the reflected component by computing a reciprocal of the max[0.5 cos θ cos φ, 0.5 cos φ cos γ, cos θ cos β cos γ]; and   a means for obtaining a reflection intensity using the terms of reflectance (F λ (φ)), reflection distribution function (D′(β)) and geometrical attenuation factor (G′(β,θ,γ,φ)).   
   
   
       2 . A circuit that defines the intensity of reflectance on a rough surface using reflectance, a light reflection distribution function and a light attenuation factor, as a means for obtaining a reflectance component of the reflectance using a reflectance term expressed by the intensity ratio of light incidence and reflection, the distribution function term on the surface of microfacet orientation that is a set of minute surfaces of an object, and a geometrical attenuation factor to express the attenuation on microfacet surfaces that occur as a partial shield of the light incidence and reflection ray, comprising;
 a first means for computing a reflectance term using an inner-product of light-source incidence vector and view vector;   a second means for computing a distribution function by multiplying a half-vector between light-source incidence and a view vector with normal on-object surface;   a third means for selecting a maximum value from multiplied inner-products using surface normal vector, light-source incidence vector, view vector and half vector;   a fourth means for computing a geometrical attenuation factor from reciprocal of said maximum value obtained by the third means; and   a means for obtaining a reflection component by multiplying reflectance term, distribution function factor and geometrical attenuation factor.   
   
   
       3 . A rendering device of light reflection comprising the circuit described in  claim 1 . 
   
   
       4 . A rendering device of light reflection comprising the circuit described in  claim 2 .