** Diffuse reflectance. **

** R = DIFFUSE(Nx,Ny,Nz,S) returns the reflectance for a surface with **

** normal vector components [Nx,Ny,Nz]. S is a three vector that **

** defines the direction to the light source. S can also be a two vector **

** S = [Az,El] specifying the direction with azimuth and elevation. **

** **

** **

** Lambert's Law: R = cos(theta) where theta is the angle between the **

** surface normal and light source. **

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** **

** See also SPECULAR , SURFNORM , SURFL . **

** **