diffuse VEX function

Returns the diffuse (Lambertian) illumination given the normalized surface normal.

See also: wirediffuse, Writing a PBR shader

1. vector diffuse(vector nml)

2. vector diffuse(vector nml, vector V, float roughness)

3. bsdf diffuse()

4. bsdf diffuse(vector nml)

See writing a PBR shader for information on BSDFs.

Returns the diffuse (Lambertian) illumination given the normalized surface normal.

The diffuse(vector nml, V; float roughness, ...) form uses the Oren-Nayar lighting model to compute the diffuse illumination for the surface. The Oren-Nayar lighting model is a more sophisticated lighting model than Lambertian lighting. The V vector represents a vector from the surface to the eye (i.e. -normalize(I)). With a roughness of 0, the Oren-Nayar lighting model is equivalent to the Lambertian model. As roughness increases toward 1, the illumination changes to mimic rougher materials (like clay). The Oren-Nayar form of diffuse() is more expensive than Lambertian diffuse lighting.

You can optionally specify a light mask.