mental ray Architectural and Design Visualization Shader Library

2.5 Detailed Description of Material Parameters 192.5 Detailed Description of Material Parameters2.5.1 Diffusediffuse weight sets the desired level (and diffuse the color) of the diffuse reflectivity. Sincethe material is energy conserving, the actual diffuse level used depends on the reflectivity andtransparency as discussed above.The diffuse component uses the Oren-Nayar shading model. When diffuse roughness is 0.0this is identical to classical Lambertian shading, but with higher values the surface gets a more“powdery” look:Roughness 0.0 (left), 0.5 (middle) and 1.0 (right)2.5.2 Reflections2.5.2.1 Basic FeaturesThe reflectivity and refl color together define level of reflections as well as the intensity ofthe traditional “highlight” (also known as “specular highlight”).This value is the maximum value - the actual value also depends on the angle of the surfaceand come from the BRDF curve. This curve (described in more detail on page 28) allows oneto define a brdf 0 degree refl (for surfaces facing the view) and brdf 90 degree refl (forsurfaces perpendicular to the view).