Lambert <-> Oren-Nayar?

[MikeVerta]

I'm learning Arnold 5 by converting my R2-D2 originally done in Maxwell. I have a question: if Base Diffuse Roughness 0=Lambertian, and Diffuse Roughness 1=Oren-Nayar, does that mean that there's a blend between the two models when using values in between? In my Arnold version below, there are some falloff issues I'm working on, and think this is where to look...

[Mike_Farnsworth · Accepted solution]

The Oren-Nayar reflection model has a parameter (mapped to the diffuse roughness) that spans the range between perfect Lambertian diffuse and the more typical flattened results. Arnold only provides the Oren-Nayar model, because it handles the whole range. So yes, you can set your roughness to 0.5 to get an appearance that is in between Lambertian and the more typical flat Oren-Nayar response.