Hi
This one was bugging me for a quite long time. Can anyone help me understand the physical or any difference between 100% rough specular reflection and a 100% diffuse reflection material?
Logically thinking 100% rough specular would be equal to 100% diffuse…but it’s not the case , at least what I’m seeing with arnold shaders…
also, as a side question…why would there be 2 roughness controls (one for diffuse and one for specular) in a shader?
Thank you all
Not it not the same.
100% rough specular still have some rays concentration around reflect vector.
Diffuse itself have no dependency from reflect vector only surface normal.
Think about diffuse like sss with very short radius, short enough to leave hard shadows short not enough to completely randomize incoming ray, until incoming ray direction have no any relation to outcoming(due to 10-100 interreflections).
On other hands reflection component say you about rays with 1-3 intereflection other microgeometry profile, and mostly no interreflections at all, in some cases between neighbore microfacets(this is because sometimes light ray goes back to observeer). But in all cases reflected rays in opposite to diffuse rays strongly depended from incoming rays(concentrate about ideal reflect vector with some distribution dictates brdf rules and depend on roughness and anisotropy).
Yes it confuse some peoples, but diffuse and reflection components have differen nature and not smoothly blend each other other some factor(roughness for example you say).
However some renderers and brdf models make it. maxwell render have this feature, and GGX brdf finaly transform to diffuse.
For some less expierience peoples it simplifies workflow(but actually confuse finaly).
hey, thank you for your reply…though I generally know the technicalities of shaders, and how rays work…this was a bit out of my league…
reflect vector, interreflection…have to research about these
maybe you can direct me to some papers about the topic? i couldnt find anything…it could be in russian or english…or maybe if you can explain it in russian a bit clearer for me I would be grateful.
thank you!