by Phil_RA » Tue May 22, 2018 1:28 pm
Phil_RA
Tue May 22, 2018 1:28 pm
Hello paride,
This is a specular material with roughness. I used scattering just to see if it made any difference.
My point is, physically speaking, the roughness represents how the microsurface affects the direction in which the light is reflected, so I would expect that it would have a similar impact when light exits the medium than what happens when the ray is reflected as seen with specular reflections. The ray first bounces on the microsurface any number of times, and then into the medium or is reflected from it, but in the former case it means it enters the medium in a different direction than the direction the ray had before bouncing.
So basically, just as specular reflections appear blurred due to roughness, I would expect blurred shadows as well, since the likelihood that a ray will exit in the same direction as the original direction it had before entering the medium would be relative to the surface roughness on entry and exit.
Note I'm not talking about anisotropic scattering, which I don't think any commercial ray-tracing app supports yet anyway. I'm only talking about the result of the surface roughness on the entry/exit.
Again, maybe I'm wrong, or maybe this effect is already happening but is not noticeable enough due to the medium being continuous. I'd be curious to hear a dev on this.
edit: Thinking on it, it would probably just modulate the shadow intensity, not blur it, since the rays are simply being scattered more regardless of proximity to the edges.