The light path > shadow ray works for the very reason I mentioned:
It disables shadows for the object that casts the shadow. It can not determine if an object is in the shadow. For a pathtracer shadows are not just the absence of light, but the effect of light being blocked by geometry.
And that’s why the blocking geometry carries information about shadowing, not the object that’s in the shadow because of that…:eyebrowlift2:
Or in Blender Internal terms: The light path > shadow ray can determine if an object is a shadow caster, but not if it is a shadow receiver.
I guess I still don’t completely get it, but that’s ok. I think I understand cycles reasonably well, as it is supposed to be physically based, and I do know something about physics. The hard thing for me to get is that the rays go the wrong way. But blender internal I understand even less. In fact, I have no idea whatsoever of how it works.
Couldn’t you just add in a translucent shader that’s only visible in certain situations? It would help with removing darkness on the back sides of objects.
To clarify on what is exactly “is shadow ray” means:
When sampling lights, Cycles will try and connect a ray (known as a “shadow ray”) from the surface out to the light. If it has a clear shot, the shading point receives light. If not, it doesn’t receive the light and a shadow results. “Is shadow ray” returns 1 only if the shader gets called by a shadow ray. This is also why turning off shadow ray visibility stops an object from casting shadows. If an object can’t be hit by a shadow ray, it can’t stop the light from shining past it.
Theoretically I think you can disabling only self-shadowing in a raytracer by making add an option to stop shadow rays from intersecting the same mesh they took off from. Pretty sure that’s what Arnold is doing here: https://support.solidangle.com/pages/viewpage.action?pageId=1081441
Hey guys, anyone did find a solution for this problem in cycles? It would be great to find a way to disable self-shadowing accepting only other objects shadow. For video compositing (3d on video/image seq) this is essential.
Guys I’v got the solution, well, I hope so. Thanks to a guy, Tayfun Ozdemir, that shared with me this screenshot that helped me to solve the problem. Basically, the result in this case is a monkey with his shadow on the cylinder without the self-shadow of the cylinder in his bottom side.
