Figuring out Translucency Shading when Scattering Dust Tweet

[EJ3d_Art]

I followed Cornelius Dammrich's explanation and SilverWings Youtube video (https://www.youtube.com/watch?v=zMygCctQIFc) on scattering dust but modified it for Blender Octane. Basically, I just created a low poly icosphere and applied the material below to it.

However, there's a problem I came across that seems to only happen in Octane with Blender, where when you scatter the dust on an object (using Octane Material Scatter) the dust partially intersects with the object you're scattering on which creates this weird shading artifact (maybe) where the dust becomes black instead of a partly see through white. This also occurs to the dust object even when it's not being scattered. See the image below where I rendered my scene out and noticed that the dust was black.

After I realised that the reason the dust was being weird was cause of the intersection I figured out a workaround where I just transformed the particles a little bit away from the object I was scattering on. The dust looks really nice now but of course if someone looked close enough they would notice that the dust is actually floating off the object. I'm not entirely sure how they get around this issue when using Cinema4D but I think they have a setting that allows them to delete intersecting particles. It doesn't seem like Blender has the same capability but I'm not sure.

TLDR: I tried adding dust following tutorials for C4D but Blender has a weird shading thing where when particles intersect they become black and glossy instead of white and translucent. I can scale the particles away from the object but then the dust is floating. What's the right way to fix this?

[linograndiotoy]

The best thing you can do in this case would be to create a very simple scene showing the issue. Just create a plane with some dust on it, and please share your scene here so we can take a look.

[EJ3d_Art]

That's the weird thing about this problem, I can't recreate it on a basic plane, the weird black shading only occurs on the grenade.

[TStrolia]

I followed Cornelius Dammrich's explanation and SilverWings Youtube video (https://www.youtube.com/watch?v=zMygCctQIFc) on scattering dust but modified it for Blender Octane. Basically, I just created a low poly icosphere and applied the material below to it.

However, there's a problem I came across that seems to only happen in Octane with Blender, where when you scatter the dust on an object (using Octane Material Scatter) the dust partially intersects with the object you're scattering on which creates this weird shading artifact (maybe) where the dust becomes black instead of a partly see through white. This also occurs to the dust object even when it's not being scattered. See the image below where I rendered my scene out and noticed that the dust was black.

After I realised that the reason the dust was being weird was cause of the intersection I figured out a workaround where I just transformed the particles a little bit away from the object I was scattering on. The dust looks really nice now but of course if someone looked close enough they would notice that the dust is actually floating off the object. I'm not entirely sure how they get around this issue when using Cinema4D but I think they have a setting that allows them to delete intersecting particles. It doesn't seem like Blender has the same capability but I'm not sure.

TLDR: I tried adding dust following tutorials for C4D but Blender has a weird shading thing where when particles intersect they become black and glossy instead of white and translucent. I can scale the particles away from the object but then the dust is floating. What's the right way to fix this?

so, specifically in the blender exporter I have noticed issues with the default ray epsilon in small scenes. By small I mean anything with a detailed view under a meter. You get these sort of warbaly portal like edges with no shadow and a bit of a glossy edge look if it intersects with another object which sounds like what you are mentioning. If you test this now on a plane which has a default scale of 2 meters and dont scale it down for your test then you won't see an issue. IDK for sure that this is what you are experiencing but I have a suspicion. Simple test. and what I do in all my own scenes of that scale is just throw an extra 0 before the 1 in the decimal for the ray epsilon. I usually have mine a 0.000010, instead of 0.000100.

Barring that being it, it could also be your ray depths. I would play with your diffuse and glossy depths where they are >5 bounces. Below 5 bounces may not get you what you need.

Lastly, if you can recreate the issue on a sphere or something and get us scene files that is always a huge help. Try to recreate scene scale and conditions of the problem scene as best as possible. That is the best way for us to help troubleshoot but I also am first in line to say 90% of the time I can't share the original scene for legal reason and can't replicate the problem in a new scene, so I get it if you can't. But, if you can recreate the issue some how, that would be how we can best see the problem. Otherwise it's all speculation on our part.

[EJ3d_Art]

Thank you so much for your reply, I changed the Ray Epsilon like you said and it fixed it so now the dust looks great!
Thanks again for your help, and I'll make sure to attach scene files when I have any other problems .