Hello,
I am trying to convert a material from a project using legacy shading to use substrate. I’m trying to understand why there is a visual difference between the two, if it is a bug or just an edge case that works differently now. The material is for a misty smoke particle vfx.
Often in vfx when we have billboarded particles, in order to prevent the particle from appearing as if it’s lighting is changing as we walk around it, we use this trick and just force the material normals to be a specific value (in this case worldspace (0,0,1) ). Previously, this worked great, but now using substrate (both the auto-generated conversion, and a slab set up from scratch) there is this odd lighting artifact or something on the material.
First image is legacy rendering. Note how the billboard quad is all a solid color. This is how it should work.
Second image is with substrate enabled. Note how there is now a horizontal line across the quad. That is somehow related to the light direction?
If I change the value in the roughness input, the artifact does visually change, but does not disappear. This makes me believe that is artifact is related to the specular term or is environment reflections or something, even though specular is 0, does that not disable reflections entirely?
Lumen is disabled in the examples but it happens with lumen also. Testing in a fresh project in the basic map. Auto exposure is off, set to manual (11). Bloom and directional light shaft occlusion is all disabled. This is also visible in a scene with nothing but a quad and directional light, but is a bit more subtle. Quad is just a bp with a material billboard.
Is this a technique that just isn’t possible anymore with substrate? Or is there a more correct way to setup the substrate material that I am just doing incorrectly? Happy to supply any extra info if needed.
Thanks!