Rounded PT-Like Edges

[RyanB]

@mbullister;415491

Could you post a link to any info about that? I hadn’t heard about that. Back in September Marvin Mittring said he’d like to add the feature, but couldn’t make promises, which is the most recent dev comment I’ve seen. Using masked materials like he suggests in that post wouldn’t work well for edge wear, because you only want to affect the normal of the underlying surface, not its albedo or metalness. Floating geo using a standard material will also interact badly with zdepth and baked lighting.

Using a second set of UVs doesn’t work out of the box, because Unreal always bases its normal information on the first UV channel. Ryan Banks did some shader math to try and correct for this, but never posted his completed graph and the posted shader has problems at triangle edges. Even if it worked perfectly, my opinion is that this would be a worse workflow for artists than geo decals, and would create a large number of mostly-useless unwraps.

The only ideal solution is a deferred/dbuffer decal using geometry created by an artist using modeling tools. This is not currently possible in UE4.

FWIW I posted updated math here: https://forums.unrealengine.com/showthread.php?90684-How-calculate-tangent-vector-for-the-second-uv-channel&p=418481&viewfull=1#post418481

That may work but I agree setting up secondary UVs for meshes like that will be a bit tedious.

Regarding other techniques such as pseudo decals: You can sort of do it but in this case I don’t think it will work very well sadly.

The basic gist behind doing ‘projection’ in a translucent material is to get worldposition behind translucency and use that. But if you wanted the projection to follow the jagged shape of your mesh, you would need some way to encode the center point for each spot along the length of the mesh. This would be something like pivot painter where the information would need to be packed in UVs or something.

But the biggest obstacle with this method, is that you wouldn’t be able to make the decal a “normal only” decal with this method, you would have to rely on doing things like modulating the scene color. While you could compute dot product of the normal and a user-specified light direction, it wouldn’t look the same as actually modifying the normal and it would probably be tricky to deal with.

I think the best bet here is to try and fix the floating and zfighting issues when using the floating masked geo strips. For that you could use camera depth fade (make sure to mark “For Vertex Shader = True”) to lerp between your “near” bias and your “far bias” and then just push the mesh along its own vertex normals. (that means just multiply the distance by the normal and hook to WPO).

It will require a bit of tweaking of the camera fade values and offset values to remove the bugs but I am sure it can be done.

Mesh decals is definitely the way to go for this but it isn’t something easily faked at the moment.