Hi!
I am working on a modular set consisting of various pieces of walls, floor, ceiling and so on. And the question that stands before me is - how to deal with light bleeding?
I want my walls to be at least 20 cm thick. So I made a “backside” for each mesh.
Like this straight wall piece, for example:
It works fine as a light blocker to prevent bleeding. However, the issue is - when a scene is complete, I want to be able to merge walls, floors and ceiling together for even distribution of light (otherwise baked light can produce seams on separate pieces), and to reduce draw calls. But here’s where a problem arises.
Using Unreal’s merge actor tool, it generates lightmaps automatically based on lightmap channels of merged meshes. And Unreal scales up all UVs to match the same texel density on the lightmap. Meaning the backsides take as much space as significantly more important front sides. Therefore a lot of texture space on the lightmap is wasted for nothing. And I want to avoid that.
Separating meshes from their backsides and importing them as separate props one being a “light blocker” for a specific piece - works. However it makes assembling a scene more tedious for the end user of those modular assets.
And the last thing that I tried - deleting UVs for backside surfaces. This way merge actor tool doesn’t waste any uv space on lightmaps for backside surfaces. However, predictably, it gives an error when exporting meshes like that:
This error occurs when some UVs have almost zero texel density.
So my question is - what would be the best way to approach this? Does this error matters or I can just delete UVs for backsides and don’t think about it?