Beast Lightmapping Black Seam Problem

Hi All,

I am getting black lines where objects intersect when baking lightmaps with Beast. Is there any way to avoid this besides combining the meshes? I thought “edge dilation” would do the trick and am using a BeastSettings.xml. To me it appears changing the edge dilation value does nothing at all - is this currently broken? (I’m on Unity 3.5.1 Pro). I also see no changes if I change the bgColor attribute in the same section. What are valid values for that?

The image is baked using no Ambient Occlusion btw. It’s just two hi-poly objects without any textures etc, but they are properly UVed. The seams come from texture interpolation of the dark shadowy parts where objects are intersection. What I basically need would be the light colour to go on for a few pixels - exactly what I though edge dilation would do.

The problem gets worse if I reduce lightmap resolution and the lines get finer if I increase it, but an even higher resolution is not really an option.

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Detecting whether a surface is inside or outside any other mesh is not a simple task. It is possible for convex meshes but much more difficult for arbitrary geometry (and often undecidable in decent computational time).

Your best option is to combine the two meshes into one.

Edit: for references, there have been some work on related issues. Not sure if it has already been integrated in any engine/library.

[rosen08] Seamless Intersection Between Triangle Meshes

Edit2: also found this page (it is for UDK, but can also apply to any engine using lightmapping techniques).