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Grass Lightmass Darkening

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    Grass Lightmass Darkening

    I have noticed when grass meshes are placed using the foliage editor they appear darker than when not placed with the foliage editor. That is they appear darker when lightmass is calculated.

    I will not bother adding screenshots, since this, for me anyway, is reproducible with the stock assets in the udk foliage map. Create a new map, paint some grass with the foliage editor and then calculate lightmass. You will see a difference.

    Why is this? Can I stop it doing this?


    Probably because they have shadows


      Im afraid it's not that simple. This is taken from the documentation:

      Each individual mesh instance has its own shadow and/or light map generated by Lightmass, and these are tiled together for each precomputed batch batch can support precomputed. There are several settings on the StaticMesh that should be checked for precomputed lighting to operate well with instanced foliage. Lightmass is less forgiving when generating shadow maps for instanced meshes, and incorrect settings could lead to black meshes after rebuilding lighting.
      The problem is the documentation's suggestions don't work, I and have no idea what setting might help.


        A lot of UE3 games keep foliage/grass as emissive transparent textures. This does limit things a little when dealing with meshes in sunlight vs shadowed areas but thats usually fixed by just making a darker version of the material to match the shadowed areas. Of course this does have its drawbacks because the areas directly on a half shadowed half lit area might looks strange still :P

        If your strictly talking about grass the alternative is to actually model out your grass blades individually instead of doing transparent/masked sheets. The lighting should be better this way and although it creates a lot more polys per mesh, afaik it is still better performance wise because you no longer have to deal with the overdraw that large areas of overlapping transparencies cause.