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Can I Disable Light Map UV Generation in ST?

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  • Can I Disable Light Map UV Generation in ST?

    Hi there,

    I'm wondering if its possible to disable light map UV generation in SpeedTree?
    Our project uses dynamic lighting and I'd like to nuke any redundant UV sets for performance reasons.

    Currently I see a few options under the 'Base Tree' properties that deal with lightmap settings, but none to disable light maps.

    Had a look through the docs and couldn't find any info there, perhaps its something simple I'm missing, any info greatly appreciated.

    Thanks.
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  • #2
    Hello,

    Computing lightmap UVs on your tree during export time cannot be disabled. But that doesn't mean you have to use them in-game.

    You didn't mention the format you're exporting or engine you are using, but to cover the major ones... Unity doesn't use our lightmap UVs afaik. UE4 does, but it's not straightforward to remove it, since if you remove all the UVs you will also be removing SpeedTree wind data. You would need to modify the importer to not put lightmap UVs in the VB, and then modify the wind shaders to look at the correct location for wind data, which will have moved. With SpeedTree 9, we'll be moving the lightmap uv to the end so it can be dropped off more easily. With a custom engine, you can of course do whatever you wish.

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    • #3
      Hi Greg,

      Thanks for the quick response.

      Currently we're exporting our assets as '.st' format, and importing into Unreal Engine 4.25.3.
      Its good to know that the lightmap UVs are used for wind, in that case I'll leave them as is.

      Cheers.




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      • #4
        Hi,

        Just to be clear, the lightmap uvs aren't used for wind, but they come before the texcoords we do use for wind in the vertex buffer. So if you remove the lightmap uvs, you'd have to offset everything else in the shader too to keep wind.

        But yeah, it's probably not worth it as an optimization over just optimizing the tree itself. SpeedTree 9 will have a few more routes of optimization in the data and shaders.

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