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UE4 - Is it possible to have two different light map channels for a static mesh? - Please help

synergy11
synergy11
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synergy11 polycounter lvl 6

Hello.

I have grouped two different models that I want to import into UE4 as one piece (One FBX). Each has it's own material ID because one will use a tileable texture and one has a unique texture. My question is I want adequate light map resolution on this model. But it's quite large  and I don't want to have to jack up the Light map resolution really high. I want a separate lightmap channel for each of the pieces.  Is this possible in UE4?

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  • Quack!
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    Quack! polycounter lvl 17
    No I don't believe this is possible right out of the box as there is only 1 choice for which UV channel the lightmap belongs to.  I would assume its 1 lightmap per .uasset, so you would have to figure out a way to bring them in as two different objects, or accept the fact you have to use a higher lightmap resolution.
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  • musashidan
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    musashidan high dynamic range
    Quack is right, you can only reserve a single channel for lightmaps. If you don't want to have to crank up the LM res then you might consider setting the pivots of your  2 meshes up in your 3d software so you can zero the transforms in UE(this will keep their relative world space positions), bring them in as separate static meshes, and create a blueprint of them so they can be treated as a single object. That way you can assign the same material/textures but have separate LM uvs.

    I can't wait till VXGI(or equivalent ) becomes standard in UE so we can finally leave the annoying world of LM's behind us.... :)
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  • synergy11
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    synergy11 polycounter lvl 6

    Ahh thanks folks. This community is great. I never considered the pivot method. Should be ok to deal with once in the editor. I can always group the objects in Ue4 to make moving the two around together easier.  I don't really get why I need to create a blueprint to treat them as a second object ? Is this an optimization thing to reduce the extra draw call of having two objects instead of one?

    Thanks again dudes.

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  • Quack!
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    Quack! polycounter lvl 17
    Grouping them as a BP is just a simple "Make Prefab" step.  There isn't any optimization/reduction unless you call them in the blueprint as Instanced Static Meshes, which comes with another set of limitations.
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  • Obscura
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    Obscura grand marshal polycounter
    Unique lightmaps on instanced static mesh LOD's is unfortunately not supported. At least it wasn't...Not sure about how it is now though.
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