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How do i correctly generate or create a Lightmap for a very complex object?

I'm unwrapping a building that has a lot of layers (every wall will be separated multiple times [image of one story: http://puu.sh/cKOlN/6a21310459.png ), and all walls will (and have to) be merged into a single object.

If i use my own UV map it will have overlapping UV's and that wouldn't work.

As soon as i generate a Lightmap, some faces show up a very dark grey, even though they have their own space. [img: http://puu.sh/cKOCm/1e3b84c7b5.png ] So i assume that those UVs don't have enough space for shading. How would i go about making correct lightmaps for an object this complex? Is it possible to use multiple ( like 5-6 ) lightmaps for a single object just to separate the UVs a bit?

I realise the UV map is very bad at the moment, but i want to clear up these problems before i run into more problems later on and having to re-do a lot of time. [image of my unwrap : http://puu.sh/cKP7X/bf47040b24.png ] [image of auto unwrap : http://puu.sh/cKP9W/e619cd2a3e.png ] [images of UE4 Details Settings: http://puu.sh/cKPdb/25d74f1589.png , http://puu.sh/cKPep/36dc305e5b.png ]

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asked Nov 10 '14 at 10:21 AM in Everything Else

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instead of separating every uv face, stitch more of the UV faces into fewer, larger islands so you can have less space wasted on padding. pad in between objects to avoid bleeding, but don't pad around the edges of the lightmap, because that padding will be automatically generated. instead of treating the whole building as a single object, separate it into many different objects, so they each get their own lightmap. also you should snap lightmap UVs to the nearest pixel to avoid baking problems.

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answered Nov 10 '14 at 11:32 AM

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avatar image moremagical Nov 10 '14 at 12:41 PM

Since not every wall is made per room ( img: http://puu.sh/cKUT4/b3fea0fc88.png ) would that give any problems in the lightmap, and would i have to make every wall specifically per room so the inner walls' lighting has no weird lines or hard edges? i'm trying cluster the UV faces up correctly now but this has been bugging me.. Thanks for responding so quickly!

avatar image moremagical Nov 10 '14 at 03:44 PM

I have tried making the UVs a bit better [UV Img: http://puu.sh/cL3BH/7c3e1b7077.png ] but the result is not much better than before [img: http://puu.sh/cL3Av/4e7e1416e7.png ] Lightmap res is 128, so already pretty high.

Is there something i'm doing wrong, or that i should change?

avatar image ScottSpadea Nov 11 '14 at 08:41 AM

having a low lightmap resolution is more important for objects that will be instanced around the scene, since every instance will need a unique lightmap, it adds up quickly. but you have a very large unique asset, so you can make the lightmap larger if you need to.

the dark areas above the doorways are not from low res lightmaps, they are artifacts from texture bleeding. to avoid texture bleeding, separate your uv islands any time a dark edge is next to a light edge, usually around sharp corners, and make sure your verts are snapped to the pixel grid properly.

lightmaps automatically get extra padding around the edges, so subtract 2 pixels from the resolution to get the proper grid snapping size. for a 64 res lightmap, you should be snapping to a 62 X 62 grid. for a 128 lightmap, you should snap to a 126 x 126 grid.

any bottom faces or faces inside of walls can be scaled down and grouped together without padding, because no one will see it. inside of door ways should be ripped into individual faces with padding around them. flat walls and smooth shapes should be as contiguous as possible.

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You should split it into modular sections if you want really high quality light map.

Otherwise your only option left is to manually unwrap light map and use very high resolution for light map baking.

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answered Nov 10 '14 at 11:19 AM

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