This quick guide covers the best practices how to prepare a project for light baking inside Unreal Engine. As an example, we show a project created in 3Ds Max, which is exported as a .vrscene. The principles outlined in this tutorial are valid for all 3D platforms that can modify UV sets.
The light baking process requires that all objects in the scene must have clean unique UV mapping.
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Light baking a project with neglected UVs have two main consequences:
Extremely slow light baking process;
Producing incorrect results.
That is why, preparing the UV maps upfront is important.
In 3Ds Max, you can select an object and check its UV channel from Tools > Channel Info.
Note that there are channels created by default (marked in red) and channels that you create marked in green.
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V-Ray for Unreal uses the last map channel in the light baking process. Thus, it is important to ensure the last UV channel is set properly. If necessary, create a new channel dedicated specifically for the light map that will be used in the light bake.
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Step 2: Check the UVs
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We have to first check the last available UV channel for problematic UVs such as:
Fancy Bullets
Overlapping UVs
UVs that go outside the 0 - 1 UV space range
If the channel does not contain any of the forementioned issues then this static mesh is suitable for light baking.
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Note that actors that are .vrmesh-es (proxies) when imported in Unreal will excluded from the light baking process but will still contribute to the scene for shadows and GI. With that in mind the vrmesh-es (proxies) does not require to have clean UVs.
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Step 3: Creating new UVs
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If, however, overlapping and/or out the 0-1space range UVs are present then you should create a new UV channel that will be used for the light maps. In the new channel create clean UVs. Do the same procedure for all objects in the scene to ensure a smooth light baking process.
