Please explain multi-UV map settings for LOD'ed static meshes

I have a static mesh that has 3 LODs, each LOD having 3 UV maps (it’s for mobile, so UV0 is for normal map, UV1 for diffuse and UV2 is for lightmaps).

I don’t quite understand what my Lightmaps settings should look like per LOD.

Each LOD has Lightmap Source and Destination index. By default my mesh LODs all have the same settings - source index is 0 and destination index is 3. What do source and dest. index stand for and what should I set their values to ?

Then there is Lightmap Coordinate Index in the “global” Static Mesh Settings, which is set to 2. What is this and what should it be set to? (I assume index 2 is what UV2 is; in which case it’s the correct value)

How do Lightmap Source and Destination index, and Lightmap Coordinate Index relate to each other ?

Thanks beforehand

No one? :frowning:

source index is where UE4 gets its UV information for making a lightmap UV. The destination index is where it puts its own generated UVs. the lightmap coordinate index is the index that lightmass uses for baking the lightmaps. consider it the UV channel for lightmaps. The coordinate index should be the same as the destination index.
an example:
For a basic mesh where you have 1 uv set for your texture, the source should be index 0 (the first channel, ie the only channel with any UV information), and the destination should be 1 (the second uv channel, ie the next free channel). the lightmap index will then be 1 also.
For you, the source should be 2 and the destination should be 2 and the index should be 2, so that UE4 uses your pre-made lightmap UVs and improves them (adding the right amount of padding, etc…) and bakes that back on to the same UV channel, then uses that for the lightmaps.

also you only waited like what, 4-5 hours for a response? Rude.

Thanks a bunch! No wonder my lighting never looked right :confused:

Sorry if I made you feel that way. Although I don’t believe I was rude. Impatient maybe, not rude :slight_smile: And I waited for more like 15+ hrs. Really was hoping for Epic to chime in and also put this info into the docs, where it should have been since long time ago :confused: I guess even folks who suppose to keep docs up-to-date work on Paragon too.


I think Src/Dst index is for UE4 to generate lightmaps - it doesn’t seem to have any effect on lighting (just tried changing it and rebuilding lighting) :confused: Lightmap Coordinate Index on the other hand does.

EDIT: I take it back - after setting src/dst index to 2, I still have proper lighting in PIE, but on the device my meshes are pitch black :confused: