I've unwrapped UV and set lightmap coordinate index correctly, lightmap resolution is high enough, but object still get black after build light

[VictorCoo]

Thank you guys.

I’m using UE ver 4.10

I’ve played two small project without such problem.

I’ve unwrapped UV and set lightmap coordinate index correctly,

lightmap resolution is high enough, light importance volume have been added,

but object still get black after build light.

This problem has bothered me two days, I still can’t fix it…

Please help me T__T

Here is the file, objec have multiple UV channel, and 4 is the lightmap channel

max:
https://drive.google.com/open?id=0B1jpIDRXp0a-bUV4dDVqS2pKTE0

fbx:
https://drive.google.com/open?id=0B1jpIDRXp0a-clM2RXhqM2FUYm8

[VictorCoo]

I think I’ve found the the temp solution

Error message:

“Warning WallA01 has degenerate tangent bases which will result in incorrect shading.”

Here’s the youtube solution:

It seems like a bug, you just have to leave light map channel to a number that it shoud not...

[VictorCoo]

it’s really weird, I unwrapped light map to channel 1, and set index to 1, then the build result has no problem.

[presto423]

I think this is because the 0 channel is the default for texture UVs. So it’s dark because it’s reading the lightmap UVs through the texture UV channel, which isn’t designed to process / interpolate lighting. Notice also in the screenshot it shows in the error report below that the UVs are wrapping and overlapping, which is how texture UVs are made in some cases, whereas lightmap UVs cannot be overlapping or wrapping past the 0-1 map space.