Some black faces after build illumination

The object of the image has black faces after building the ilumination (Production mode).


  • screenshot_1: the black faces of the object
  • screenshot_2: marked seams of UV in Blender
  • screenshot_3: UV Map in Blender
  • screenshot_4: normals
  • screenshot_5: tangents
  • screenshot_6: binormals

Does anyone know why this happens?

I recalculated the Normals and it seems that everything was correct. The problem persist.

Attached screenshot of the lightmap UV of the object. In this UV I can’t see the polygons that are dark in the screenshot_1. But this UV is automatically calculated by UE4 during the import of the FBX.

Thanks for the help!

Yes, the black faces are unwrapped. Attached image of the UV (channel 0) of the object. I marked in red line the polygons of these black faces.

I have created the UV manually from Blender with 0.04 of margin between uvs islands and it looks like it looks better now.

Is a margin of 0.04 sufficient?

If some leaves have dark zones (image attached), because it can be? lightmap resolution too low (64)? margin between uvs islands too low?

I’m trying to optimize the UV lightmap and it’s frustating :frowning:

I think that the UV lightmap has few uvs islands now. But when I build the lighting the object has dark zones. I tested with lightmap resolution to 64, 128 and 256, and the result can be seen in the images :frowning:

screenshot_1: UV lightmap
screenshot_2_64: lightmap resolution 64
screenshot_2_128: lightmap resolution 128
screenshot_2_256: lightmap resolution 256

The size of the texture of the object is 32x32 pixels because it’s a solid color. I tested with a 2048x2048 pixels but the result it’s the same.

I am doing something wrong?

I tested it with 20x and 100x bigger, but the result it’s the same.