2nd uv channel doesn't work

Development Rendering
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1

Hello

I have a mesh that makes use of 2 UV channels:

  • Channel 0 - dedicated to color maps
  • Channel 1 - dedicated to a normal map

The imported mesh shows all channels containing valid data:

Channel 0 - color maps

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/UV0.PNG

Channel 1 - a normal map

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/UV1.PNG

Channel 2 - generated lioghtmap coordinates

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/UV2.PNG

I created a simple material that references those channels:

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/Material.PNG

Unfortunately something’s wrong. The model rendered with that material looks flat. The nasty seam running through the middle is a result of how the model was made ( a mirror modifier was used ).
It’s looks as if the normal maps wasn’t taken into account at all.

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/carInUE4.PNG

For comparison, this is how the model looks like in Blender, with the normal map included:

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/carInBlender.PNG

I tried switching off the normal map in Blender, and I got the exact same result as in UE4, that’s why I suspect that the coordinates from the 2nd UV channel are not referenced.
What makes me certain that that’s the root of the problem is that the generated coordinate map preview in the dedicated TexCoord node shows a constant value (0,1) all over:

https://dl.dropboxusercontent.com/u/99282042/secondUVChannelProblem/oddChannelIndexProblem.png

Cna anyone help me explain this mistery? Can UE4 handle meshes with more than 1 UV channel?

Appreciate all the help I can get!

2

Hi ,

Normals are not intended to work with other UV channels without changing some settings with how your material and texture are setup. If you need to have a separate UV for your Diffuse and Normal then it would be better to have the normal map be on UV0 while UV1 is your Diffuse. Typically though the normal and diffuse UV would be the same UV channel.

I hope this helps.

Tim

3

Hm,… Tim any reason why you’d want Normals in UV0 in this particular case?
Ooh wait, thats because it uses the normal tangents (or whatevs its named) from UV0 right?