A problem with normal maps exported to UDK.

My models exported to UDK look like this:
Usually I paint textures and other maps manually to avoid texture seams.
With only diffuse texture models in UDK seems to be fine and without any seams, but the problem appears when I add normal or specular maps.
This is how only diffuse map look in blender:

This is with normal map:

This is both diffuse and normal maps after baking:

I export models to .ase, because standart blender .fbx exporter seems to have troubles with exporting smoothing groups.

Things I do:

  1. Create and sculpt high-poly mesh.
  2. Decimate mesh to low-poly.
  3. Create smart uv project.
  4. Paint my textures (and other maps) over the surface.
  5. Bake textures.
  6. Export mesh and textures to UDK.
  7. Making new material for my mesh, linking all maps and saving the package.

UPD: tried to make usual unwrap.
Made another rock from icosphere, marked the seams and unwrapped, then painted the texture and normal map.
Seems fine with and without normal maps:


Also fine in UDK without normal maps:

With normal maps:

I noticed that normals seems to be “turned inside” into mesh on lower side.

Turns out it was wrong texture compression. For normal maps it was supposed to be TC_normalmap, while I was setting default compression for all textures.