FBX Static Mesh incorrect blending of tangents.
Unreal is currently blending tangents incorrectly for static meshes. This breaks normal maps that are baked to sync with MikkTSpace, causing ugly seams across the meshes.
Here's a very simple file showing the issue; 3 tris joined together with 1 of the edges (highlighted in the image) having a UV split. All 3 faces share a single smoothing group.
asked Oct 23 '14 at 09:26 PM in Rendering
So the full pull request is up, which fixes MikkTSpace for both static and skeletal meshes. Spencer (JedTheKrampus) and I have tested it with a bunch of meshes and it seems pretty solid.
If this could be tested by the folks at Epic and implemented into the next release, it should help out artists everywhere with a fully synced normal mapping pipeline. Not to mention proper support for mirrored normal maps and improved vertex counts.
Also, if you're running a local fork, could you also test this and let us know if you find any edge cases where things are going wrong? We've not found any yet, but more eyes on it will make certain. Thanks!
answered Nov 03 '14 at 05:52 PM
What you're seeing is the correct intended results.
On the single edge in the center of the picture you can see that there is a single normal along the split edge the in UV. The Tangents also line up with what is expected. There are three on that top point. If we look at the the UV to understand why this is we can see that there are three points that correlate with this as well. The Bottom right and left point and the middle point in the UV space adding up to the three tangents.
Taking that into account we can then look at the vertex count we have which is 7. If we add up the tangents we can see there are a total of 7.
answered Oct 27 '14 at 09:40 PM
Tim Hobson ♦♦ STAFF
The OP has submitted a pull request for this, but it has not been accepted or implemented into the engine. This is marked as resolved until this point for our tracking purposes.
@Farfarer: If your pull request is accepted feel free to post here and I will update accordingly.
answered Oct 28 '14 at 02:52 PM
Tim Hobson ♦♦ STAFF
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