Degenerate Tangent Bases
So I've getting the Degenerate Tangent Bases error on one of my meshes. I got it to not have weird distortion on the texture by generating a light map and changing the light map coordinates to 1. Even after that I'm still getting the degenerate tangent bases bases error. It looks a little strange compared to the rest of the meshes don't have the error but it's not as bad as it was. Now the lighting is showing up weird and there are strange lines going across the mesh in random places. Increasing the light map resolution hasn't worked and I've mucked with a bunch of settings trying to fix it so I'm kind of at a loss as to what to do to get rid of the weirdness.
Also another issue I'm having, that I thought I should mention because I don't know if it has anything to do with this, is that the lighting gets weird after building. Even though the lights are static and the meshes are static and all the meshes have light maps. I'm only using diffuse and spec maps. Not sure if that has anything to do with it.
Its seems to loose some reflectivity, luster, and some light coloring as well, and I have no idea what's causing that.
Any help would be appreciated, I'm kind of at a loss here. Thanks.
asked Oct 18 '14 at 09:22 PM in Rendering
Degenerate Tangents are directly related to your UV and how the mesh is laid out in the UV space.
With 4.7 MikkTSpace was added to the engine.
Here is a simple box with an inset face and extruded center.
Old UE Code:
Basically, the "tangent" vector points in the direction of the U texture coordinate and the "bitangent" (or "binormal" depending who you ask) points in the direction of the V texture coordinate. That coordinate space provides a mapping from "texture space" to "object space" which is what lets tangent space normal mapping work. That's a very simple explanation.
In 4.8 there will be an option to disable this in the Build Settings of the Static Mesh Editor where necessary.
answered May 06 '15 at 02:22 PM
Tim Hobson ♦♦ STAFF
For the reflection and the likes you need a sphere reflection capture. https://docs.unrealengine.com/latest/INT/Resources/ContentExamples/Reflections/1_4/index.html
As for tangents, those look at the first UV, (and can have the worst seams especially for normal maps) so make sure that thats fine. could you show us an image of the uv map for that texture/amterial?
answered Oct 19 '14 at 11:34 AM
I ran into this yesterday as well. In my case there were 2 things that I fixed in the mesh and it went away.
My mesh when imported also looked kind of funny because it was painting the inside face of objects that had a bevel on them. Adding a solidify modifier fixed that.
I hope that helps.
answered May 06 '15 at 11:56 AM
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