What's Causing This Weird Distortion?

I expected distortion, but . . .

I made a simple 8x8 segments (major & minor radii both 1) torus primitive, default UV, color grid texture. I expect going from the UV squares to this trapezoidal face, all of the squares in it would distort to trapezoids. Instead some of them did, but most distorted to parallelograms, and I’ve no idea why. Help?

DistortionTextureTorus003.blend (503 KB)

That’s a geometric problem! You can add more resolution to the mesh, or have a texture that corrects the distortion.

Remember that every quad is translated to triangles, as it’s what a computer can understand. If the size of the triangles edges in the 3d space varies to a great extend from their size in the UV coordinate system, this is expected to happen.

here’s a similar situation:https://blender.stackexchange.com/questions/3156/how-to-map-a-texture-to-a-distorted-quad

The Subdivision Surface modifier on 3 subdivisions did the trick, thanks!

The UV’s are distorted to be square instead of actual shape of the quadrilaterals, and they cover a large area. It doesn’t use an algorithm that would map the polygon area accurately to match pixels and subpixels on the image. The polygons are also automatically triangulated.

One solution is to increase the geometry resolution enough to have less distortion per face and better approximation of the coordinates. Could also additionally use that higher resolution mesh and bake it back on the original using less distorted UV’s.

Thank you.