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Smart UV Project creates overlapping uv-space
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Description

System Information
Windows 8.1 x64
AMD HD 7870

Blender Version
2.75a x64

Short description of error
I am writing a Add-On which procedurally generates a mesh. The mesh can have a lot of spikes. I used Smart UV Project for creating UV-Coordinates and saw that the texture space is sometimes overlapping with another texture space of a different face. I know that I could mark seams manually but I want that the mesh and the UV-Coordinates are created automatically.
I was able to reproduce this with a simple plane.

Exact steps for others to reproduce the error

  1. Create a Plane at x,y,z = 0
  2. Subdivide the Plane two times
  3. Select one vertex and translate it along the z-axis at position greater than 1.
  4. Select the vertex after the next vertex of the already moved vertex (I hope you understand what I mean) and translate it along the z-axis at position greater than 1.
  5. Select the mesh, use smart uv project with angle limit set to 89.00 (FYI: Normally I use 66.00 but the behaviour can be forced with the limit set to 89.00)
  6. In the UV/Image Editor you can see overlapping texture spaces. I think that isn't correct, isn't it? I thought UV Mapping is a one-to-one mapping.

I posted the bug also on blender.stackexchange.org (http://blender.stackexchange.com/questions/34300/smart-uv-project-creates-overlapping-uv-coordinates)

Blend-File:

Event Timeline

Michael Hamburger (Haembi) raised the priority of this task from to 90.
Michael Hamburger (Haembi) updated the task description. (Show Details)
Michael Hamburger (Haembi) edited a custom field.
Campbell Barton (campbellbarton) changed the task status from Unknown Status to Invalid.Jul 27 2015, 4:14 AM

This isn't a bug, in that smart-projection doesn't guarantee no overlapping.

I realize this is a contrived example. and other more subtle cases may still overlap, and it would be nice to detect and correct for this.

However the tool just doesn't support this at the moment.

An alternative is lightmap-pack which ensures no overlap, but won't share UV-vertices.

closing.

I am sorry but that is not a contrived example! I am writing a procedural mesh generator where software agents are moving vertices along their normal. And sometimes two spikes are next to each other.

In the Blender.Stackexchange-Link you can also see a UV Sphere and the error occured there too. And UV Spheres are often used in Low Poly games.