**System Information**
Operating system: Linux (NixOS)
Graphics card: Intel
**Blender Version**
Broken: 2.91.2
Worked: 2.83.5
**Short description of error**
Smart UV mapping seems to work significantly worse (at least for my test case) since the C rewrite, which landed in 2.91.2.
Before:
{F9837916}
After:
{F9837918}
Test mesh:
{F9837923}
**Exact steps for others to reproduce the error**
Perform Smart UV mapping on the mesh, as detailed in this video: https://www.youtube.com/watch?v=illIxYKb-1k