Convex Hull drops verts when done on a circle #98306
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Reference: blender/blender#98306
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System Information
Operating system: Windows-10-10.0.22000-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.59
Blender Version
Broken: version: 3.3.0 Alpha, branch: master, commit date: 2022-05-19 21:55, hash:
f600a2aa6d
Worked: (newest version of Blender that worked as expected)
Short description of error
When using the convex hull node on a mesh circle, after 300 points (regardless of the radius) it starts skipping points.
Exact steps for others to reproduce the error
Add a mesh circle, add a convex hull, crank the resolution and check the vertex count
2022-05-21 19-15-43.mp4
Added subscriber: @Erindale
Added subscriber: @mod_moder
I have checked and confirm this.
2022-05-21 22-34-10.mp4
But I suspect this is not a bug. Since floating point numbers are used, this precision seems normal.
Added subscribers: @HDMaster84, @PratikPB2123
Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'
I think so too.
@HDMaster84 , can you comment since you are the original writer of convex hull node ?
This issue is due to the precision of the used numbers. It is exactly the same in the edit mode convex hull.
If you are interested, you can read https://code.google.com/archive/p/bullet/issues/275 which is about the implementation used by blender.
With a circle of say 500 vertices one can expect some vertices to go missing with the convex hull, since the difference in height of the top vertices is (2pi/500)^2/2 = 7e-5 and the resolution of the algorithm is 2/10216=19.6e-5 for a unit circle (which has diameter 2).
Added subscriber: @JacquesLucke
Good find, but yeah, there is probably not much we can do about it given the nature of floating point numbers.