Subdivide algorithm differs from the industry standard #76457
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Reference: blender/blender#76457
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System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.92
Blender Version
Broken: version: 2.90 (sub 0), branch: master, commit date: 2020-05-01 21:55, hash:
83304e4c22Worked: (newest version of Blender that worked as expected)
Short description of error
Blender subdivide algorithm shrinks (smoothes) the model more than the same Catmull-Clark algorithm in other software. This creates problems when importing/exporting models. In version 2.79, the algorithm worked the same way as in other software.
Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]
Added subscriber: @borschberry
Added subscriber: @ankitm
#75632 (Subsurf modifier and multirres modifier give different results when subdivide)
#76302 (Multires Rebuild Subdivision shrinks shape)
Added subscriber: @APEC
to clarify, it since 2.8 version
Added subscriber: @nudelZ
this is not a bug - see https://wiki.blender.org/wiki/Reference/Release_Notes/2.80/Modeling#Subdivision_Surfaces_and_Multires
to "fix" that there should be an option to disable the "limit surface" feature
so blender is especial program with its especial Catmull-Clark algorithm?
Why need to invent bicycles if there is a industry standard algorithm that used in all other 3d apps?
Added subscriber: @moisessalvador
Maybe I'm wrong but I think it's based on OpenSubdiv, which in itself is another standard, so pick your poison. But I agree, I think it should come back as an option, particularly if it gives old performance back
OpenSubdiv it's improved Catmull-Clark in performance (if I understand correctly), so visually you don't see difference.
But we see difference in 2.8 blender.
Need clarification on this.
It would be nice to see such an option. I think this could be fix for this problem as well
Added subscriber: @brecht
Changed status from 'Needs Triage' to: 'Archived'
This is not a topic for the bug tracker in any case, a better place to discuss this is devtalk:
https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests
@brecht I understand that the current algorithm works as planned by the developers. But is it possible that using an inappropriate algorithm that gives an unexpected result is a bug in itself?
It might be a bug according to your definition, but by the definition we employ to decide what is handled in the bug tracker this is not a bug.
Added subscriber: @jeacom
It seems to be trying to approximate the final position of the vertices when infinitely subdivided. Isn't it slower than just subdividing?
Added subscriber: @ckohl_art