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Distorted mesh after adding geometry with multires modifier
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Description

FreeBSD 9.2 amd64 GeForce GT520

Broken: master 30-09-2014 c7694b4

This might be a rare edge case but pretty specific. I would describe it as adding geometry to a mesh object that has a multires modifier causes bad geometry when the new geometry is close to or part of faces with flipped normals and multires alterations.

Steps to produce -

  1. With the default cube enter edit mode and flip the normal on one face - Ctrl-Shift-N
  2. In object mode add a multires modifier and subdivide a few times
  3. In sculpt mode move both flipped normal and non-flipped faces
  4. In edit mode add a loop cut
  5. Enter object mode.

If you subdivide the face opposite the flipped normals (step 4) you don't get any distortion, similar with altering more detailed meshes away from flipped faces, the new geometry needs to be part of or adjacent to the flipped normal face/s and the multires reproduction of the new geometry needs to already be moved within the multires data.

Details

Type
Bug

Event Timeline

Shane Ambler (sambler) set Type to Bug.
Shane Ambler (sambler) created this task.
Shane Ambler (sambler) raised the priority of this task from to Needs Triage by Developer.

Will check a bit later this week.

Sergey Sharybin (sergey) triaged this task as Normal priority.Oct 2 2014, 11:25 AM
Sergey Sharybin (sergey) closed this task as Archived.Oct 7 2014, 12:35 PM

Well, things might be improved here for sure, but currently topology changes with multires requires uniform normals. Otherwise interpolaiton might go totally wrong. There might be a trick to improve things without introducing the slowdown, but wouldn't really consider a bug.

We've got some other issues with topology changes and multires. Goes to my personal TODO list, will try to solve later. Thanks for the report anyway.