Random symmetry brush strokes in Weight paint mode
Closed, ResolvedPublic

Description

System Information
Linux Mint Debian Edition on AMD Phenom II x6 1090T, NVidia 460 GTX

Blender Version
Broken: 2.79a RC

Short description of error
Weight paint symmetry makes random stuff See video

Exact steps for others to reproduce the error
Just add a UV Sphere. Subdivide it several times and try to paint weights on it with and without the symmetry activated... random duplicated brush strokes will pop up.

Details

Type
Bug
ronan ducluzeau (zeauro) triaged this task as Incomplete priority.Tue, Feb 13, 6:18 PM

It does not seem to be random.

"Limit Selection to Visible" icon is disabled.
https://docs.blender.org/manual/en/dev/_images/modeling_meshes_selecting_introduction_mode-buttons.png

You are painting through the mesh, faces facing the view and faces at opposite side of the object.
So, with X-mirror option enabled, you are seeing two areas painted.
One just under pointer corresponding to Front faces and the other one corresponding to back side faces under pointer but mirrored on Front side.

Painting through the mesh may be interesting. In master, 2 new options (Front Faces and 2D Falloff) are present and replacing "Limit Selection to Visible" option.
But this change will not be implemented in 2.79a. It will be in 2.8.
It is just a weird behaviour due to the combinaison of 2 features (painting through and symmetry) .
Each one is useful activated individually. But it is not recommanded to activate both at same time.

Feel free to complete the report if you think I missed something.
Precise clearly what steps would correspond to a bug.
Without a reply, report will be closed after a week.

Damn! so that was it! Now I feel dumb as hell