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"Sample colour" picks incorrect colour if Mirror modifier exists on mesh
Open, ConfirmedPublic

Description

System Information
Operating system: Ubuntu 18.04
Graphics card: Nvidia Geforce 1080

Blender Version
Broken: 2.80, 0f5b53ba4dc

Short description of error
"Sample colour" picks incorrect colour if Mirror modifier exists on mesh

Exact steps for others to reproduce the error

  1. Open the attached blend file
  2. Press S key to sample the blue colour, and then paint in the red area, and vice versa
  3. Notice it does not paint with the expected colour
  4. "Apply" the Mirror modifier so it no longer exists in the modifier stack
  5. Attempt sampling colours and painting as above, notice it now paints with the expected colour.

Details

Type
Bug

Event Timeline

For developers: after reloading packed Untitled.png image from Image Texture node for it to be shown in 3D View, you take several color samples with "S" key in different parts from the front. You will notice that sometimes the color sampled is the front color (blue) and sometimes the one from the back (red)

Sebastian Parborg (zeddb) triaged this task as Confirmed priority.Thu, Dec 6, 3:30 PM

I can confirm that this is bugged.
If I hold down the S key and hover my mouse over the blue side of the mesh (doesn't matter if it is on the mirrored part or not), I can see that the color picker flickers quickly between red and blue. If I apply the mirror modifier, the color seems to stay solid blue (as it should).

As a work around, I found that I can simply hide the mirror modifier while painting, rather than remove it altogether.