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Making changes to your vertex painted sculpt in Sculpt Mode creates rendering artefacts in the colours relative to your camera position
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.50

Blender Version
Broken: version: 2.83 (sub 13), branch: master, commit date: 2020-04-17 20:03, hash: rB76b3aac802f9

Short description of error
While doing some regular testing in 2.83, I noticed that the current vertex painting system does not work nicely with Sculpt Mode. I thought the problem might have been related to Delay Viewport Updates because the bug only appeared when sculpting and undoing/redoing in relation to how zoomed in or out the viewport camera was to the model itself. However, toggling it on and off did nothing, so I am left puzzled.

Exact steps for others to reproduce the error

  1. Take a human sized sculpt of several tens of thousands of vertices and paint it in Vertex Paint Mode.
  1. Switch to Sculpt Mode.
  1. Make any change to your sculpt with the tools available while zoomed in on the model.
  1. Zoom out. The vertex painting artefacts should be fully visible now.
  1. Use undo/redo to activate or deactivate the bug. The bug will disappear when the entire model is visible in the viewport, but appear if you are zoomed in and then you zoom out again.

Event Timeline

Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Needs Information from User.Apr 20 2020, 9:29 AM

Could you please share you .blend file?

Philipp Oeser (lichtwerk) changed the task status from Needs Information from User to Needs Developer to Reproduce.Apr 20 2020, 7:11 PM

Can confirm in this file (having trouble reproducing this from scratch though...)

I can cause glitches when going to material preview and solid shading, I think there is same underlying issue. But I can reproduce this even with files created from scratch.

Philipp Oeser (lichtwerk) changed the task status from Needs Developer to Reproduce to Confirmed.Apr 22 2020, 4:02 PM
Philipp Oeser (lichtwerk) triaged this task as High priority.

T74694, T74622 are also about sculpt drawing glitches.

@Richard Antalik (ISS): if you have a way to repro from scratch: mind putting this in the task description?

@Pablo Dobarro (pablodp606) : mind checking?

@Dalai Felinto (dfelinto): to me, this is a High prio one, feel free to change back...

@Richard Antalik (ISS): if you have a way to repro from scratch: mind putting this in the task description?

I meant that I can cause glitches when going to material preview and solid shading on file created from scratch

  1. Open Blender (glitches are more prominent on fresh run)
  2. Open file
  3. Switch viewport to Material Preview and immediately back to Solid

In some cases it was necessary to repeat step 3.


I have done more investigation on original file, and it seems that issue goes away when you remove other viewports from sculpting workspace. Will do more testing to narrow this down and upload new file if I find "root cause"

Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Bug".May 5 2020, 11:07 AM

In this scenario the 'ac' (active vertex color) of the draw batch that sculpting generates contain uninitialized memory. Perhaps we should add a safeguard to regenerate all VBO.