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Random User Interface Colour Change (2.91+ Regression?)
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Linux-5.10.0-3-amd64-x86_64-with-glibc2.31 64 Bits
Graphics card: RTX 3070 460.56

Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: RTX 3070 461.72

Blender Version:
Broken: 2.91 release, 2.92 release, 2.93.0 Alpha rB70e73974b593 2021-03-10 04:47
Worked: 2.90 and below

Caused by rB7e3967ed37b9 (@Alaska (Alaska) bisected).

Note from @Alaska (Alaska)
Take this bisect with caution. This commit being the cause doesn't line up 100% with recent observations.

Short description of error:
Ever since Blender 2.91 I have experienced this bug where certain aspects of the UI will change colour on occasion. The areas I've seen this issue occur the most are high lighted in the image below.

This flickering seems to occur when two parts of the UI are being updated at the same time? I'm not really sure. The bug seems to occur during a change somewhere in the UI (Clicking on a box, deselecting a bunch of objects, etc), but the same actions don't always trigger this bug. There can even be long stretches of time where this bug does not occur. Hence why I have not reported it, as I've had a hard time finding a reliable way to reproduce it. However, I have found a way to reliably reproduce this issue. It can be done with a third party add-on (shown in the two videos below) or with Blender with factory defaults (as shown in the steps below)

Here's some videos showing off the issue.

This is the area where the bug occurs in the video:

Linux (GPU rendering)Windows (GPU rendering)

I have done three tests (Linux with GPU rendering, Linux with Software Rendering, Windows with GPU rendering) because at first I thought this might be an issue with my Linux installation or the drivers I have. So after testing Linux with GPU rendering, I tested Software Rendering, and that shows the issue, suggesting the issue isn't the GPU driver. Then I tested Windows just to make sure it's not a Linux thing, and seeing the issue show up on Windows shows it's not a Linux thing.

Exact steps for others to reproduce the error:
Unreliable method:

  1. Use Blender for an extended period of time. At some point you may bump into this issue.

Reliable method: (for me at least)

  1. In a new file, change the render engine to Cycles and select GPU compute.
  2. Disable viewport overlays in the 3D viewport.
  3. Split the 3D viewport in two and change one of them to a shader editor
  4. Entered rendered view in the 3D viewport.
  5. Adjust numerical render settings that affect Cycles rendering, causing a viewport refresh. The way you adjust these numbers is you click on it (allowing you to type in a number), then move your mouse to another input field, input a value, and press enter. (In my case, I used AO distance in the Fast GI Approximation section of the Light Paths panel of Render properties).

This change in colour in the UI will be found in the shader editor here:

Here's a video demonstrating it:


Old method: Do not use.

Reliable method (for me - same as videos above):

  1. Install the Scatter add-on by BD3D (https://blendermarket.com/products/scatter). Sorry, it costs money. There are probably other add-ons similar to this one that would allow the easy reproduction of this bug.
  2. Open up a shader editor beside the 3D viewport.
  3. Open the "Properties Panel" in the 3D viewport with N, switch to the Scatter tab and hover your mouse over the Image area and you should see this bug.

Note: I only got the Scatter add-on yesterday (as of the time of writing). I have been experiencing this bug for a few months. The Scatter add-on is not the cause (or I don't believe). During the past few months without the Scatter add-on, I did not have any other add-ons installed (outside of the defaults like Cycles). So I do not believe add-ons are the cause.

Event Timeline

Falk David (filedescriptor) triaged this task as Low priority.Mar 10 2021, 10:42 AM
Falk David (filedescriptor) added projects: User Interface, Restricted Project.

It would be good to have a way of reproducing it without relying on an addon (that is not included with blender). Will mark this as a UI papercut for now.

It would be good to have a way of reproducing it without relying on an addon (that is not included with blender). Will mark this as a UI papercut for now.

I'm sorry I don't have a reliable way that doesn't use an add-on. The bug just seems to occur at random when not using this add-on and I can't figure out why.

As a side note, I decided to bisect the issue and found this commit to be the culprit (from my testing) rB7e3967ed37b9: Gizmo: Navigate: Make use of UI_draw_roundbox_4fv
I have confirmed that this commit is the culprit by testing this commit and the previous commit multiple times and transplanting the affected file from a previous revision of Blender into master (2.93).

This factor of the code being the culprit is also supported by the fact that disabling Gizmos in the 3D viewport resolves this issue, even when using the add-on.

@Falk David (filedescriptor) I believe I have found another way to reproduce the bug. I'm not sure why this way works, but it works for me. Some steps are not necessary, but seem to make it more re-producable.

  1. In a new file, change the render engine to Cycles and select GPU compute.
  2. Disable viewport overlays in the 3D viewport.
  3. Split the 3D viewport in two so you have a shader editior and 3D viewport open side by side.
  4. Entered rendered view in the 3D viewport.
  5. Adjust numerical render settings that affect Cycles rendering, causing a viewport refresh. The way you adjust these numbers is you click on it (allowing you to type in a number), then move your mouse to another input field, input a value, and press enter. (In my case, I used AO distance in the Fast GI Approximation section of the Light Paths panel of Render properties).

This change in colour in the UI will be found in the shader editor here:

Here's a video demonstrating it:

Falk David (filedescriptor) changed the task status from Needs Triage to Confirmed.Apr 14 2021, 4:02 PM

I was able to reproduce this on the latest 2.93.0 Alpha, branch: master, commit date: 2021-04-14 12:25, hash: rBb9207fb43d6f.

Julian Eisel (Severin) raised the priority of this task from Low to Normal.Fri, Apr 23, 1:06 PM
Julian Eisel (Severin) changed the subtype of this task from "Report" to "Bug".
Julian Eisel (Severin) edited projects, added EEVEE & Viewport; removed Restricted Project.

There seem to be multiple ways to trigger this, not just the add-on. It also appeared while testing D8084 and in the asset-browser-poselib branch when selecting poses from the asset view (sidebar), see T87623.

I know I said the bug was initially caused by rB7e3967ed37b9 but some of the stuff I've seen recently doesn't line up with that observation. Maybe I bisected incorrectly or this bug is now occurring in more places due to other commits.

I will look into bisecting again and see what else I can find.

This was caused by rB405a5d3bd7ada5dd5af605b59ba07c7144f144a2.

For reference another way to reproduce the bug as I couldn't use the method from this report.

With this blend file

:

  • Hover your mouse cursor over the toolbar (ensure the tool-bar's scroll-bar is visible).
  • Press Ctrl-Space twice.
  • Notice the top left area switcher draws much darker.

Example video: