[0.21.0] Black artifacts flicker around the Sun

[RacerBG]

Expected Behaviour

These artifacts appeared in version 0.21.0, they were not present in version 0.20.4.

Actual Behaviour

When zooming towards the Sun black artifacts are appearing (flicker).

Steps to reproduce

Zoom towards the Sun.

System

• Stellarium version: <0.21.0>
• Operating system: <Windows 7 SP1 x64>
• Graphics Card: <AMD Radeon R7 250 2GB>
• Screen resolution: <1280x1024>

[gzotti]

There was occasional flicker in previous versions at high zoom. However, I cannot say why.

[alex-w]

Cannot reproduce on linux

[RacerBG]

There was occasional flicker in previous versions at high zoom. However, I cannot say why.

In my case, this started to happen even at moderate zoom.

Also, if this would be helpful I'm running Stellarium in standard mode (without MESA or anything like that).

[alex-w]

OK, I can see artifacts on super zoom when atmosphere is enabled. Rounding issue?

[RacerBG]

OK, I can see artifacts on super zoom when atmosphere is enabled. Rounding issue?

@alex-w I did a quick test - without atmosphere everything is fine.

[gzotti]

OK, I can see artifacts on super zoom when atmosphere is enabled. Rounding issue?

This is what I assumed when I saw it. But where? It is not worrying enough for me to waste a week, sorry.

It is interesting that apparently the atmosphere has the problem, and not the sun (see black polys outside the sun). Or is it during rendering the the corona or flare texture?

[github-actions]

OK, developers can reproduce the issue. Thanks to @RacerBG for the report!

[alex-w]

This is very interesting, but on Mac I can catch the artifacts when I switch rendering of atmosphere (on the high zoom level).

P.S. Effect is more visible near horizon - refraction/extinction issue for very bright object?

P.P.S. Effect on far planets is incredible!

[alex-w]

I can see white artifacts in version 0.20.4 on the mac, so, the source of issue is deeper than we think before... :(

[alex-w]

Apparently the issue was introduced between version 0.13.3 and version 0.14.0, because I cannot see problem in version 0.13.3, but I see it in version 0.14.0.

[gzotti]

What effect do you see for far planets? I can see only occasional dark polys on the sun.

[alex-w]

What effect do you see for far planets? I can see only occasional dark polys on the sun.

In version 0.21.0 I see dark polys on the Sun (see screenshots from Neptune):

[alex-w]

This is interesting: the artefacts are gone when in Skylight dialog the option "Draw Sun after atmosphere..." has been enabled. But this option introducing bug in rendering the solar eclipses, because Moon renders behind the Sun.

[gzotti]

Hmm, yes I tried this mode for an exhibition in 2016 where we did not have a Solar eclipse. These are highly experimental features geared towards auto-shows where some settings may simply be controlled by the storyline.

[RacerBG]

@alex-w Update: With the ShowMySky Visual Model these weird artifacts are gone. They are still present with the default atmosphere but they are not so obvious as they used to be (I need to zoom a lot towards the sun in order to see them).

For reference this is my current configuration:

Stellarium version: <0.23.0>
Operating system: <Windows 7 SP1 x64>
Graphics Card: <AMD Radeon RX 6400 4GB>
Screen resolution: <1920x1080>

[RacerBG]

Update 2: Unfortunately the performance of Stellarium with the ShowMySky Visual Model is about 2 times worse than the standard model even though I upgraded my GPU compared to my original report specs.

[gzotti]

Sure, the ShowMySky is much "heavier" than the old model. There must be reasons for hi-end GPUs...

[alex-w]

The center of Sun is over bright by the fact - I sees it today when atmosphere is disabled...

[gzotti]

That's the "halo" glow texture. If you want, remove when fov is small enough, or do some other trick.

[alex-w]

Hmm... the issue almost is gone in current master (25.0.27)