bugGNU Octave - Bugs: bug #55224, antialiasing not enabled on...


bug #55224: antialiasing not enabled on multiple Mesa drivers

Submitted by:  Mayeul Cantan <mayeulc>
Submitted on:  Fri 14 Dec 2018 12:59:33 PM UTC  
Category:  Plotting with OpenGL Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Other
Status:  Need Info Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  4.4.1 Operating System:  GNU/Linux

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Thu 28 Feb 2019 09:05:06 AM UTC, comment #2: 

Closing report since the additional info request hasn't been answered.

Pantxo Diribarne <pantxo>
Project Member
Fri 21 Dec 2018 10:10:48 PM UTC, comment #1: 

Thank you for your bug report. I don't have much insight into the graphical portions of Octave, but from what I understand there is no internal driver blacklist.

It appears to me that Octave tries to detect if the OpenGL context supports multisample anti-aliasing and enable it. If not, disable it and fall back to old GL_LINE_SMOOTH anti-aliasing, which may not be supported in modern graphics drivers. This feature test may not be working. For example on my Intel integrated graphics I see that Octave is calling glDisable(GL_MULTISAMPLE).

Do you understand the code better than I do? Can you suggest any changes that might help this situation?

Mike Miller <mtmiller>
Project Administrator
Fri 14 Dec 2018 12:59:33 PM UTC, original submission:  

I did not test with any proprietary drivers, so I do not know if the behaviour is correct sometimes.

On every computer I tried octave on, the following happens:

  • running Octave with `LIBGL_ALWAYS_SOFTWARE=true octave` results in a smooth plot (the one attached as llvmpipe_good.png)
  • running Octave with the hardware-accelerated drivers results in an aliased plot (example attached as i965_bad.png).

The Mesa drivers are otherwise fully OpenGL 4.5-compliant, that I know of, and even allow me to play multiple complex, modern 3D games (native OpenGL titles such as DOOM 2016 and No Man's sky [albeit with OGL 4.5 compatibility profile-enabled mesa such as 18.3.0] play flawlessly).

Is there a reason why antialiasing doesn't work ? This makes the experience substantially worse, especially for first-time users. Maybe some Linux drivers were blacklisted in the past?
In that case, could the blacklisting be lifted for sufficiently advanced Mesa drivers, that support the necessary OpenGL features?

Tested and reproduced on:

  • Arch Linux, R9 Fury (radeonsi), mesa 18.3.1 (OGL 4.5)
  • Arch Linux, i5-7440HQ (i965), mesa 18.3.1 (OGL 4.5)
  • Ubuntu 16.04, i7-4610M (i965), mesa 18.0.5 (OGL 4.5)
  • Ubuntu 18.10, i7-8850H (i965), mesa 18.2.2 (OGL 4.5)

I also hit something along those lines on an older GPU: #53478
I doubt the driver supports the necessary features; a forced fallback to llvmpipe would be appreciated.

I can try to help contributing towards this goal, but would need some guidance.

Mayeul Cantan <mayeulc>


(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

Attached Files
file #45652:  llvmpipe_good.png added by mayeulc (26KiB - image/png - Difference between antialiasing working (Mesa/llvmpipe), and not working (Mesa/i965))
file #45653:  i965_bad.png added by mayeulc (22KiB - image/png - Difference between antialiasing working (Mesa/llvmpipe), and not working (Mesa/i965))


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-02-28 pantxo Open/ClosedOpen => Closed
    2018-12-21 mtmiller StatusNone => Need Info
    2018-12-14 mayeulc Attached File- => Added llvmpipe_good.png, #45652
        Attached File- => Added i965_bad.png, #45653

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