[Octave-bug-tracker] [bug #55224] antialiasing not enabled on multiple Mesa drivers

[Mayeul Cantan]

URL:
  <https://savannah.gnu.org/bugs/?55224>

                 Summary: antialiasing not enabled on multiple Mesa drivers
                 Project: GNU Octave
            Submitted by: 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: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: GNU/Linux

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Details:

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.




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