[Octave-bug-tracker] [bug #46739] glLineStipple

[Ben Abbott]

URL:
  <http://savannah.gnu.org/bugs/?46739>

                 Summary: glLineStipple
                 Project: GNU Octave
            Submitted by: bpabbott
            Submitted on: Mon 21 Dec 2015 01:32:17 PM EST
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
             Assigned to: None
         Originator Name: Kostas
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

    _______________________________________________________

Details:

Hi

This is about the rendering of dashed and dash-dot lines. With the opengl
plotting system being the default, maybe one could now think about the
rendering quality of lines in plots and prints.

Here there are some -in my opinion- shortcomings of the current situation:

- The gaps in the dashed and dash-dot lines are too large (also compared to
ML's plotting). In my personal octave build I actually replace the "0xF0F0"
mask with "0xF8F8" for dashed and the "020F" mask for dash-dot lines with
"0x27FF".

- The pattern doesn't scale with the linewidth. This makes very thick lines
look strange when combined with some non solid line style.

- The lines have no caps, which makes especially dots look ugly (squares
instead of circles).

- I have just realized that glLineStipple has been deprecated in recent
versions of OpenGL.


Possible solutions:

Soon or later it will probably become necessary to go away from glLineStipple,
so it might be useful to take a look at alternative and higher quality options
already. For example the following work looks very interesting:
https://hal.inria.fr/hal-00907326/file/paper.pdf 

and the code is also available inside a project called gl-agg:
https://github.com/rougier/gl-agg/blob/master/glagg/dash_atlas.py

The following article is also interesting to read:
http://mattdesl.svbtle.com/drawing-lines-is-hard

In any case one would also have to check what is supported by gl2ps.


Unfortunately, I don't see myself having the time to help with the coding of
any new implementation soon but maybe you will find the above information
useful.

Best regards
Kostas




    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?46739>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/