[Octave-bug-tracker] [bug #58956] Empty plot for certain xlim / ylim settings

[Hg200]

Follow-up Comment #30, bug #58956 (project octave):

@mmuetzel: The patch manipulates (double precision) matrices that are passed
to OpenGl, which still performs the actual transformation work, in single
precision. Therefore, even with the patch, we still have this problem of
inaccuracy (see comment #28 the note about "glVertex3d" and
"opengl_renderer::draw_line"). The point was to try to see if the numerical
accuracy (in OpenGL) could be improved by rearranging the coordinate system.
However, this comes at the cost of losing the camera target, which in turn
leads to incompatibilities with Matlab. Since we get no big improvement for
what we lose, please do not use the code. My intention was to just share some
thoughts how we could work (or not work) on the topic.

>From this attempt my conclusion is that we cannot easily fix the problem in
graphics.cc. And btw, even with a newer Opengl API (for example writing into
VBOs) we will still have to deal with this precision problem. IMO regarding
this bugreport the best compromise is your patch in
bug58956_gl_clipping_plains.patch.

So, although not fully fixed, I suggest to close this thread with a link to
the OpenGl collection bug #59418. Maybe we can create a link in bug #59418 to
here.



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