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

[Hg200]

Follow-up Comment #5, bug #58956 (project octave):

The answer is probably yes and no. Using min, max for the calculation of xZ1,
xZ2 is most likely motivated by the fact that the projection matrix becomes
​​undefined for a large object distance over a small clipping plane gap.
For example if we remove the min, max statements and enter large xlim, ylim
values, Octave segfaults:

https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/glOrtho.xml

However with this min, max implementation we run into multiple problems: For
example the scene can become invisible. But it is also possible to jam the
renderer if xlim, ylim is chosen unfortunate. The reason for the latter case
is that the difference between the truncated far and near value can become
zero. This is not allowed. Example:

++
daspect ([1, 1, 1]);
xlim ([-1e5, 1e5]);
ylim ([-1e5, 2.46456585e5]);
warning: opengl_renderer: Error 'invalid value' (1281) occurred drawing 'text'
object
--

The attached test code does circumvent the above problems, but as mentioned in
comment #3 it does not solve the displaying issue for larger axis settings. I
guess at this point OpenGl limitations come in.

Comments are welcome.



(file #49697)
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