[Octave-bug-tracker] [bug #47974] Visual differences between gnuplot and OpenGL toolkits

[Dan Sebald]

Follow-up Comment #8, bug #47974 (project octave):

ezmeshc demo:  Well, the issue is pretty simple.  This ezmeshc demo draws a
couple dozen patches after it does the surface/edge construction.  The patches
have a facecolor of "none".  (Why it is doing this, I don't know.)  So, there
is a conflict of multiple graphical objects wanting to set the global
hidden_removal property (i.e., whether "set hidden3d front nooffset" is
applied) differently.

Also, the "hopt" in the surface object has no affect on gnuplot's "with
lines".  I.e., "with lines nohidden3d" never actually disabled hidden3d for
lines, contrary to my understanding.  I went back to the gnuplot code to
verify it has that internal logic, i.e.,


            if (this_plot->plot_style == LINES) {
                this_plot->opt_out_of_hidden3d = FALSE;
            }


So, given that fact, rather than make the default behavior "set hidden3d", in
the attached patch I make the default behavior "unset hidden3d" and the rule
is that the surface and patch can set "set hidden3d", but they can't remove
it.  That is, normally there is no hidden3d behavior, but once it is set it
stays on.  Without the fine control of individually controlling line removal
behavior, this seems like the best that can be done, and it seems consistent
with all the demos


rundemos appearance
rundemos draw
rundemos util


I'm sure it wouldn't take too much to create a plot that causes problems,
e.g., put two surface on the plots--one with hidden behavior and one with
facecolor "none".  I wish gnuplot were a bit more flexible this way (e.g.,
handle hidden removal in groups, true hidden surfaces, etc.), but it would be
quite a while before that arrives.

(file #37243)
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Additional Item Attachment:

File name: octave-gnuplot_patch_hidden_props-djs2016may23.patch Size:2 KB


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