[Octave-bug-tracker] [bug #45494] Patches have spurious (antialising) lines in vector printout

[Dan Sebald]

Follow-up Comment #30, bug #45494 (project octave):

In an editor, I removed all the black lines from foo.svg.  There are no cracks
or stitching lines visible in Inkscape.  Is it because these are overlapping
triangles?  One has to not reassemble the blue triangle to disrupt the
hidden-surface layering.  But one could, in fact, include the red rectangle as
part of a tessellation with the blue triangles around it.  Nothing is lost in
that case, as this is 2D data and the viewer isn't going to rotate the
surface/view angle.

For gnuplot, breaking up the intersecting shapes into smaller shapes for layer
order is pretty straightforward.  It's more a matter of all the book keeping
that has to be done.  The code is C, so not convenient C++ lists.

BTW, regarding this foo.svg example, zooming into the image in the viewer or
Inkscape shows a bad joining of lines where the red and blue triangles
intercept.  I've attached a screen capture.  Through trial and error I
identified the two lines as these:


<polyline fill="none" stroke="#000000"
stroke-width="0.5" stroke-linecap="butt"
stroke-linejoin="miter" points="298.08,208.44
268.695,384.48"/>
<polyline fill="none" stroke="#000000"
stroke-width="0.5" stroke-linecap="butt"
stroke-linejoin="miter" points="299.721,209.231
74.88,100.786"/>


It looks to me like the x,y-coordinates of the point that is supposed to match
at the intersection of the blue/red triangles at that edge aren't being
computed the same:

298.08,208.44
299.721,209.231


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