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3D Line Directives Bug?

  • To: mathgroup at
  • Subject: [mg30071] 3D Line Directives Bug?
  • From: "David Park" <djmp at>
  • Date: Thu, 26 Jul 2001 01:20:07 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

Dear MathGroup,

I am obtaining what appears to be a strange bug when drawing 3D straight
lines. I wonder if anyone else has observed similar behavior?

Basically, I am plotting two 3D arrows with polygonal cones at the tips. I
plot a long arrow with a thin black shaft, and afterward plot a shorter
arrow with a thicker colored shaft, which lies along the first arrow. The
directives for the second arrow shaft are lost, so that the shaft comes out
thin and black. This usually, but not always, happens. If I rotate the
second arrow even a smidgen off the first arrow the directives are not loss
and it works properly.

If I have only lines and no polygons anywhere in the plot, the directives
are not loss. But if I have polygons somewhere in the plot, the directives
can get loss. Sometimes the short line has the proper directives for part of
its length.

The behavior will change, but still be incorrect, if I change the Lighting
between True and False. Sometimes the "lost" color directives will be
applied to lines drawn before the directives were set. Once I had to rub my
eyes because the color directives were applied to half of the bounding box

In any case the behavior seems to be associated with putting a shorter line
on top of a longer line and the presence of polygons somewhere in the plot.

David Park
djmp at

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