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Re: Bug with 3D graphics lines

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81057] Re: Bug with 3D graphics lines
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sun, 9 Sep 2007 06:19:36 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <fboiim$g91$1@smc.vnet.net>

chuck009 wrote:

> Seems to be a problem with Line when drawing a line in 3D. The following code correctly draws the vertical line from z=0 to z=2:
> 
> line1 = Line[{{0, 0, 0}, {4, 4, 0}}];
> line2 = Line[{{0, 0, 0}, {0, 0, 2}}]
> Show[Graphics3D[{line1, line2}], 
>  PlotRange -> {{-5, 5}, {-5, 5}, {0, 5}}, Axes -> True, 
>  AxesLabel -> {x, y, z}]
> 
> However, when I specify that the line is to be drawn with x and y coordinates not equal to zero, the line is incorrectly drawn:
> 
> line1 = Line[{{0, 0, 0}, {4, 4, 0}}];
> line2 = Line[{{1,1, 0}, {1,1, 2}}]
> Show[Graphics3D[{line1, line2}], 
>  PlotRange -> {{-5, 5}, {-5, 5}, {0, 5}}, Axes -> True, 
>  AxesLabel -> {x, y, z}]
> 
> In 5.2, the lines are drawn correctly.

I guess that by "problem" you mean that the vertical line drawn in the 
second example seems to be jagged. Indeed, it seems to be only an 
artifact of drawing lines in 3D on a 2D support and the perspective 
imposed by the selected view point.

This first document shows what is produced on my Wintel system after 
evaluating both expression and without modifying anything. The second 
vertical line appears to be "broken" more or less in its middle.

http://homepages.nyu.edu/~jmg336/mathematica/line3d1.pdf

Now, this second document shows the same evaluation as before but after 
having played with the mouse on the graphics and change their 
perspectives. We can see (I hope :-) that the second vertical line in 
now straight while the first one is broken in tree parts.

http://homepages.nyu.edu/~jmg336/mathematica/line3d2.pdf

-- 
Jean-Marc


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