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MathGroup Archive 1992

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Graphic problem

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Graphic problem
  • From: wallraff at acds.physik.rwth-aachen.de (Wolfgang Wallraff)
  • Date: Tue, 4 Aug 92 15:32:18 GMT

Currently I am working on a project that deals with displaying ropes as
three-dimensional Graphics in Mathematica. In the past few weeks some problems
occured which I was not able to solve with the original ducumentation!


Problem No.1 :  Displaying 2D-Polygons in 3 Dimension

This Polygon in 2 dimensions display the character "W". (no problem!)

a = {{0.116466, 0.73494}, {0.269076, 0.73494},
{0.353414, 0.353414}, {0.429719, 0.73494},
{0.582329, 0.73494}, {0.662651, 0.345382},
{0.751004, 0.73494}, {0.895582, 0.73494},
{0.742972, 0.176707}, {0.594378, 0.176707},
{0.51004, 0.566265}, {0.421687, 0.176707},
{0.273092, 0.176707},{0.116466, 0.73494}};
Show[Graphics[Polygon[a]]]

Adding a third dimension to the vectors should result in displaying a "W" as a
plane in the 3D-space:

Show[Graphics3D[Polygon[{{0.116466, 0.73494,0}, {0.269076, 0.73494,0},

    {0.353414, 0.353414,0}, {0.429719, 0.73494,0},
    {0.582329, 0.73494,0}, {0.662651, 0.345382,0},
    {0.751004, 0.73494,0}, {0.895582, 0.73494,0},
    {0.742972, 0.176707,0}, {0.594378, 0.176707,0},
    {0.51004, 0.566265,0}, {0.421687, 0.176707,0},
    {0.273092, 0.176707,0},{0.116466, 0.73494,0}}]]]

But it is not displayed in the correct way. It tried the same problem with
numerous other examples, but all Polygons with numerous edges had the same
problem!

Last problem: Memory-requirements of Graphics3D with a large number of
Polygons[]

I am using Mathematica on a Macintosh II ci with 20 MB of RAM. I often get into
memory-problems if I want to display Graphics with a large number of Polygons.
The time for evaluating such graphics becomes long (1 hour or more). For this
kind of evaluation Mathematica needs a lot of memory (20MB seem to be not
enough).
Because of this I would appreciate to get some information about how Mathematica
processes 3D Graphics and how I could display Graphics with a lot of polygons
with limited memory.


Hoping that you can provide answers to my questions

                        Andreas Wallraff

wallraff at acds.physik.rwth-aachen.de  





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