| Polygon mesh returned by SHADE_VOLUME [message #10918] |
Wed, 04 February 1998 00:00 |
bowman
Messages: 121
Registered: September 1991
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Senior Member |
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I am using the IDL SHADE_VOLUME built-in procedure to find an isosurface
on a 3-D Cartesian grid. According to the documentation, the method used
in SHADE_VOLUME is based on the PolyPaint rendering package developed by
Klemp et al. at NCAR. PolyPaint is described in an American
Meteorological Society Conference Proceedings from 1990.
According to the PolyPaint document, which has a clear, well-illustrate
description of the polygon generation algorithm (based on 'marching
cubes'), PolyPaint will produce one or more polygons for each grid volume
in the data grid. The polygons are not necessarily planar, however, and
they contain up to 7 vertices.
I need to manipulate the polygon mesh, and it is much easier to do if the
polygons are all triangles. The PolyPaint document states that PolyPaint
allows the user to specify the maximum number of vertices in polygons.
Does anyone know whether SHADE_VOLUME has a similar undocumented parameter?
My simple method for making triangles from polygons (Pick a vertex. Draw
lines to each of the other vertices to make triangles.) may not work too
well for some of the more complex, non-planar polygons.
E-mail replies appreciated. Replace the NULL in the e-mail address below
with an 'at' symbol.
Many thanks, Ken Bowman
------------------------------------------------------------ ---------------
Dr. Kenneth P. Bowman, Associate Professor 409-862-4060
Department of Meteorology 409-862-4466 fax
Texas A&M University bowmanNULLcsrp.tamu.edu
College Station, TX 77843-3150 PP-Glider
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