Owings Mills--Polytrim

The package used to create this model, polyTRIM, is public domain and available from the Centre for Landscape Research at the University of Toronto. PolyTRIM runs only on Silicon Graphics machines- in this case, an entry-level Indy with 32MB RAM, the 100MHz MIPS CPU, and 24-bit color. The size of this model pushed the hardware very hard (refresh rates of 6-7 seconds were common with all layers on), but polyTRIM's interface allowed for easy control of the displayed level of detail and permitted the handling of a file this size.

The data imported into polyTRIM as .dxf files from autoCAD consisted of contours that had been raised to their altitudes, with all other features 2-D outlines at zero altitude. The ground plane was constructed by automatically triangulating the points on the contours.

Creation of the roads was the most laborious part of the process. The road system was partitioned into several dxf files, so that fewer incorrect triangles would be generated between parallel, close roads. When each file was brought in and triangulated (still in 2-D), extra triangles that were generated had to be deleted: triangulation connects every point in the layer. This editing was facilitated by the various picking features of polyTRIM, especially cross pick.

For more information, please e-mail Dan Ancona at dfa4y@virginia.edu.

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