I built Figure 3 from digital photos Hawkes e-mailed me, along with a two-dimensional drawing in AutoCad format. I used AutoCad because until recently I was the analyst in charge of maintaining the computer systems for Pratt & Whitney's Industrial and Marine Division, where I used AutoCad and was thus quite familiar with it. AutoCad currently runs on PCs, whereas Catia for Windows NT will not be released until after the time of this writing. After I completed the model, I knew I could have converted it nicely using the dxf2iv utility, which is available on SGI workstations. Model generation might have been completed with other products, such as the Varkon system on Linux (see Resources), but unfortunately I did not find it until after I had completed the model. One nice thing about Varkon is that the standard shareware version is fully functional, except for limited plotting support, which handles only an HP7475.
Another handy utility available for Linux is Polyred (see Resources). The demo allows you to manipulate a complex VRML model and interactively reduce the number of polygons in it to get a “lighter” model. This is especially useful for slower systems, complex scenes and anywhere interactive response is needed more than visual accuracy. Although the demo program would not allow saving the resulting model, the folks at Systems In Motion (SIM) accepted the above model and reduced it for me to one half and one quarter its original size before sending it back to me. I was impressed with the results.