Two and a half D Renderings

Building a 3D model in CAD, and then rendering it in a package like 3D Studio is one sure way to produce accurate, photorealistic renderings. The only drawback is, it takes time. I have put in literally thousands of hours constructing 3D models, and then hundreds more applying the correct materials and lights to bring the models to life. The results are often satisfying, but there are times when some easier alternative is needed.

One way is to generate the computer equivalent of a rendering on paper. Paint programs will do this, but I find the their tools unwieldy. CAD programs like AutoCAD or MicroStation, used in conjunction with presentation software like CorelDRAW or Illustrator, bridge the gap nicely.

Since we're working in 2D here, we must find an image that already shows the subject in perspective: a photograph is perfect. The PCC car image used in the title above started out as a photo I took of an aging, battered PCC 2799 sitting inside Woodland Depot in 1977.
Photo © Mike Szilagyi

The next step is to make a vector-based file out of it. A scanner won't work here, because scanners generate bitmaps, which don't blend well with most CAD packages, especially AutoCAD. The best solution I've found is to tape the photo down to a digitizing tablet, and pick off all the geometry manually. It may well take two hours to digitize a complex photo in this way, but the effort is worthwhile. That said, it often requires many more hours to straighten out all the geometry to the point that it becomes a decent framework for a 2D rendering.
Image © Mike Szilagyi

Once the geometry has been ironed out in the CAD program, it's ready for importing into CorelDRAW. Corel allows any closed line (or pline in the case of AutoCAD) to be filled with a solid color or special fill, at the click of a button. Unlike 3D rendering, each shadow or glint of light on a curved surface must be created manually here. The results can be convincing.
Image © Mike Szilagyi

Like 3D models, 2D renderings based on CAD drawings can be modified rather easily. Paint schemes can be changed, although with fully shaded models, this is not as simple as clicking a button. Structural changes, on the other hand, are much easier than they would be with a 3D model because you can simply rearrange or add 2D geometry. With a 3D model, the new 3D geometry would have to be built, which can be a painstaking process, i.e., a pain.
Image © Mike Szilagyi

Here's another example of a relatively simple modification to existing geometry. Had GM not bought the Philadelphia Transportation Company in 1955, streetcars like this one might not have been scrapped. And had they survived, they may well have looked like this, complete with bus paint scheme, roof-mounted trouble light, and grommetized front windows.
Image © Mike Szilagyi

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