Nick Pyner, at some time, you'll need to download and install Kerky, yes. I was mistaken on the file type. It is a 3ds, and is one of the options to export from DataCAD, and also one of the options to import into Kerky.
Roger Pingree, what you are wanting to do would be very simple with "Kerky". It's nature is to import anything of a similar color as one "entity" and is difficult to separate in Kerky. DataCAD has 256 colors, so it's pretty easy to make different elements in different colors. If you want early re-bar and later re-bar to be the identical color, just import the later ones into Kerky as a second import, addition to your model. The will remain as separate element and will be easy to leave off until you want them to show.
Kerky is very easy to use, and actually matches your DataCAD colors very well, but it is also very easy to modify the colors any time. After you import your 3ds model from DataCAD, the only thing you really have to add is at least one light. Simply maneuver the model around until what you see is the same position were you want the sun to be shining from and click the "add light" button. You can maneuver the model again and continue to add more light anywhere you want to eliminate dark spots or make shadows to help define the depth of the model. The number of lights probably affects how long it takes to render images, but speed is impressive even with several lights. I usually have a "sun", a couple on backside "fill" lights, and 2 or 3 parking lot lights. Images still render quickly.
When I'm doing my work, I place 8-12 cameras and have Kerky generate 900 images along a path that I merge into a video for a 30-second video. It sometimes takes a couple of hours for that many images. I use another freebie program to make an .avi file from the images.
What you'll be doing, Roger, is putting one camera in position, and then render your image with basic materials, then turn on additional materials, whether re-bar, sill plate, or whatever, render again, turn on more, render again, turn on more, render again, etc. The camera is fixed in place, and can always be returned to in the future, even after saving and reloading, etc. Timewise, these renders are only a few seconds. Kerky will easily do colored surfaces; with a little experimentation, you can make it render bitmaps on surfaces also, like wood grain on studs, etc.
I know your problem; you can't repeat a viewpoint in o2c like you're wanting to do. Kerky will solve that.