OK, it's my first blog and not sure about protocol so any images are my own...
It seems strange to me that images created with 3d rendering tools are classed as illustrations when, really, we are talking about setting up an image in a very similar way to a photographer in studio, setting up lighting, choosing a lens and taking a picture. The only difference is that the camera, lights and subject are virtual (and "exposure" can take hours :)). Unless we make the models (as above), and, speaking as someone who can't draw a straight line, there is much less illustration involved than, for example, the really impressive work some people can do with photos in photoshop which really are illustrations.
The example below is a model, a "camera", plain white background and 2 lights.
It be interested in having a section within message boards (either in photography or illustrations) for discussion on tools and tricks in modeling and rendering as I'm only at this for a few months and have loads to learn.