Rendering (also visualisation) is the equivalent of product photography, except using virtual models, lights and environments. Normally CAD models are supplied by the client, along with a brief or storyboard and material descriptions. I then convert the CAD models into a format usable by my software and start to light and apply materials to the CAD models.
Why render virtual models? There are several reasons. A client may have a concept CAD model and may want quick, realistic images to use to present to their client. At the other end of the design process, a client may want to use renderings instead of product photography for packaging, because of lead times and for flexibility.
Please have a look at the following projects.