A few thoughts:
If you model is detailed enough and you accurately depict a fixture, you can change fixture, bulb and lens color and see the subtle differences in all of the above… which could make or break a fixture budget.
With a rendering you can see the real effects lighting (whether direct or indirect) and shadows have on the space.
Because the models are based on the drawing, the client can see if something will look the way they intended to… long before purchasing anything.
The rendering can be savings investment. This would be less costly than paying for the wrong materials or furniture or even colors later.
Case Study Video
[This will be replaced by the actual video when it is completed]
Watch the Video and learn more about using PhotoRealistic Renderings for Client Presentations
Typical Work Flow
Elijah Bell is an Architectural Designer
You can view more of his work on the CGSociety web site