During sketch development I find that I understand what I would like to 'sculpture' in my design from the section lines I draw as a base, as well as from 'leaving out' areas. However, if you want this to come across to the people making the decisions, you need something that stands out and jumps off the wall in a presentation.
Traditionally I would create presentation sketches by using the base sketch as an underlay, over which I would then draw the clean lines, and would put some marker and pastel on it to to express the 3D form. However, if you did this quickly, it would look too sketchy, and if you did it properly it would actually become an elaborate rendering and be quite time consuming. Another risk would be that in 'cleaning up' the linework, some of the character of the original concept sketch would be lost.
Without trying to take any importance away from traditional art methodologies, these days it is possible to use the original sketch to make quick and eye-catching artwork that not only represents the original raw design ideas to the max, but also does the job of jumping off the wall during a presentation. A good sell.
The following pages show a step-by-step process for quickly creating a presentation rendering...