Enumerates drawing modes available in the viewer. More information can be found here.
Shading occurs only in mid-tones so that edge lines and highlights remain visually prominent.
Faces are rendered and lines are not
Conventional smooth lighting values are calculated for each pixel and then quantized to a small number of discrete shades
Lines are rendered and faces are not
Lines and faces are rendered
Selected items are drawn on top, and unselected items are drawn transparent