In v1.5 of PyMOL we introduce ambient occlusion.

Ambient occlusion is a technique that darkens areas of the protein that are occluded. The magnitude of the shading at any given point on the object is determined by how easily light can directly reach that given point. The result is improved sense of depth for images. For example, compare the following two sets of images (left image, no ambient occlusion; right image ambient occlusion enabled):

# enable
set ambient_occlusion_mode, 1

# disable
set ambient_occlusion_mode, 0

# increased hinting, default is 20
set ambient_occlusion_scale, 30

# decreased hinting
set ambient_occlusion_scale, 15