Display Ambience 
Turn On or Off the ambient effect (shadow) shown at the edges of occluded faces.
Ambient is a shading and rendering technique that darkens enclosed and sheltered areas within your 3D model without casting sharp shadows, and is used to help with visualization and interpretation.
Display Ambience option deselected
Occluded faces are displayed without shading effect.
Display Ambience option selected
Shading is applied to occluded faces.
