Autodesk AUTOCAD 2006, Command Reference Manual, Page: 1040 / 1490

Anti-Aliasing
Controls the level of anti-aliasing used in rendering.
Back Face Normal Is Negative
Controls which faces are considered back faces in a drawing. When you
draw a 3D face and enter the vertices in a counterclockwise direction, a
positive normal vector points outward toward the viewer and identifies the
face as a front face. The back face is identified by a negative normal vector
that points away from the viewer.
Clearing this option reverses which faces are considered back faces. If Discard
Back Faces is selected, faces with negative normal vectors are considered
back faces and discarded.
Discard Back Faces
Prevents the program from reading the back faces of a 3D solid object when
performing calculations for a rendering (for hidden faces only). This setting
does not eliminate back faces; it only makes them invisible and speeds up
the rendering process.
High
Renders with analytical horizontal anti-aliasing and 16 multiple shading
samples per pixel. The more samples per pixel, the more time it takes to
render the image.
1016 | Chapter 19