Autodesk AUTOCAD 2006, Command Reference Manual, Page: 1039 / 1490

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.
Gouraud
Calculates light intensity at each vertex and interpolates intermediate
intensities.
Phong
Uses more sophisticated interpolation than Gouraud to generate shading
with more realistic highlights. Phong calculates light intensity at each pixel.
Face Controls
Controls how RENDER treats the faces of 3D solid objects.
Photo Real Render Options Dialog Box
View menu: Render
➤
Preferences
Command line: rpref
Controls rendering options. This dialog box is available when Photo Real is
selected as the Rendering Type and you choose More Options under Rendering
Options in the Rendering Preferences dialog box.
Photo Real Render Options Dialog Box | 1015