2012

NOTE Solid objects have meshes and normals correctly oriented, which can be
an aid to creating models for rendering.
When rendering, the renderer searches for all normals that point away from
the viewpoint and removes the associated faces from the scene. This removal
step is called back-face culling and is controlled by the Force 2-Sided option on
the Render Settings palette.
After the back faces have been removed, the renderer uses a Z buffer to compare
relative distances along the Z axis. If the Z buffer indicates that one face
overlaps another, the renderer removes the face that would be hidden.
The time saved is in proportion to the number of faces discarded out of the
total number of faces.
Sometimes you may want to skip the back-face culling step and leave back
faces in (for example, if an object is transparent, if you can see two sides of it
because of its shape and orientation, or if an open object will be rendered
with a view angle that lets you see inside). Transparency also affects whether
one face should hide another. In this situation, make sure Force 2-Sided is
active and all faces are rendered no matter which direction their normal is
pointing.
If you're rendering a drawing that wasn't created with rendering in mind or
if the model was created with another product, you should keep Force 2-Sided
active. This ensures that all surfaces render correctly.
NOTE The rendering performance is only marginally affected when Force 2-Sided
is active.
Every object in a scene is processed by the renderer, even objects that are off
camera and are not going to be present in the rendered view. A model that is
built with the intent of rendering will benefit from good layer management.
2242 | Chapter 46 Render 3D Objects for Realism