2008

Geometric primitives have default material identification number assignments,
just as they have default smoothing groups. The default material ID assignment
depends on the type of geometry. Most curved objects such as spheres have
a single material ID. Boxes have six IDs, one for each side. Cylinders have
three: ID number 1 and 2 for the two caps, and ID number 3 for the sides.
Hedra have three: one for each of their P, Q, and R axes.
When you apply a Multi/Sub-Object material, the materials will match the
Multi/Sub-Object material ID numbers to the material ID numbers on the
faces of the object. Faces keep a record of the ID number, and not of the
material name. If the material is anything but Multi/Sub-Object, the material
is assigned to the object's entire surface.
Assigning some defining material ID number to each object before they become
compound object operands can be a useful technique for being able to select
the separate pieces after they're combined.
You can use material IDs for continuous surfaces that require separate paints
or finishes. For example, a car constructed from different types of materials,
such as a colored metal body, chrome parts, glass windows, and so on.
You can use the
Material modifier on page 1445 to assign material ID numbers.
Also you can reassign material IDs using the Editable Mesh > Surface Properties
rollout, or Edit Mesh modifier > Edit Surface rollout.
Glossary | 7843