This command is similar to the ProtoInstance command except that the materials of the prototype are not copied into the current clump. Rather, the new polygons are assigned the current material.
This is useful if your object makes multiple uses of the same group of polygons, but you would like different groups to use different materials (i.e. appear differently). For example, a colorful bunch of balloons could be created by making a single balloon prototype, and then using ProtoInstanceGeometry to instantiate the balloon prototype multiple times each with a different color.
See ProtoBegin for more discussion of prototypes.
<name> the name of the prototype, as declared in a previous ProtoBegin command