Validation of CG Models - An Introduction to Computer Graphics for Artists - page 133

Fig. 9.22 When face A is made coincident with face B , the polyset C is the result. Polyset C con-
tains individually selectable faces A and B as well as all of their components. Polyset C will not
render properly, but can be fi xed if faces A and B are separated

9.4.3 Coincident Vertices

This is when two or more vertices of the same polyset share identical XYZ coordinate
values (Fig. 9.23 ). Sometimes, if the values are not the same, but are within a very close
tolerance (like .001 of a unit), they are still considered to be coincident. Coincident
vertices can occur when an artist is using a vertex snap to move one or more vertices,
and accidentally puts them in the wrong place. If you have overlapping vertices that
aren't needed for a specifi c purpose, they should be welded together. If they haven't
been, this is considered sloppy because the extra vertices can interfere with texturing,
animation, and lighting as well as creating extra memory demands on your renderer.

9.4.4 Floating Faces

A fl oating face is one or more faces that belong to a polyset but are not connected
directly or by other faces to the main body of the polyset (Fig. 9.24 ). These are a
problem when the fl oating faces become lost in a fi le, usually because they are either
very distant from the main polyset, or they are so small they are diffi cult to fi nd.