Validation of CG Models - An Introduction to Computer Graphics for Artists - page 116

Fig. 9.3 Distortion caused by rotation of a face that is connected to another, unmoving face

added to the model. If you have a fl ap on a carton that is connected to another fl ap,
and want both to move appropriately when either is adjusted, you will need to add
animation controls to the fl aps. By adding animation controls, your application will
understand that there is a connection, the nature of the connection, and what behav-
ior results from the connection.
If you cannot add animation controls but want to modify connected faces without
distortion, they will have to be broken free of the polyset they are a part of and
treated separately. When you have fi nished modifying them, they can be rejoined
and coincident vertices merged together.
Distortion is allowed in certain situations, such as during an animation when it is
thought that the movement of the object or camera blur will disguise any distortion.
In other situations, especially in close up shots for theatrical effects, this is not
allowed and should be eliminated if present.

9.2.3 Illegal Texture Boundaries

A texture boundary is a closed group of edges that delineates a face or group of
faces that receive the same texture. An illegal texture boundary is a boundary that
includes faces that should not be included. The result of this is that the texture that
contains too many faces is incorrect and the texture that has lost one or more faces
is also incorrect. This is a likeness error because incorrect texture boundaries
interfere with the clarity of the structure of an object, making it more diffi cult to
understand interior details.