3D Graphics Programming with QuickDraw 3D 1.5.4
Previous | QD3D Book | Overview | Chapter Contents | Next |
I/O Proxy Display Groups
Description
An I/O proxy display group is used to place distinct specifications of the same model together in a group. The purpose of an I/O proxy display group is to permit a reading application that does not recognize all specifications of a model to pass over those that it does not recognize until it encounters one that it does recognize and can use to recover the model. For example, a pentagon may be represented by either a mesh or a polygon. If both representations are placed together in an I/O proxy display group, then a reading application that recognizes meshes but does not recognize polygons can recover the pentagon from its mesh representation.
Representations of a model in an I/O proxy display group should appear in preferential order: any representation of a model is to be preferred to any other representation of that model occurring later in the group. While drawing, bounding, or picking, the reading application should use the first representation of the model that it recognizes and should ignore all other representations.
Example
BeginGroup ( IOProxyDisplayGroup ( ) )
Polygon ( ... ) # first preference
GeneralPolygon ( ... ) # second preference
Mesh # third preference
EndGroup ( )
© 1997 Apple Computer, Inc.
Previous | QD3D Book | Overview | Chapter Contents | Next |