This feature allows someone to modify the geometry
before Cal3D calculate the bone transformations.
Pre-callbacks is the way like other OpenSource projects
like OpenSceneGraph modify the geometry before the
drawing process. This feature adds more generality and
flexibility to the design.
One file called callback.h is added. This file contains an
interface class that someone who likes to use
pre-callbacks must extend:
updateModel: the method for update the geometry with
getVectorVertex(CalSubmesh *pSubmesh): gets the
VectorVertex buffer that can be modified, for one cal3d
hasPreCallback(CalSubmesh *pSubmesh): checks if one
cal3d submesh has one pre-callback associated.