A difference of pronunciation of such phonemes is caused by position of a tongue and mainly by function of vocal cords. Dividing phonemes into groups is a step to make viseme implementation easier. It is sufficient to create one viseme for the whole group of phonemes. For example one such group is formed by phonemes for b , p , m etc. Some phonemes and visemes cannot be assigned to any group.
Vowels are the typical example of such phonemes.
Every vowel has unique phoneme and unique viseme, therefore every vowel needs to have a specific representation. 5.1 Data import System uses VRML model representation. The data of model are described in a prototype based on the IndexedFaceSet node. This node contains all necessary information about polygonal mesh. The prototype contains a few arrays.