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- For very smooth surface, a variety of spline-based surface patch
methods can be used.
- B-splines: [98]
The face is modeled using B-splines. Deformations are performed by
moving groups of controls points.
- Cardinal splines &springs: [138]
A cardinal spline representation is coupled with a spring network.
Muscle deformations are generated by applying forces to the spring
network. For each rest state of the spring network, the spline
surface is recalculated to create discontinuities and bulges:
tangencies are computed to keep the arclength of the spline segment
identical at rest and under compression.
- Hierarchical splines &springs: [143]
The face is modeled using hierarchical splines [49]. Muscles
are defined by forces the definition points of which belong to the
surface: muscle definition follows any face transformation.
Additional effects such as wrinkles are provided by behavior maps.