The main of the ones listed above is Joints and Bones deformer. This type of deformer is of interest to us due to its hierarchical nature, where the position of a parent (shoulder) drives the child (elbow). This will enable us to easily move whole chunks of Skin by simply rotating the parent joint.
Using only Joint and Bone deformers will never be enough for realistic deformations due to their lack of shape control in areas where the deformation is happening. That is why we must add to our stack of deformers a yet another type to compensate and correct for undesirable transitions: Blend Shapes and Morph Targets.
By binding vertexes to certain joints we are able to move clusters of vertexes around a particular joint. After this stage artists are able to take more control over how areas deform by manual Weight Painting.
Initial transformations and interpolation between vertex clusters usually depend on algorithms that were used to skin or weight vertexes to joint: Quaternion interpolation, Heat Distribution functions, etc...
The Morph Deformer or the Blend Shape is the ultimate one of skin deformers and is used where the total control over the shape of deformation is required.
The Non-Rigid deformer will only get you half way to your desired shape by moving the vertex cluster into the appropriate position, but it will be left up to the artist to sculpt the region further into a Morph Target to produce the desired look.
In some cases Character Riggers use additional modifiers (Cluster Deformers, Sculpt Deformers, Muscle Systems) to push vertex clusters around to help artists up the pipeline to sculpt desired shapes.
The third type of skin deformers and the most computation expensive system of shape control is the Muscle System. This type of deformer brings the most realistic results, due to its ability to slide geometrical skin over underlying muscles.
The way it works is that after placing bones inside the Geometrical skin, the artist needs to correctly and with anatomical accuracy place all muscles which the animal, creature or a human digital double must have in order to replicate the right look.
Anatomy books and other sources of reference material are essential at this stage. It is not that uncommon for sculptors who are really good at this type of work to practice dissecting their neighbour's favourite pets.
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Professional 3D Modeler with 17 years of combined VFX and Games experience, managing Vancouver-based 3D Scanning Studio,
Servicing Visual Effects for Film, Television, Games and Virtual Reality production studios.