Technical Animation Pieces 4 — Skinning

Feb.8

Class Summary — Three Techniques of Skinning

LBS Linear Blend Skinning ( = SSD, skeletal subspace deformation)

The logic of LBS is very simple.  Here is a reference I found that explain this method in details: http://graphics.ucsd.edu/courses/cse169_w05/3-Skin.htm

The joints have weight on every vertex, reflecting their impacts. The movement of the vertex will be the blended by the weight.

MIT has developed Pinocchio to show the result of LBS. It first use circles to determine the best position of the skeleton.

LBS has artifacts. One of the biggest problem is the Candy Wrapper Problem, shown below.

[Image]

DQB is one way to solve this problem.

Dual Quaternion Blending

DQB adds the rotation dimensions and interpolate on them. It is not slower than the LBS.

One problem it has is that it can not do extreme things like twist your joint 360 degrees. This problem can be solved by divide the rotation equally into parts and do calculation one by one.

Differential Blending ( Disney)

Cages

Anatomy Transfer ( A good way to think about this problem)

 

 

 

 

Reference website: www.skinning.org

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