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Surface Association
Determines how the surface components on opposite halves of the skinned object correlate to each other.
Influence Association
Determines how the components that influence the skinned objects (that is, skeleton joints, influence objects, and so on) correlate between the source and destination objects.
The Influence Association occurs in a maximum of two iterations in order to determine the best correlation. You set the Influence Association type for each iteration from a drop-down list beside each level. Set the Influence Association type based on your knowledge of the two skinned objects being compared. As each iteration is completed, the next iteration continues using its specified Influence Association type on any remaining joints. If you are confident that only one iteration is required, you can set the other Influence Association level to None and it will not be occur.
Specifies that no comparison will occur for that level of Influence Association.