Elastic, Gravity, and Muscle Forces

1. Elastic forces

The simple approach is to treat each degree of freedom (DOF) as a damped spring.   The elastic forces look like this for each DOF:

4 values per DOF, in radians: the min and max for range, and the min and max for the relaxed region. Some joints don't have much of a relaxed region at all - they act like simple springs where any displacement produced a proportional response up the limit possible. Others definitely exhibit a wide range that doesn't cause any spring-back.

Such a simple approach certainly has its drawbacks - for instance, it does a lousy job of handling the irregular range of joints such as the shoulder. However, it's probably valuable to see how far this approach will take us, before moving up to a more complicated scheme. It's probably not a coincidence that other v-human systems, notably Marilyn and DK-96, show significant, visible flaws in their shoulder rotation and placement of upper arm. It's a difficult joint!

2. Gravity

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3. Muscle forces

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