Generalized Shader IK: Triple jointed IK with directional endpoint

[hai-vr]

Generalized Shader IK is a draft project to create a modified version of the Handholding Shader IK which would have more customization options and would be less specific to dancing. It does not aim to be a superset of the Handholding Shader IK.

The shader code for the Generalized Shader IK is to be kept separate from the Handholding Shader IK: If the Generalized Shader IK were to be implemented within Handholding Shader IK, it would introduce a whole lot of complexity to a piece of very specialized code that is small enough to be simple to understand.

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Currently, the Handholding Shader IK has two joints for which we control the rotation:

• Shoulder to arm
• Elbow to forearm

The end of the forearm, the hand is virtually a joint itself being the target position, but we do not control the rotation of that position.

The shoulder joint is not just a position, it is an orientation. The rotation angles can change based on the orientation of the shoulder, and this is applied on the roll.

The idea would be to implement a strategy so that in addition of the position, we could control a third bone: forearm to hand. Using constraints, we could apply a specific direction to the hand, so that for instance, it would be always parallel to the floor, or to be always lined away from the shoulder.

For instance, this could be used to animate robotic arms with pincers at the end.