A joint can have parent and child joints. The parent of a joint affects everything it does. The parent’s rotations and translations are all taken into account when computing the current joint’s new position. Using the arm analogy again, the elbow joint would be the parent of the hand joint. Moving the elbow affects the hand. In simple implementations of skeletal animation, each joint has only one parent joint, if it has any at all.
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Ly-l"-1 —^ ‘ lT However, a joint can have many child joints. A child joint is the opposite of a parent joint. Everything you do to the parent joint will filter down into the child joints. Another way to look at this is that the current joint is the parent for all of the joints below it. |
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Figure 5.5 Parent-child joint relationships |