Joint constraints are rotational constraints on the
joints of an artificial system. They are used in an
inverse kinematics
In computer animation and robotics, inverse kinematics is the mathematical process of calculating the variable joint parameters needed to place the end of a kinematic chain, such as a robot manipulator or animation character's skeleton, in a g ...
chain, in fields including
3D animation
Animation is a method by which still figures are manipulated to appear as moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Today, most anima ...
or
robotics.
Joint constraints can be implemented in a number of ways, but the most common method is to limit rotation about the X, Y and Z
axis independently. An elbow, for instance, could be represented by limiting rotation on Y and Z axis to 0 degrees, and constraining the X-axis rotation to 130 degrees.
To simulate joint constraints more accurately, dot-products can be used with an independent
axis to repulse the child bones orientation from the unreachable axis. Limiting the orientation of the child bone to a border of
vectors tangent to the surface of the joint, repulsing the child bone away from the border, can also be useful in the precise restriction of shoulder movement.
References
Computer graphics
3D computer graphics
Computational physics
Robot kinematics
Anatomical simulation
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