Limiting and damping joint rotation

Limiting rotation angles of joints prevents an articulated limb from bending in an undesirable manner.

1. Select Skeleton -> Joint Tool.
2. Create a set of four joints in a "S" shape in the front view. Hit "Enter" to get out of Joint Tool.
3. Open IK Handle Tool's settings by selecting the small square box next to Skeleton -> IK Handle Tool. Select ikRPsolver as Current Solver.
4. Select the root joint and then the third joint. You should see the line connecting the root and third joint appear. By moving the IK handle up and down, you can see that the "limb" intesect with itself.
5. Select the second joint. Open the attribute editor (Ctrl+A). Click on "Limit Information" tab and "Rotate" tab.
6. Click on the small box next to "Rot Limit Z" to enable the minimum rotation angle. Type -20 into the box under "Min". -20 is now the minimum rotation angle for the joint.
7. Click on the other small box on the same line to enable the maximum rotation angle. Type 70 into the box under "Max". 70 is now the maximum rotation angle for the joint.
8. Move around the IK handle. You can see that the second joint bends within the specified range (-20, 70), while the third joint bends freely.
9. Repeat Steps 5, 6, and 7 with the third joint.
10. Select the second joint. Open "Joint" tab and "Joint Rotation Limit Damping" tab.
11. Let the Z values (values in the third column) of Min Damp Range, Max Damp Range, Min Damp Strength, and Max Damp Strength be 30, 40, 50, and 50 respectively. "Damping Ranges" are values that are relative to the minimum and maximum angles. In this example the damping will be applied to be joint angle between -20 and 10, and between 30 and 70. The Damping Strength should be between 0 and 100. The bigger the strength is, the damping is stronger. 0 does not give any damping effect.
12. Move around the IK handle. You can see that the second joint resists bending or stretching to the limits.