Even with carefully defined joint precedence and joint parameters there are many valid IK solutions for any placement of an end effector. You set position and rotation thresholds to control IK precision and solution speed.

• The threshold and iteration settings are found on the Motion panel on the IK Controller Parameters Rollout, when the end effector is selected.
• The threshold and iteration settings for the HD solver are also found on the Inverse Kinematics tab of the Customize Preferences dialog.

Position Threshold

Sets how close the end effector has to get to the follow object or cursor position to be considered a valid solution. The value expresses a distance in the current unit system. Small values increase accuracy but take longer to solve.

Rotation Threshold

Sets how accurately the end effector has to match the orientation of the follow object to be considered a valid solution. The value expresses a rotation angle in degrees. Small values increase accuracy but take longer to solve.

Iterations

Sets the maximum number of times 3ds Max repeats the IK calculations to find a valid solution. A high Iterations value increases the chance that 3ds Max can calculate a valid solution, but takes longer to complete. The following rules apply:

• Calculations stop as soon as a valid solution is found, even if the maximum number of iterations have not been performed.
• The last solution calculated is used if the maximum number of iterations is reached, regardless of whether the solution satisfies the position and rotation thresholds.