Controlling IK Precision (HD Solver)

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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 Autodesk VIZ repeats the IK calculations to find a valid solution. A high Iterations value increases the chance that the software 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.

Setting Applied and Interactive Thresholds

You set the threshold and iterations settings as a trade-off between accuracy and speed. You have two groups of settings so you can individually tune the behavior of applied IK and interactive IK.

Use interactive IK if you want fast, real-time response. Your interactive IK preferences should be set for speed.
Use applied IK if you want the solution to match the follow objects very closely. Your Applied IK preferences should be set for accuracy.

The default applied IK and interactive IK settings are shown in the following table:

Thresholds	Applied IK	Interactive IK
Position	0.100	1.000
Rotation	0.100	1.000
Iterations	50	10

Controlling IK Precision (HD Solver)

Setting Applied and Interactive Thresholds

See also