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Handle channel node

The “engine” which drives Inverse Kinematic solutions using the Handle object.

The Handle chop is the “engine” which drives Inverse Kinematic solutions using the Handle object. The role of the Handle chop is to generate rotation values for the bones which will bring their attached handles as close to their respective targets as possible.

The use of this methodology is best described with an example:

  1. Increase the frame range to 10000. Create a Null object called 'target' and animate a few random positions for it to travel to.

  2. Create a three bone IK chain with No Kinematics. Append a Handle object to the last bone.

  3. In the Handle object set the Target menu to Target. This is the null object you just created.

  4. The system is now specified. To actually start the IK enter a CHOP pane.

  5. Place a Handle chop. In the Source field type in the names of the bones that were earlier created.

Tip: In the Viewport, you can use the Select state to select the bones you created. Then in the Handle chop click the Grab Source Form Selection button. The names are entered automatically for you. You don’t have to worry about being too picky when selecting objects this way, since non-bone objects are ignored.

  • Click the Export button on the Handle chop and click Play. You should now see the two-bone system chasing the animated null.

You can place any number of bones with any number of (possibly zero) Handles attached to the system. The following parameter description will now give a more detailed explanation of the functionality:

Parameters

Handle

Source

Creates rx ry rz channels for every bone listed.

Grab Source From Selection

Select bones in the viewport and select this to automatically enter bone names above. Non-bones are ignored.

Fixed

Enter groups of bones which are to rotate as a combined unit. (Eg, a shoulder or pelvic branch).

Grab Fixed From Selection

Select bones in the viewport and select this to automatically enter fixed bone names above.

Iterations

Specifies the accuracy of the solver.

Init Frame

Specifies a frame in which the bones are reset to their default rest angles.

Preroll

Specifies the number of iterations to solve at the initialization frame.

Max Angle Change

Specifies the maximum change in degrees the solver is allowed to move each bone per frame. Use this parameter if the solution is too drastic.

Channel

Single Frame

When ON, only the current frame is solved. When OFF a range of frames is solved. Turn this option off to cache and or edit the entire solution.

Unit Values

Specifies how the Start/End fields are evaluated below.

Start/End

Specifies a range of frames to solve for when Single Frame option is turned Off.

Sample Rate

The sample rate of the channels.

Extend Left

The left extend conditions.

Extend Right

The right extend conditions.

Default Value

The default value for extend conditions.