Animation > IK > Run IK

Run IK Options

Skeletons

All – If you select All, the Run IK simulation runs on all root-level skeletons that have multi-chain IK handles, whether or not they are picked.

A root-level skeleton is a joint node with no ancestors that are joint nodes. This joint node and all joint nodes below it make up a skeleton.

Active – If you select Active, the Run IK simulation runs on all joint nodes on the skeletons that are active.

The skeletons are defined from the picked joint node and all joint nodes below it. Anything that is picked but is not a joint node will be ignored.

Frame Range

Note

Multi-chain IK animation must be run from the same initial state to get the same animation.

Note

For Run IK with multi-chain handles, the skeleton must be in a known starting position.

Note

If you want to render only a subset of the frames in your animation, you must still follow the above steps and run IK for the whole range of animation.

All – The default frame range includes the range of animation for all the IK handles attached to the picked skeletons.

Current – The IK simulation starts at the current frame and runs until you press the key.

Option Window – Lets you specify start and end frames. When you click this button, these controls appear:

You can specify the frame range for the IK simulation by typing the Start Frame and End Frame values. These values apply for running the IK simulation only if Option Window is selected.

By Frames

This is how often keyframes are set for a skeleton during the IK simulation. If the Simplify option is ON, some of these keyframes may be removed after the simulation is complete.

Sample Rate

This is the increment at which the Run IK simulation is run. For example, if the Sample value is 0.2 frames and the By value is 1.0, then the IK simulation runs for 5 steps for each frame before setting a keyframe in the skeleton.

Since the IK handle animation is sampled at different frame values, inverse kinematics may cause a jump from one frame to another. Choosing a smaller Sample value makes the inverse kinematics solution smoother, even though keyframes are generated only at the By Frames increments.

Simplify

If the Simplify option is toggled ON (indicated by a check-mark), all the animation curves that were created in the skeleton during the IK simulation are simplified after the simulation to remove as many keyframes as possible within the given tolerance, while still preserving the shape of the original curve.

When it is checked, the following additional controls appear:

Translation/Rotation Tol – These tolerance values are used for simplifying the curve. A tolerance specifies how much the simplified curve may differ from the unsimplified curve at each keyframe.

These two sliders let you specify different tolerances for curves that are animating joint rotation versus those animating joint translation. For example, the default tolerance for rotation is higher than that of translation because a difference of one degree of rotation is usually less noticeable than a difference of one unit of translation.

Disable multi IK

If this option is set ON, all multi-chain IK handles are disabled after the Run IK simulation.

Redraw

If this option is set ON, each time a keyframe is computed, the skeletons are redrawn in their configuration at that frame. This gives instant feedback for the Run IK simulation.

Tip

If a large model is simulated for many frames, redrawing at every By value can slow down the simulation. If you toggle Redraw off, the skeletons are redrawn only at the beginning and end of the simulation.

With Single/Spline IK

If this option is set on, any single-chain IK and spline IK animation information is also translated into rotational information on the skeleton in addition to the translated multi-chain IK. When you select this option, the following additional controls are displayed:

Disable Single/Spline IK

This option turns off the single-chain and spline IK handles after Run IK is applied. To turn the single-chain and spline IK handles back on, use Edit > Rest Pose > Set Rest Pose, or the Information Window.

Compensation

If you are going to render an animation with Motion Blur, or Fields Render (see Render > Globals for details), you may want to use motion blur compensation, field render compensation, or both during the Run IK simulation. These compensations only apply on animations translated from single-chain or spline IK handles.

Motion Blur – Run IK simulation sets extra keyframes at motion blur sample times if interpolation between keyframes would yield wrong values for motion blur. The Shutter Angle used for the motion blur compensation is set in Render > Globals > Blur Effects.

Fields Render – Run IK simulation sets extra keyframes at half frames if interpolation between keyframes would yield wrong values for half frames. Field rendering information is set in Render > Globals > Image File Output.

None – Compensation does not occur (this is the default).

Both – Both motion blur and field rendering occur. By default, Compensation is set to None. Otherwise, the following additional controls appear:

Detection Only

If set to ON, animation is not translated to the skeleton. Instead, the compensation information appears at the prompt line; you are told if compensation is needed and at which keyframes it should be applied.

Translation Tol/Rotation Tol for Compensation

These tolerance values are used to determine if a compensation between two keyframes is needed or not. Each time the compensation procedure checks an animation, if the real translation value is within the tolerance, no compensation happens. Otherwise a new keyframe is inserted with the real value.