Use animation layers to enhance motion capture data

Animation layers are especially useful for working with motion capture data. You can edit only those specific points in the animation that require changes and leave the rest of the data untouched.

Animation layers can help you clean up many common issues with motion capture data, including body interpenetrations, shakiness in the feet or hands, and unstable floor contact. You can also use animation layers to make sure objects hit specific targets in the scene.

The following steps describe a sample workflow using animation layers over motion capture data to stabilize a character’s wrist as it comes in contact with the ground.

To use animation layers to correct or enhance motion capture data

1. Load a sequence of motion capture data into your scene.

   This example describes a scene with motion capture data plotted to a biped skeleton.

   In this example animation, the wrist makes contact with the floor at frame 27, but the position of the hand is shaky and unnatural. We want the hand to hit the floor at frame 27, then stay steadily planted between frame 27 and 40. You can modify the animation between those frames to stabilize the hand as it makes contact with the floor.

   
2. Insert a single chain solver between the shoulder and wrist by doing the following:
   • Select Skeleton > IK Handle Tool > from the main menu bar.
   • Select the shoulder as the start joint, then select the wrist as the end joint. (See also Create IK handles.)
   • In the IK Handle Settings, select ikSCsolver as the Current solver.
   Note

   This example uses a single chain IK solver, but you can also use the effector on a HumanIK rig to achieve the same results.

   In the next steps, you’ll use the IK handle as an effector to manipulate the position of the wrist.

3. Select the IK handle you just created, then select Layers > Create Override Layer From Selected in the Animation Layer Editor menu bar. (See also Create an animation layer.)

   A new Override layer called AnimLayer1 is created for the IK handle in the Animation Layer Editor stack.

   By default, all of the handle’s attributes are added to the layer, including its IK Blend value. (See Add and remove attributes from animation layers.)

4. Double-click the new layer and rename it “Stabilize_Hand”, then click to mute the layer.

   Muting the layer lets you view the original animation and identify the frames you want to modify. Even though this layer doesn’t yet contain animation, it is in Override mode which can cause the IK handle to display in an invalid position unless the layer is muted.

   By default, layers are also locked from receiving keys when they are muted. You can change this option by turning off Options > Lock Muted Layers in the Animation Layer Editor. In the following steps, we will unlock this new layer so it can receive keys.

5. Play the animation to determine where you want to stabilize the hand/wrist.
   
6. Click to unlock the layer for keying.
7. With the IK handle selected, set a key at frame 27.

   This fixes the position of the IK handle at frame 27. (See also Keyframe objects on animation layers.)

   In the Animation Layer Editor, notice the green “traffic light” feedback on the Stabilize_Hand layer. This indicates the layer is active for keying.

   Because you created the layer for the IK handle in step 3, the keys you set on the handle are contained on that layer. Since the layer is in Override mode, its animation will override the motion capture data when you unmute the layer and play the animation in your scene.

8. Click to unmute the layer and play the result animation in the scene.

   In the next steps, you will keyframe the handle’s IK blend value so that its effect (modifying the original animation) blends in over several frames.

9. Key the handle’s IK Blend value as follows:
   • Go to frame 0 (before you want to modify the hand/wrist animation), set the IK blend value to 0, and set a key.
   • Go to frame 20 (where you want the modified animation to start blending over the original data), set IK Blend to 0, and set a key.
   • Go to frame 27 (where you want the modified animation to completely override the original animation), set IK Blend to 1, and set a key.
10. In the Graph Editor, adjust the IK Blend keys you have just set to use linear tangents. (See Edit tangents and Linear.)

    After frame 27, the hand is now stabilized as it comes in contact with the floor.

11. (Optional) If you are satisfied with the modifications, you can merge or bake your modified animation with the motion capture data. See Merge animation layers and Bake animation layers.