To create shape animation by selecting shape keys (sometimes called blend shapes), you first create a series of similar objects deformed in different ways. The objects must have the same type of geometry (polygon mesh or NURBS surface) and the same topology (number and arrangement of points) as the target object that they’re shape-animating. The easiest way to do this is to duplicate the target object that you want to shape-animate, and then deform each of the copies in a different way that will correspond to a shape key.
You then select the target object or cluster on the target object and pick (select) the deformed objects in a specific order to create shape keys. If you select a cluster, only the portion of the object that corresponds to this cluster creates the shape key—the rest of the object is ignored.
Selecting shape keys sets up a relation between the target object or cluster and the shape keys, allowing to you fine-tune the shape keys and have those adjustments appear on the target object or cluster. For example, if your client thinks that the nose is too long on one of the shapes, all you have to do is change the nose for that shape and it updates the nose on the target object. However, you can choose to not keep this relationship between the target object/cluster and the shape keys (see Breaking the Link between the Target and Its Shape Keys).
When you’re done selecting the shape keys, you can have them automatically instantiated in the animation mixer to create shape clips, or add them to the mixer later. See Applying Selected Shape Keys Automatically for more information.
If you don’t want to use the mixer, you can apply each shape key to the base object at different frames (see Applying Shape Keys).
Selecting Shape Keys for the Target
To select shape keys
1. Create the target object that you want to shape-animate.
2. Duplicate this object as many times as the number of the shape keys you want to set. Move them out of the way of the camera.
3. Deform the duplicates using any method of deformation (you can even animate the deformations). In this example, the mouth is deformed into different shapes on each of the duplicated heads.
4. Select Shape Modeling from the Construction Mode list on the main menu at the top of the interface.
5. If you want to create shape clips automatically in the mixer when you’re finished selecting the shape keys, choose Deform > Shape > Preferences, then select the Apply Selected Shape Keys option in the Shape Preferences property editor.
6. Select the target object or cluster that you want to shape-animate. If you select a cluster, only the portions of the object corresponding to the selected cluster are used to create the shape keys.
7. Choose Deform > Shape > Select Shape Key from the Animate toolbar and pick each of the deformed objects in order.
- Click to pick objects and middle-click to pick branch objects.
- Right-click when you have finished to end the picking mode.
8. In the dialog box that opens, label the first shape created in the Name text box. The other shapes use this name plus a number, such as face, face1, face2, etc.
For each shape you pick, a shape key is added to the model’s Mixer > Sources > Shape folder.
Play back the animation to see the target shape change using the different shape keys you set.
9. Do one of the following to apply, sequence, and/or mix the shapes:
- Apply the shape keys to the target object at different frames—see Applying Shape Keys.
or
- Load the shape keys as clips into the mixer where you can sequence and mix them—see Using the Animation Mixer for Shape Animation. If you chose the Apply Selected Shape Keys option before you picked the shape keys, the shape clips are already in the mixer.
If you drag the shape keys to the mixer tracks, the resulting shape clips are 10 frames long. You can then resize and layer the clips, add transitions between the clips for a smooth change between shapes, and change the weight of each shape clip against each other.
As well, you can put create a compound clip that contains all these clips so that you can mix and copy them easily.
Applying Selected Shape Keys Automatically
With selected shape keys, the mixer is a powerful tool that lets you easily sequence, rearrange, and mix the weights of the shape keys as you like. If you know you want to use the mixer, make sure to activate the Apply Selected Shape Keys option before you choose Shape > Select Shape Key and pick the deformed objects for shape keys.
When you’re finished the picking session, this command applies the shape keys to the target object or cluster and automatically creates a shape clip for each shape key in the mixer. The shapes are instanced in the mixer using the currently selected instancing mode, with Mixed Weight being the default (see Choosing a Shape Instance Mode for Shape Clips).
To automatically apply selected shape keys
1. Choose Deform > Shape > Preferences from the Animate toolbar or File > Preferences from the main menu.
2. In the explorer that appears, select Shape Animation or click its icon.
3. Select the Apply Selected Shape Keys option.
Breaking the Link between the Target and Its Shape Keys
Selecting shape keys sets up a relation between the target object or cluster you’re shape-animating and the shape keys it’s drawing from. This is done via a Copy Shape operator in the shape’s cluster that continually copies from the shape-key objects. Because of this operator, you can adjust the shape keys and have those adjustments appear on the target object or cluster that they’re deforming.
However, you can choose to not maintain this link after you’ve finished selecting the shape keys, or manually break the link at any time. Once you have done this, changes to the shape keys no longer affect the target object or cluster.
To create shape keys without maintaining the link
• Choose Deform > Shape > Preferences and deselect the Relational Select Shape Keys option in the Shape Preferences property editor before you start selecting the shape keys.
By default, this command is active, which means that the deformed objects that you pick for the shape keys continue to drive the shape animation. When this command is off, the link between the shape-key objects and the target object or cluster is broken after you’ve picked the shapes.
To break the link between shape keys and the target geometry
1. In the explorer, expand the object with shape animation, then expand its geometry node, its Clusters folder, and the cluster associated with the shape animation.
2. Expand the cluster key associated with one of the deformed objects you selected as a shape key. By default, the cluster key name begins with the same name as the target object and ends with _ShapeKey.
3. Freeze the Copy Shape operator under the cluster key by selecting it and clicking the Freeze button in the Edit panel.
4. Repeat this procedure for each of the shape keys whose link you want to break.
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