In-between shapes are target shapes that you add at weights that are between (but not including) the values of 0 and 1 for an existing target shape. They allow you to have finer control over certain deformations, especially useful for facial animation.
The in-between target shape can stay in an absolute state, or it can be relative to the state of the hero target shape (the target shape from which you are creating the in-between shape). If it's relative, when you edit the hero target shape (such as with sculpting), the in-between follows along in relation to the new shape. You can also select the type of interpolation to use for easing the in-between shape in and out of the hero target shape.
To create an in-between target shape
In the Shape Editor, drag in the target shape's weight slider to a value you want for the in-between shape. It can be at any value except for 1.
Choose Add Blend Shape In-Between Target Options.
> to select whether the in-between target shape will be absolute or relative to the hero shape, or set a Custom maximum influence weighting value, in theYou can also right-click in the hero target shape's weight slider and choose Add In-Between Target to create an absolute in-between target shape at the current weight value. Absolute is the default, but you can change this to Relative in the Add Blend Shape In-Between Target Options.
An in-between target shape is added beneath the hero target shape with its name and the maximum influence weighting value as a suffix.
An orange bar is added in the hero target shape's weight slider to represent the new in-between target's maximum influence weighting.
Select the in-between target shape and click the Edit button to begin editing the base object. The weight value on the hero target shape is automatically set to the in-between's orange bar in its weight slider (the in-between's maximum influence weighting).
You can repeat this process to add more in-between shapes for the hero target shape. Multiple in-betweens are ordered by their maximum influence weighting, from lowest to highest.
In addition to creating an in-between target shape "on the fly", you can add selected objects to create in-between target shapes, the same way you use multiple target objects to create target shapes. This can be the base object or another object.
If you select multiple objects for adding in-between shapes, the order in which you select the objects influences the subsequent weighting of those shapes. The in-between shape for the object you select first will use the current or custom target weighting that you have set, while every subsequent in-between target will increment that original weighting by double, triple, quadruple, etc., depending on how many objects you select. For example, if you select four objects, the first in-between target shape will be 0.2, the second will be 0.4, the third will be 0.6, and the fourth will be 0.8
To add objects as in-between target shapes
Choose Add Blend Shape In-Between Target Options.
> to select whether the in-between target shape will be absolute or relative to the hero shape, or set a Custom maximum influence weighting value, in theYou can also right-click in the hero target shape's slider and choose Add Selection as In-Between Target to create an absolute in-between target shape at the current weight value of the hero target shape. Absolute is the default, but you can change this to Relative in the Add Blend Shape In-Between Target Options.
Select the in-between shape and click the Edit button to begin editing the target object. The weight value on the parent target shape is automatically set to the in-between's orange bar in its weight slider (the in-between's maximum influence weighting).