From BlenderWiki

Editing Shape Keys

The edition of either relative or absolute shape keys is very similar.

Creating Shape Keys

You always create a shape key in Object mode, using either (in a 3D view) I (and then either the Mesh, Lattice, Curve or Surface entry, depending on the object’s type!), or, for meshes and lattices, the Add Shape Key button of the Shapes panel (Editing context, F9).

It is very important to understand this: when you edit an object with shape keys, you always edit its current active shape. When you add a new shape key, it is just a copy of the current active one. This implies that you must add a shape key first, and then edit it (using the Edit mode, ⇆ Tab).

The new shape key, unless it is the first one (called Basis), is named Key n (n being a number) by default. You can rename it (for meshes and lattice only…) by typing a new, more meaningful name in the relevant text field of the Shapes panel.

Each shape key creates an Ipo channel. However, they are also represented in the Ipo Curve Editor by horizontal lines (which are especially useful with absolute keys animation, as you will see later). The first (basis) shape key has an orange (yellow when selected) horizontal line. The other ones have blue (cyan when selected) lines. Do not confuse these lines with Ipo curves – they are just a materialization of the shape keys.

Note that:

• The first created shape key is special. As its name (Basis) states it, it serves as shape reference, especially with the relative keys.
• You cannot add shape keys from the Ipo Curve Editor (you will see why later).
• The shape keys can be created at any frame (relative ones are by themselves completely time-independent, and the “timing” of absolute keys can be adjusted in the Ipo window, see the next page).
• Consequently, shape keys are always added with I in the 3D View, even if they are located at the same position. Use this to copy shapes when inserting.
• You add relative or absolute shape keys exactly the same way – as said above, you can switch between both behaviors to your liking.

Selecting Shape Keys

Before editing a shape, you must select it. Note that for shape keys, there is no difference between “selected” and “active” – it is therefore not possible to select multiple keys at once.

You always select a shape key in Object mode, using:

• The Ipo Curve Editor window, by clicking RMB on its colored horizontal line, or selecting (LMB click) its corresponding Ipo channel.
• For meshes and lattices only, the Shapes panel (either cycling between your shapes with the left/right arrows, or directly with the drop-down list).

The object will take the shape corresponding to the selected key, until you change the current frame (which will make it return to the “Ipo playback” state). Note that as soon as your object has one shape key, there will always be one selected (its name is shown in the bottom left of the 3D views, next to the object’s name).

Editing Shape Keys

Shape keys edition can be split in two main parts: the shape edition itself, and the shape’s properties.

Editing Shape

As already stressed, you always edit the current selected shape key. So you must first select it (as detailed above).

Then, you just enter Edit mode (⇆ Tab), edit your vertices/control points to your liking, and return in Object mode to validate your changes.

This is crucial to understand: all shape keys of an object have the same topology. This means that:

• If you add a vertex/control point, an edge or a face in one shape, it will automatically appear in all other shapes (at exactly the same place, until you edit it).
• If you delete a vertex/control point, an edge or a face in one shape, it will also be deleted in all other shapes.

So, if you modify the topology of a shaped object, you’ll have to edit all its shapes again, especially if you add something.

There are also two editing tools (reserved to meshes, it seems…), available through the Specials menu (W), which might help you when editing shape keys:

Blend From Shape

This will blend the current selected elements with their state in another shape key.

Once the tool is activated, you must select (in a pop-up menu) from which key you want to blend, and then to what extent you want to blend, from 0% (no blending) to 100% (full blending), either by horizontally sliding your mouse cursor and then clicking LMB , or by directly clicking MMB to have a full (100%) blending.

For example, if you are editing key smile and want to recover the Basis state of the left part of the lips, you would select these vertices, hit W   »  Blend From Shape, then select the Basis key, and MMB to fully blend them to the Basis key.

Propagate To All Shapes

This will propagate to all other shapes the current state of the selected elements. Useful to “reset” all shape keys for only a portion of your object.

Editing Shape Properties

You edit the shape keys’ properties in their panel from the Editing context, F9 (Shapes for meshes and lattices, Curve and Surfaces for curves and surfaces).

The main shape key property (and the only one available for curves and surfaces) is obviously the toggle between relative and absolute keys (the Relative/Relative Keys button).

The Shapes panel.

Relative shape keys, basis key.

Relative shape keys, non-basis key.

Absolute shape keys.

However, for meshes and lattices shapes keys, you have additional features. The first row of controls is common to both types of keys:

The “pin” and “eye” buttons

These control the pinning/muting of the current shape key (see below).

The two arrows, and the drop-down list

As we saw above, these controls allow you to select a shape key.

The text field

This is where you can rename your keys.

The “X” button

It allows you to delete the current key (see below).

You then have options specific to the type of keys:

Absolute keys

Slurph

This is a time range (in frames) during which the movements of the vertices from one key to the next is spread (the order is the vertices’ one, i.e. first vertex moves first, last vertex moves last).

This gives a sort of “twisted sliding”, as the vertices do not use the same shape key at the same time…

For example, if you set Slurph to 10, the first vertex will move as if the shape Ipo curve (see later on) had been slid ten frames sooner, the “middle” vertex, as if the Ipo curve had been slid five frames sooner, and the last vertex follows the actual curve…

Relative key

This applies to all relative shape keys but the Basis (first) one!

The second row of controls

They are dedicated to Ipo animation, so we will see them in the next page.

VGroup and “base key” drop-down list

By default, a relative shape key is blended from the Basis (first) key. By selecting another key in the drop-down list to the right, you can blend it from this key.

Moreover, by default, all vertices of the object are affected by the key (i.e. if you want to only blend/deform one area of your object, you have to make sure that the rest of the two shapes – the one used as basis, and the deforming one – are the same). Well, there is a much easier way to do this: create a vertex group, and enter its name in the VGroup text field – vertices with a null weight will never be affected by the “deforming” key (they will remain as in the “basis” key), and the other ones will be affected proportionally to their weight in the group…

Note that this also allows you to have a static, vertex-level weighting of a shape key, multiplied with its animated influence (which is common to all vertices).

Deleting Shape Keys

You can delete an active shape key by:

• In the Ipo Curve Editor window, deleting the relevant Ipo channel (X).
• In the Shapes panel (meshes and lattices only), clicking on the “X” button to the right of the key’s name.

When you delete all shape keys, the object will remain in the last deleted key state!

Pinning

Location of the “pin” button in the Shapes panel.

Location of the “pin” button in the Ipo Curve Editor window.

When a mesh object does not have a pinned key, it can show multiple keys at once, and with various influence levels (as controlled by the Ipo Curve Editor, or any other animation tool).

To prevent this, click on the “pin” button (either in the Shapes panel, for meshes and lattices, or at the top of the left list of channels, in the Ipo window, for all types of object). The current object is now locked at that shape key, and will only show that key. This feature is useful when multiple keys are affecting an object and you would like to see the effect of a specific one.

An other use for pinning is to create a shape gallery (i.e. have simultaneously a representation of each shape key). Blender allows the creation of linked duplicates of an object (AltD), which share underlying data (e.g. mesh and shape key data). Once a duplicate has been created, move it to a different area of the screen and pin it to a shape key. Reselect the “original” object, and repeat the process for each shape key. You’ll get a shape gallery (which also helps in editing keys).

Pinning shape keys can also help to speed up interaction with a mesh (especially when animating it with armatures). If a shape is pinned, Blender doesn’t have to calculate the myriad of interactions and blends of different keys in real time, which speeds up operations. This is particularly useful when using armature-driven shape keys to correct deformations, since it’s usually not something critical that you need to see when animating. Remember to un-pin the shapes when you’re done and ready to render though!

Muting

You can also mute relative shape keys, to make them never affect your object (this is kind of complementary to the “pin” option…).

To mute a key, select it, and enable the “eye” button near the “pin” one, in the Shapes panel.

Note that:

• Absolute shape keys are not mutable (the “eye” button has no effect).
• Unfortunately, it seems you cannot mute curve/surface relative shape keys…