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Shape Keys

Mode: Object mode

Panel: Shapes (Editing context, F9)

Shape keys store different shapes of a same object (mesh, curve, surface or lattice). In other 3D applications they are called “morph targets”, “blend shapes”, or even “vertex keys” in older versions of Blender. They are the only way to directly animate the shape of your object.

Shape keys are the specified positions of vertices or control points within an object. Since this can involve thousands of vertices for an object (especially a mesh), separate motion curves are not created for each vertex because it would overload your computer’s memory – and your own capabilities! A more generic keyed position system is used instead: a single (or a few) Ipo curve(s) is(are) used to determine how interpolation is performed and the times at which a shape key can be seen.

You can use them to directly animate a face, the folding of a sheet of paper, etc. But you can also use them as indirect animation tool – think for example in animating the shape of a curve used as bevel or taper for another one: this would allow you to animate a pumping artery, or a pulsing heart, or a growing worm, or balloon being inflated, or a tree growing… A scene in Elephant’s Dream, where worms started growing (just before Proog conks Emo) used animated bevels and tapers while the curves extended. Similarly, you can animate a lattice or mesh used (through modifiers) as a deforming cage for another object, or for particles…

And you have much much more possibilities!

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Other Usages…
Shape keys can also be used for completely non-animated purposes. For example, you might create shape keys of your mesh to store some given states of work in its modeling (just remember that all shape keys have the same topology).


Description

An example of mixed relative shape keys.
The Shapes panel of meshes and lattices.
The Curve and Surface panel of… curves and surfaces.

A shape key stores the positions (in the local space, of course) of an object’s vertices/control points, which determine its “shape”. Blender features two types of shape keys, differing mainly by the way they are animated:

  • Relative shape keys have (by default) one key (the first one) as basis, and all others can be used to blend this basis with their own shapes (optionally limiting their effects to a given vertex group). Each of these “relative” shapes’ influence can be animated with its own Ipo curve, exactly as you would animate the influence of constraints. You will use them, for example, to create and animate a face’s expressions and movements.
An object has relative keys if the Relative button of its Shapes panel (for meshes and lattices), or the Relative Keys button of its Curve and Surface panel (for curves and surfaces!) is enabled.
  • Absolute shape keys are all “equal”. They always apply to the entire mesh and are used to “morph” the object from one shape to the next (i.e. you can only have at most two shapes affecting your object at the same time). Hence you only have one Ipo curve to control the animation (i.e. to control where in the shapes’ succession must be the object) – and you can even use no Ipo curve at all, getting a default morphing… You will use them, for example, to animate an origami creation, a flower growing…
An object has absolute keys if the Relative button of its Shapes panel (for meshes and lattices), or the Relative Keys button of its Curve and Surface panel (for curves and surfaces!) is disabled.

Whatever type of shape keys you use, their settings and animation properties are gathered in two main areas:

  • The Shapes panel (for meshes and lattices) or Curve and Surface panel (for curves and surfaces!) of the Editing context (F9).
  • The Ipo Curve Editor with the Shape Ipo type.
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Note that:
  • A shape key (relative or absolute) simply defines a “final position” for a group of vertices: it does not say how fast the shapes are transitioned or in what order. You can make these keys in any order or speed you wish, and control the degree of influence (to make a “slight” smile, for example), using the familiar mechanism of Ipo curves.
  • Nearly everything possible with absolute shape keys can also be done with relative ones (the only exception seems to be the Slurph option…). So absolute shape keys might appear like a sort of “sub-set” of relative ones, using a different animation technique (see below).
  • You can’t have both absolute and relative shape keys on a same object – you have to choose one type!
  • You can safely switch between absolute and relative shape keys (neither their respective settings nor their respective Ipo curves will mess with each other).
  • With relative shape keys, you can have morph families. A morph family is a group of shapes related to an area of the object’s data. For example, take the face. You have the eyebrow area (possible shapes are “surprise”, “furrow”, “eyebrow lift-left”, and “eyebrow lift-right”), the eyelids (“blink”), the mouth (“smile”, “frown”), nose (“flare”, “wiggle”) and tongue (“ay”, “th”, “i”, “stickout”, “tunnel”). The “jaw open” action may be controlled by a bone. In this case you would add a vertex group for the eyebrow, another for the tongue, etc.
  • Shape keys are part of the ObData datablock (i.e. mesh, curve, etc.), not of the Object one. Thus, it is possible to permit multiple objects to share the same shape keys by simply making them use the same mesh (or curve, surface, etc.) datablock. This applies to both the shape keys themselves, and to their Ipo animation (i.e. Shape Ipo curves).
  • Unlike relative ones, absolute shape keys are always animated (see this page), even without any Ipo curve.

Workflow

The overall process for using shape keys in Blender is:

  1. Define your basis (or “rest”) shape.
  2. Identify the list of primitive morphs that you might want (for relative shapes keys) or the sequence of key shapes you need (for absolute shape keys).
  3. Optionally, create vertex groups for sets of vertices to participate in each morph family (relative shape keys only).
  4. Add your shapes (Object mode), and edit them (Edit mode).
  5. Using the Ipo curve(s), define when you want the target shape to influence the basis shape (for relative shape keys), or how the shapes succeed one to the next (for absolute shape keys).

When working on shape keys, you’ll likely want to have at least a 3D View, an Ipo Curve Editor and a Buttons window in your work space (use e.g. the Animation screen layout).

In the three next pages, we’re going to: