Adding Hooks

Shape keys work well for getting specific predefined deformations, but they can be pretty limiting if you want to have a little bit looser control over your mesh or if you're animating things that move in arcs. For these sorts of situations, you have another control mechanism: hooks. Hooks are a special kind of modifier that takes a set of vertices or control points and binds them to be controlled by another object, usually an Empty.

Creating new hooks

The workflow for adding a hook is pretty straightforward. You tab into Edit mode and select at least one vertex or control point. Then you press Ctrl+HHook to New Object. An Empty is created at a location that's the median point of all your selected vertices or control points. You also get a new modifier added to in Modifiers Properties, as shown in Figure 11-5.

Figure 11-5: Control options for the Hook modifier.

Tab back into Object mode and transform the hook. All the vertices or control points that you assigned to the hook move with it. And using the options in the Hook modifier, you can control how much influence the hook has over these vertices or control points. The following example gives you a clearer understanding of adding and modifying the influence of hooks:

1. Start with the default scene in Blender (Ctrl+N).
2. Select the cube and tab into Edit mode.

   All the cube's vertices are selected by default. If not, press A until the vertices are selected.

3. Do a multisubdivide with four cuts (WSubdivide, F6Number of Cuts: 4).
4. Select one of the cube's corner vertices (right-click).
5. Press Ctrl+Numpad Plus (+) a few times to increase the vertex selection.
6. Add a new hook (Ctrl+HHook to New Empty).
7. Tab back into Object mode.

   At this point, behavior is as expected. If you select and move the Empty, all the vertices that hooked to it move as if they're parented to it.

8. Increase the Falloff value in the Hook modifier to 1.00 (Modifiers PropertiesHook-EmptyFalloff: 1.00).

   Now when you select and transform the Empty, the way the vertices follow it is much smoother, kind of like when you're modeling with the Proportional Edit Tool (O). For additional kicks, do the next step.

9. Add a Subdivision Surface modifier to the cube and have it drawn smooth (Ctrl+1, Tool ShelfShadingSmooth).

   Now the transition is even smoother, as shown in Figure 11-6.

Figure 11-6: A cube smoothly deformed by a hook.

Knowing where hooks are helpful

The best use for hooks is for large organic deformations. Like shape keys, hooks are nice for creating muscle bulges and cartoony stretching. You can even use them along with shape keys. Because shape keys always use the same shape as the basis for deformation, adding a hook can bring a bit more variety. For example, in the bug-eyed Suzanne example from the “Creating Shape Keys” section, you can add a hook for one of the eyes to make it bulge asymmetrically. These touches give more character to your 3D characters.