Getting Started with Shape Keys

In this chapter, we will cover shape keys, going from a basic introduction to getting hands-on with making and modifying our own shape keys. After covering shape keys, we will discover how bone drivers can be used to automate the input for these shape keys, activating them based on bone movement.

In this chapter, we will cover the following topics:

• Introducing shape keys
• Making a shape key
• Editing a shape key
• Using drivers
• Mirroring shape keys

By the end of this chapter, you will be able to add, remove, and modify shape keys to fix poor deformations and will know how to make shape keys an automatic part of a rig.

Introducing shape keys

Shape keys are an exceptionally powerful and infinitely versatile system that stores the local position of every vertex. Shape keys are essentially a stored shape that a mesh can take using the current set of vertices.

A shape key consists of two elements, a base and the shape we want to morph into. Shape keys are relative to the base shape, meaning that instead of holding a specific shape, they hold a delta (i.e., the difference) from the base to the target shape.

This idea of shape keys being deltas might sound strange at first, but it’s this very trait that gives them their power. It means we can start from a base shape, add a shape key, then add another one on top, or even subtract shape keys. This means any part of the mesh can be modified by multiple shape keys, with each shape key adding or subtracting its own shape to produce an almost procedural result.

How can we use them? In the form of corrective shape keys. Corrective shape keys allow...

Making a shape key

This section will start us off by getting to grips with adding shape keys, covering the menus that you will need to navigate to create these shape keys. Working on the basis and then creating the additional shape keys that we can edit later on:

1. Let’s look at how to make a shape key. The first one will automatically be named Basis, our base shape key. To add a new shape key, navigate to Object data properties | Shape keys and click the + button.

   This new shape key will automatically be named Basis. Do not delete or modify this in any way. Basis stores the base mesh without modifications and is what any subsequent shape keys spring from. This navigation process is shown in order in Figure 7.2:

Figure 7.2 – Navigating to the Shape Keys UI

2. Now that you have a base shape key, go ahead and click the + button again to add our first real shape key.
3. You should give each shape key a name that makes it easy to...

Editing a shape key

In this section, we’re going to take the shape key we made previously and modify it, as the shape key as it stands currently is not much use. This section will be making heavy use of Edit Mode and Proportional Editing.

In Edit Mode, we will modify this shape key manually to fix the poor deformation using the same controls covered in Chapter 2 to select vertices and move them into position.

There are a few things that we need to take care of before we start editing our shape key:

1. In Object Mode, go to the Armature deform modifier on the mesh and select Edit Mode: Display modifier in Edit mode.

   This means as you edit your shape key, you will be able to see the result when the mesh is following the bones. This removes the need to flick between modes in a trial-and-error fashion.

   The following screenshot shows how to show your work in Edit Mode:

Figure 7.3 – Showing Armature deform modifier in Edit Mode

...

Using drivers

Drivers within Blender allow you to drive any input field with external numbers from other objects in the scene. In our case, we want to drive that Value slider for the shape key with the rotation of the thigh so that as we pull the leg back, its rotation drives the value of the shape key, making the process of applying shape keys automatic for any animators. If this wasn’t the case animators would have to go through each shape key and manually add keyframes for their values.

This section will cover the creation of drivers, moving through each menu and popup to dig up this well-hidden Blender feature. Then we will move on to setting up the input of these drivers, choosing what bone we want to use to interact with this driver. By setting up the input, we will also set up the output – what we want this driver to do, which is drive a shape key!

We will finish with the complex task of adjusting this driver by using the Driver Editor, a neat tool that lets...

Mirroring shape keys

After all that work on the shape key, we don’t want to have to do the same on the other side manually as that would take up a lot of time and would be asymmetrical. Thankfully, Blender lets us mirror shape keys. The following steps show how to mirror a shape key:

1. Select the shape key you wish to mirror and ensure its value is currently 1, either by moving the slider or by posing any bones that drive the shape key. Make sure any other shape keys are 0 (you can simply delete drivers by right-clicking the Value slider).
2. Click the dropdown in Figure 7.9 (marked 2) to bring up the options for the currently selected shape key.
3. Use New Shape from Mix to create a new shape key that is a mix of the currently active shape keys. You can make a mix from an infinite amount of shape keys, but for now, we will use Basis and the shape key you wish to mirror.
4. Select this new shape key, go to the dropdown again, and use the Mirror Shape key. Note that...

Summary

In this chapter, we have covered the use of both shape keys and drivers to modify geometry automatically with bone input. Understanding how drivers work and the importance of taking steps in the correct order will minimize time lost through error. We started the chapter by covering the creation of shape keys, remembering that you can use Sculpt Mode to make shape keys much faster (so you should go learn some sculpting!). We then moved on to the creation of drivers and the Driver Editor that can be used to modify these drivers. We finished the chapter by mirroring the shape keys to reduce our workload and ensure symmetry.

Before moving on to the next chapter, use the examples in Figure 7.10 and Figure 7.11 to practice and make more shape keys and drivers to improve areas of poor deformation. You will undoubtedly find more areas that could use the magic of shape keys, so don’t be afraid to experiment!

In the final chapter, we will cover more advanced rigging ideas...