Modeling Shape Keys
The first step in creating the facial rig is to model the necessary shape keys. You need to isolate different parts of the face and create different shape keys for each part. Here are a few examples of the shape keys you can create: smile, frown, blink, open mouth, and move eyebrows up and down.
For each one of those actions (except the ones that affect both sides of the face simultaneously) you will have to create two shape keys, one for each side of the face. For example, you’ll want the left and right eyelids to blink simultaneously. For Jim, things will be pretty simple because you don’t need dramatic facial expressions; he just needs some basic things like smiling and blinking, so you can keep the shape keys to a minimum. However, if you want to create a very realistic facial rig, you might need a lot of shape keys. In Figure 11.12, you can see the Shape Keys panel, on the Mesh tab of the Properties Editor.
Figure 11.12 The Shape Keys panel on the Mesh tab of the Properties Editor, where you can add, remove, and adjust shape keys on the list
Creating Shape Keys
Here is how shape keys work: You start with the key called Basis, which is the base shape key on which all the rest of the keys are built, as this is the model itself. After that one, you can click the + button in the upper-right side of the panel to add a new shape key to the list. Double click it to name it. Let’s say you’re going to create the smile shape key, so you’d name it something similar to mouth_smile.L (this is the left side of the mouth that will be smiling). Now, with that shape key selected, if you enter Edit Mode, you can manually reposition the vertices to create a smiling shape on the left side of the mouth (Proportional Editing tools are really useful in this stage).
When you exit from Edit Mode, you’ll see that the model jumps back to its original shape key and you don’t see the smile. This happens because the smile shape key moves back to the 0% effect. Near the shape key’s name, there is the Value slider (see Figure 11.12) that you can drag left and right to increase or decrease the shape key’s value. Also, you can select the shape key and drag the Value slider under the list.
At the bottom of the panel, you can control the range of the current shape key’s values (usually from 0 to 1). If you set the value to a maximum of 2, for example, the shape key will be able to continue the movement of the vertices until they reach double the effect that you modeled originally.
The idea is that for each part of the face, you have different shape keys that you can mix together to create facial expressions. Happiness, for example, would be a smile, maybe the lips a little opened, the eyes partially closed, with the cheeks and eyebrows lifted. So the mix of those different shape keys would help you create the expression of happiness on the face. In Figure 11.13, you can see examples of mixing some very basic shape keys to create different expressions on Jim’s face.
Figure 11.13 Jim’s shape keys in action, with parts of the face moving together to create full face expressions
Mirroring Shape Keys
As you saw before, you need to isolate some shape keys on one side of the face. For example, you need a right eye blink and a left eye blink. However, if your character’s face is symmetrical, modeling the shape keys manually for both sides will be tedious and it may result in the shape keys producing different effects for each side. The following instructions show you how to mirror shape keys:
1. Create one side’s shape key, such as the blink for the left eye.
2. Exit Edit Mode and set the value of the left eye-blink shape key to 100%.
3. Click the down-pointing triangle button just below the + and – buttons to add and remove shape keys from the list. Select the option New Shape rom Mix: this will create a new shape key with the vertex positions that include the values of shape keys currently in use. Rename the new key for the right side.
4. Click again in the same button and select the option Mirror Shape Key. This will translate the vertex positions to the other side of the mesh.