In this recipe, we'll set the shape keys to create (even if limited) facial expressions and to fake the stretching and the contracting effect of the character's arm muscles, and we'll add some more shape keys to fix issues in the character's shape.
First, let's prepare a bit the scene and the model:
Gidiosaurus_skinning_rigify.blend
file, which is the same as the Gidiosaurus_skinning_03.blend
file but with the rig created by the Rigify add-on (and later edited to add the other bones exactly as explained in the last chapter's recipes).Gidiosaurus_shapekeys.blend
.Let's start now by creating the facial expressions shape keys:
Note that we selected two faces instead of the folder edges, because the muscular scrunching involves both movement of the skin and a slight folding of the skin as well; the middle edge does not move as much as the selected faces due to PET falloff, hence creating a very slight scrunch and a more naturalistic skin sliding.
Each shape key now works only on the respective side, according to the selected vertex group:
This was for the grin expression; now we need to add at least two or three more kinds of shape keys, namely: two for the eyebrows (up and down) and one for the nostrils, multiplied for each side.
This means six more shape keys in total, but as you have seen, the procedure is quite quick and simple.
Note that, when naming the shape key for the enlargement of the nostrils, I erroneously wrote snare; it should have been something like snarl or flaring, but in the end it's just a naming convention and therefore, this little mistake doesn't pose a real problem.
We are done with the facial expressions; now let's add one more shape key to enhance some of the body features of the Gidiosaurus a bit; these are not meant to be animated during the animation, but are simply a way to apply non-destructive modifications to the model.
Now, let's add a couple of shape keys to mimic the movement of the main muscles of the arms, specifically of the biceps and of the triceps muscles:
More shape keys could be added to simulate a complete muscle system, but in our case we stop here with the Gidiosaurus mesh; now let's concentrate on the Armor.
Although technically there are no differences, we could say that we created three different types of shape key:
Shape keys work in linear space; that means that it's not possible to make vertices rotate around a pivot through a shape key, but only to move them from point A to point B. That's why we didn't use shape keys for stuff like the eyelid movements, for example, or the opening/closing of the jaw, but only for actions including muscles sliding above the bones such as the eyebrows, the grin, and the nostrils, as well as the bicep/triceps movements.
Thanks to shape keys, we also made last minute modifications and improvements to the Gidiosaurus mesh and to the Armor; being included inside a shape key, all these modifications are non-destructive and can be turned on or off at will, or their influence can be set at an intermediate strength value.
When modifying a mesh using a shape key, be careful not to change too much of the mutual proportions of articulated parts of a to-be-deformed mesh; for example, it's usually problematic to scale a whole part such as the hands or the head of a character, both smaller or bigger, unless you also scale the corresponding bones of the rig and the joints' position accordingly as well.
Beyond a certain threshold, the bones of the fingers, or of the eyes and jaw, start to be out of register compared to the respective mesh's edge-loops and you'll have to fix this by re-positioning the joints of the Armature's bones (just in case, remember: always do this in Edit Mode).
In our example, with the prop shape key, we just restricted ourselves to enhance the hands' knuckles and to make stronger feet by simply making the vertices' positions grow in the direction of their normals.
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