Join Jason Baskin for an in-depth discussion in this video Understanding morph targets, part of Rigging a Face in Maya.
We're going to begin exploring one of the more basic techniques for creating a facial rig, the blend shape approach. But while this approach is relatively easy to set up, it can still result in a very robust and expressive rig, if the morph targets are created with maximum compatibility in mind. Creating a blend shape is actually really simple, you just select a target or a series of targets. And then Shift Select the neutral position for the character and under the animation module, go to Create Deformers, Blend Shape.
This is going to create a new input for the character, and if we expand it from the channel box, and select the name of the target, we can middle mouse drag to activate this blend shape. These targets can also be activated from the Window, Animation Editor, Blend Shape Window, which creates a slider for you. So this character was modeled to have a facial expression where he maybe looks a little scared or disgusted. And it's triggering lots of different portions of the characters face, the lower lids are being raised the nose is flaring and the corners of the mouth are pushed down.
And, while this makes a lot of sense from a modeling standpoint it's actually sort of limiting from a rigging standpoint. Because an animator may want to activate the lower eye lids totally separately or have the character's nose flare only when he's having another facial expression. So it's much better to try to isolate these different blend shapes into their component parts. One of the ways that this can be done is actually to paint the areas of influence of this blend shape into this character. So if I activate the blend shape target and select this mesh, I can go to Edit Deformers, Paint Blend Shape Weights, Options, which will bring up the artisan painting tools.
These allow us to determine which areas are going to be effected by the active blend shape. I'll select the target. And by setting my value to zero, with the operation set to replace. I can actually paint out areas of influence for this target. For example, completely eliminating the lower eye lid. I could also feather this back in with the smooth operation. Or add values back in by setting my value above zero or closer to one to paint in areas of influence. So when a full character emotion has been created this way.
It's actually really easy to break it into component pieces. And breaking the facial expression into these different components, will give us much more flexibility with the rig. So I'm actually going to delete this blend shape by typing delete, and then the name of the input which is blend shape one down here in the command line and hit Enter. This will remove the blend shape entirely, and this time I'm going to add four separate blend shapes. Which were constructed to address specific areas of the character's face.
This blend shape triggers the mouth, this one triggers the nose flare, this one triggers the right lower eyelid, and this one triggers the left lower eye lid. I'll select these targets one at a time. Shift Select the neutral position for the character, and choose Create Deformers Blend Shape. If I bring back my blend shape window from the animation editor, I can activate these blend shapes individually and also combine them to create the same facial expression that I initially started with. If a character has already been bound to a skeleton mesh, a common problem is that the blend shape will seem to slip off of the skeleton when its activated.
Default setting will often append the blend shape node after the skin cluster, and this is the incorrect order. So to fix this, you'll want to select the mesh, right click, and chose Inputs, All Inputs. And then you'll have access to the input operations for this mesh. I'll select the blend shape node, and middle mouse drag it beneath the skin cluster, so that the blend shape is triggered before the skeletal deformation. This will ensure that the character's facial expression changes before the skeleton moves the head and the neck around. To avoid having to do this operation entirely, a better option would be to go to Create Deformers, Blend Shape Options, and under the advance tab, select Front of Chain for the deformation order.
This will order the blend shape properly when it's appended to a character that already has a skeletal rig. As you can see, blend shapes offer artists a quick and easy way to control deformations which would be very difficult to achieve with joints and other deformer types. And with a bit of planning your blend shape library can be mixed and matched to create an incredibly versatile range of facial expressions.
- Understanding morph targets
- Using Soft Select, Artisan Sculpt tools, and symmetry options
- Splitting symmetrical shapes into asymmetrical pairs
- Connecting eye rotation to the GUI
- Working with eyelids, using blend shapes or fan joints
- Creating a basic UI control
- Connecting controls
- Orienting joints and creating a support structure
- Attaching joints to the support structure
- Binding joints to the final mesh
- Balancing shape fidelity with rig density and usability