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Modelers also often consider Maya's skeleton and smooth bind tools to be of little importance to their work. But in reality, these tools can be extremely effective for handling the creation of certain challenging morph targets. For example, one especially difficult target is the open mouth pose, which usually involves the translation and rotation of a large number of vertices from a specific point. But, with a very controlled falloff. Eyelids can create similar challenges, especially for characters with very large cartoony eyes.
But, attaching a simplified skeleton to these morph targets is a quick and simple process, and can give the modeler and technical director tremendous control over the creation of the shapes. So, here I have a duplicate of my base mesh, and I've named this one Jaw Open, and I want to use it as a morph target for my character. Now, I could certainly just create a jaw joint for this character. You can see that the character already has a full body skeleton. And, I can add this joint and skin wave it to the base mesh and use that as the basis for my control.
And, this is not at all uncommon. I've done this with many characters too. But, if we're going for a blend shape based set up, it can be very nice to have the jar open shape be a morph target rather than something that is connected to the skeletal hierarchy. So, in order to create the shape, I'm going to switch to the orthographic side view. And, I'm just going to drop in some joints, which I can use to then deform this geometry. You can create joints by going to the animation shelf, or by going to the Skeleton menu in the animation module, and choosing the joint tool.
I'll create a joint at the neck that is just going to be a base joint that I'll use to hold values that aren't being affected by the jaw joint. Then, I'll select a joint at the jaw, it's important that this joint be carefully placed so that it is a reasonable rotation point for the jaw. And, I'll create a third joint for the tip of the jaw. It's a good idea always to name your joints, it really makes skin weighting a lot easier and it's just good practice for organizing your scene. So, I'm going to call this base joint, I'm going to call this jaw joint, and I'll call this one jaw tip.
To connect the jaw joints to the mesh, I'll select them one at a time holding the shift key down to add to the selection each time. And then, I'll select the head mesh and go to skin, bind skin, smooth bind options. The smooth bind options are very important and can dramatically affect the process of painting skin waves on the character. So, I always use the following settings. Apart from the default settings, I set the bind to option to selected joints. This ensures that only the joints that I have chosen are going to affect the selected mesh.
Next, I want to make sure that the skinning method is set to classic linear. This is the default setting, one of the older ones. It also happens to be most compatible with other game engines, and has a very straightforward workflow. Leaving normalized weights set to interactive is extremely important. This will ensure that the collective influence of the joints never exceeds 100%. And, it's going to keep the vertices of the mesh from exploding or behaving erratically when the mesh is moving around. And finally, I want to make sure that maintain max influences is set to off.
This will allow me to paint zero values on certain areas of the mesh to make sure that the joint doesn't influence those vertices in any way. With the settings in place, I'll click apply and test the skinning. I'll select the rotate tool and rotate the joint and we can see that the default skinning is not very good. It almost always requires additional skin weight painting. But, before I move on to skin weight painting, I usually like to set a couple sample key frames that will help me see with more clarity where the problem spots in the weighting are going to be. I'll select the jaw joint, making sure that it's rotation values are zeroed in their initial state and hit the S key to lay a key frame down on the time line.
I'll then scrub to a different location on the time slider. Rotate the jaw joint open, and hit S again to create a second keyframe. Now, I can select the mesh and begin painting and refining skin weights. I'm going to move back to my perspective view, and in order to paint skin weights, I'll go to the Skin> Edit Smooth Skin> Paint Skin Weights Tool> Options. This will bring up another artist and style menu, very similar to the one that we were using for painting Cluster and Blend Shape influences earlier. Once again, we can modify the brush shape by holding down the b key.
And, if we select the different joints, we'll see their areas of influence on the mesh. Areas in white are being affected by the joint. Areas in black are unaffected by the selected joint. As a starting point I'm going to select the base joint and flood with 100% opacity. And, my Paint operations set to Replace with a value of one, full weight of the base joint onto the whole mesh. This will ensure that I have full control over which joints are affecting various areas of my mesh. Next, I'll scroll back up, select the jaw joint.
Scroll back down again and with a reduced opacity, the value is still set to 1 and the paint operation still set to Replace, I'll begin painting skin weights to activate these verts as the jaw moves. So, I've taken a couple of minutes and painted some skin weights along the jaw joint, and I've focused on one half of the character. With just a couple joints in the character, this doesn't really take too long and I have just been using the replace tool and a little bit of smoothing and now, I want to mirror these skin weights on to the other side of the character.
So, I am going to scrub the time slider back to the initial pose. It's very important when you mirroring skin weights that you go back to your bind pose as a first step. Then we'll go to the skin> edit smooth skin> mirror skin weights options. And, we'll make sure that our mirror skin weight settings are correct. This character was initially placed at the X equals zero location, which means that we can use the mirror skin weights options to mirror the skin weights from the left side of the character to the right or the right side to the left. We'll set the mirror cross option to the Y Z axis.
And then, we'll have the option of mirroring from the positive side, or the negative side. Since I've painted on the positive side, I'll make sure the positive to negative check box is active. I'll click apply, and now we can see the right side of mesh is receiving symmetrical influences. For any of these problem areas, we can easily go in and correct them manually by returning to the skin weight painting tool. I'll select the mesh, right click and choose paint skin weights tool to return to skin weighting. With the problem vert selected, I can simply flood those areas with more influence from the jaw and then go back in and make adjustments to the rest of the mesh using the replace and smooth tool as needed.
As I make these additional changes, I'll probably want to ensure that I have symmetry afterwards. So again, I will scrub back to my initial bind pose, select the mesh. Choose Skin> Edit Smooth Skin> Mirror Skin Weights once again to ensure that the skin weights are fully symmetrical. With the skin weights painted, I can now use this mesh as a morph target. I'll select the mesh. Select my starting neutral mesh. Go to Create Defamers and choose Blend Shape and you can test it out. At this point the history on this object could be deleted along with the helper joints.
But, I usually try to preserve these joints until I am absolutely finished with the rigging process just in case I'd like to make additional changes. Like standard clustered formers, Myas joints and skin clusters allows the user to easily manipulate a large selection of vertices from a joint precisely placed pivot location. And, because the skin painting workflow is so familiar to Rigors and offers unique mirroring capabilities, simple skeletons can be incredibly useful as you begin producing challenging targets for our blend shape library.
- 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