Research & Development for 3D & the Web

To get surfaces to deform as you move joints, you must bind them to the skeleton. There are many skinning techniques in Maya to bind a surface. This page will look at a few of them.

Parent Binding:

Probably the simplest type of binding is just to parent geometry to joints. This doesn’t require any tweaking, but does require the pieces of your model to be separate, eg. 2 rectangles which are detached from each other. Some other examples where parenting is appropriate is a ring on a finger or the eyes on a character.

To parent geometry, firstly click on the left geometry object, then Shift-select the left bone (in that order) and press the “p” hot key to Parent the geometry object to the bone.

Rigid Binding:

Rigid binding works basically like the parenting method, except on the geometry’s components. By rigid binding geometry on bones, the verticies closer to a certain bone will be instructed to follow that bone. This type of binding usually looks good on low res poly models or NURBS surfaces, but can cause cracking on dense models.

Flexors:

Flexors are a type of deformer designed to be used with rigid bound surfaces. By creating a flexor for a joint, you can smooth out the binding region betwen two bones thus breventing geometry from cracking. Flexor points can also be driven by Set Driven Keys to modify their positions as the bone rotates. For instance, you can refind an elbow shape when the elbow is folded.

Creating Flexors:

Select the joint you wish to modify and go to Skin > Edit Rigid Skin > Create Flexor…

Make sure the Flexor Type is set to Lattice and turn On the Position the Flexor checkbox. Click Create. You can then translate and scale the flexor to cover the bending region.

Using Set Driven Keys:

Zero out the rotation of the bones. Select Animate > Set Driven Key > Set > [].

In the Driver section, load the joint in question and select Rotate Y (or whatever it might be) attribute. Select the flexor and press F8 to display its points.

Select all the flexor’s lattice points and click the Load Driven button in the Set Driven Key window.

Highlight all the driven objects in the Driven section and highlight the XYZ values on the right side.

Click the Key button to set the normal position.

In the case of an Elbow (as an example), go back in Object mode and rotate the middle joint on the Y-axis by about 80-degrees. Select the Flexor and pres F8 again to display it’s points. Move the flexor points to confer a nice elbow shape to the cylinder. Click the Key button to set the bent position.

Lattice Binding:

Will put notes in later…. Refer to the “Learning Maya 7″ text on page 386 for now.

Smooth Binding:

The most advanced type of Maya skinning is called ‘Smooth Binding’.

This is a great video (although done in a much earlier version of Maya).