TYPE: CHOP
TITLE: Attribute CHOP

This CHOP adds, removes or updates attributes of the input CHOP. Currently
there is only one attribute type, a "quaternion". This attribute type is
used to group rotation channel triplets (rx,ry,rz) together. 

Rotations sometimes need to be grouped together since interpolations on
independent X, Y and Z rotations do not produce smooth results. Rotations
often need Quaternion interpolation to rotate through the most direct path.

Operations such as resampling and blending recognize the rotation triplet
with the "quaternion" attribute. They blend or resample the rotation channels
using "spherical linear interpolation". Ordinary interpolation can produce
poor blending results, whereas quaternion blending produces the shortest
rotation path between two sets of rotations.

See some of the CHOPs that use the attribute: the Sequence, Composite and
Interpolate CHOPs. Other CHOPs may quietly use the quaternion attribute, such
as Object, Stretch and Resample.

The Scope is needed to specify the channels that will be grouped.

There are no local variables.

Parameters
Quaternion
    Function     - The function to perform on the attributes:
	Pass Through - Leaves the attributes untouched.
	Replace      - Erases previous attributes and replaces
		       them with the new ones.
	Append       - Keeps previous attributes and combines 
		      them with the new attributes. If an
		      attribute already exists on a channel
		      and append attempts to overwrite it, an
		      error will occur.
	Remove       - Removes all scoped channels' attributes.
    Rotate Order - Sets the rotation order of the rotation triplet. 
    Scope        - Selects which channels are X,Y and Z rotations. The
		   channels can be typed in explicitly, or using wildcards.
		   If the number of X,Y and Z rotations selected do not 
		   match, an error will occur. Example: *r[xyz]
