In CAT, muscles
are non-rendering helper objects that you can use to create a skin
that looks realistic when stretched and deformed.
For example, the following
illustration shows how the Marama rig's shoulder and upper arm have
collapsed after being twisted and pulled in various directions.
(Marama is one of the standard CATRigs included with CAT.)
Marama's shoulder will
behave better once we finish applying the CATMuscle to her CATBones.
That happened because
Marama's rigging includes no muscle objects; the skin shape is determined
by the relative positions of the CATBones.
In the illustration,
the purple patches are the segments of a CATMuscle that was created
and shaped to use as muscles for her pectorals and shoulder. To
complete the job, you would:
- Finish parenting the segments to appropriate
positions on the CATBones.
- Drive the skinning with the CATMuscle
rather than the CATBones.
As the Create panel shows,
you can create two kinds of muscles:
A planar (by default) helper object that is multi-segmented on both
the U and V axes.
A helper object that acts like a Bezier curve between two points.
By default, the muscle strand is shaped like a cylinder that is
thicker in the center and tapers off in size at the ends.
The muscle objects in CAT are
designed to be used in three ways:
- As a set of procedural bone deformers.
When either muscle object is set to Bones mode, you can add it to
Skin modifer like
any other bone. It can also be exported to game engines.
- Both types of muscle objects, when set
to Mesh mode, work well with the
Skin Wrap modifier.
For film and advertising jobs, Skin Wrap often provides superior
performance with high-resolution meshes than does the Skin modifier.
- The CATMuscle object is designed to collide
quickly and efficiently with the Muscle Strand, producing a nice
skin-sliding effect. You could deform your mesh using CATMuscles,
and then set up Muscle Strands underneath the CATMuscles, with the
latter sliding over the strands. The Muscle Strand has controls
for squash and stretch.
A CATMuscle is a non-rendering
multi-segmented helper object that is best used for broad areas,
such as the shoulders and pectorals, that need relatively consistent
stretching and deforming.
- Muscle Strand
A Muscle Strand is a
non-rendering helper object used for skinning characters that acts
like a Bezier curve between two points. Strands provide more precision
than CATMUscles, and give better results when the skin must be twisted.