The CATUnits Scale value is used throughout 3ds Max CAT to scale the character and its motion to allow sharing between characters. You can adjust it by selecting the CATParent and going to the Modify panel > CATRig Parameters rollout.
Every bone length in a CATRig is multiplied by CATUnits Scale. For example, if a bone length is 3.5 and CATUnits is set to 2.0, then the actual bone length is 7.0.
Also, CATMotion uses CATUnits to scale the size of the motion to fit the rig. The height of the foot lift graph in the CATWindow for CATMotion is also scaled by CATUnits.
If you set CATUnits to 1.0, then all the bone lengths listed on the Modify panel are actual 3ds Max units and CATUnits has no effect on them. Thus you may be tempted to set CATUnits to 1.0 so bone lengths are measured in familiar units.
This is not recommended because CATUnits Scale serves a useful function by providing an approximate size setting for your character. A bigger character should have a larger CATUnits setting than a smaller character.
What this means is that if you need to share animation data between the big character and the small character, 3ds Max CAT can use CATUnits to scale the motion to fit both characters.
When you load an animation clip, an option to scale the data is available. This scaling is calculated using the CATUnits values of the two characters.
In most default rigs, the CATPArent fits comfortably underneath the feet of the character. When building a custom rig, it’s good practice to make the CATParent approximately the same scale relative to the skeleton of your character. The easiest way to do this is to use an existing rig and modify it.
