You can edit the 3ds Max Biped template and save your customized templates. Once you save the customized Biped template, it appears in the Asset browser > Characters folder.
Navigate to C:\ > My Documents > MB >
Create a copy of the 3ds Max Biped Template.py file.
Make copies of MotionBuilder software files you wish to edit. Doing so ensures the original files remain intact.
Open the Copy of 3ds Max Biped Template.py file.
In the Windows dialog box, choose the select the program from a list option and click OK.
In the Open With dialog box, choose a Text editor program and disable “Always use the selected program to open this kind of file” and then click OK.
Make your changes to the file.
Save the file through File > Save As. In the Save As dialog select “All Files” from the Save as type drop down menu and give your file name a .py extension.
In the Character Template folder delete the Copy of 3ds Max Biped Template.py file.
The new template appears in the Asset browser > Character asset folder after you restart MotionBuilder.
Characters folder A. Custom template
You can modify the current 3ds Max Biped Template.py script to accommodate a custom skeleton.
Navigate to C:\ > My Documents > MB >
Create a copy of the 3ds Max Biped Template.py file.
Make copies of MotionBuilder software files you wish to edit. Doing so ensures the original files remain intact.
Open the Copy of 3ds Max Biped Template.py file.
At the start of the script, there are three variables that you must modify:
A limitation exists if you merge the same bipeds multiple times into a scene. The MotionBuilder naming scheme conflicts with the 3ds Max Biped Template.py script. To modify the script, all bones must be correctly named without any suffix numbering. The workaround is to activate Apply Namespace from the Merge Options dialog when you merge the same bipeds into a scene. Using the Apply Namespace option prepends a namespace to the bipeds, guaranteeing their uniqueness while their "short name" is correct. See the Namespace area in the Merge Options windows.