You can either examine those animations in a_ba series and just use them, or you can add a new set directly to the model.
The way I do it is like this:
- Open the text based mdl file of the creature you want to use as a base in one notepad
- Open the text based mdl file of the creature you want to import animations from in another notepad
- In the second file, find the named animation you want to move over to the first file
- Select it and copy that entire named animation to a THIRD notepad for editing
- Check bone names in the copied section against that of the one you want to use as a base. If bone names differ, change them to the corresponding bone name in the base model. Do a find/replace all if needed. If any bones exist in the copied segment which do not exist in the base model, then you need to make a bone in the base model for that animation to work. It will have to be parented in the correct order.
- Now copy that new segment to the bottom of the anims list in the base model.
- Save the new base model as something new.
- Use NwMax to import that new file so it joins the imported animation to the base model.
- Test it in Max to make sure it worked. If not, repeat the process checking for mistakes in bone names.
This process inserts that named animation into the local model, which causes that animation to override that from the a_ba series, if it even existed.
This is not an accurate science, especially if positional keys are used. In addition, if bone lengths are different, you may have issues where like if you want two hands to meet on the hilt of a weapon, what happens instead is they pass through each other, or come nowhere near each other. You'll then need to tweek their frame0 position to make a fit. This can be time consuming.
Animations are in the text files like so:
newanim <animation alias> <model name>
...model nodes here and how they are affected...
doneanim <animation alias> <model name>
Unless they are absolutely needed, you should then remove all position keys which are created on the model. Gmax tends to add positional keys even if you aren't specifically telling it to. These occur almost every time I make rotational keys in Gmax, but for all I know it can be disabled by telling it not to be so absolute. Exceptions are usually just rootdummy type nodes, you want that kept where it is, unless it is not actually used for anything (stays at a fixed point all the time). Everything else should be rotational keys only. I often fail to remove these, even thought I wrote a script to do it for me. Not removing them will cause problems for people trying to use this new model as a supermodel with scale differences.