This is going to be a nice short tutorial on how to add more bones onto an existing skeleton in a way that preserves the animation (useful if you want to add additional bones to the stock male or female human skeleton and don’t want to reexport all its corresponding animations).
First things first, take the existing skeleton (either import it or open it from a save) and add your new bones).
As you can see here, I’ve added 7 bones to the stock male skeleton (breast bone, c L UpperStab, c L ForeStab, c L Stab, c R UpperStab, c R ForeStab, and c R Stab.
Next let’s export it to its new skeleton name, in this case I did s_3_human, select the skeleton option and hit okay.
Now download chunky and use it to open your file, switch to the pivots tab and lets look what’s there.
As you can see, c r UpperStab, c l stab, breastbone, etc. are mixed in with the rest of the bones, unfortunately, we want them at the end of the list. Notice the last bone in the list is “BONE FOR BAG” this one is the key to how we will fix this mess. So back to the editor.
So, what we need to do now is export our skeleton again, this time I’m naming it “original.” Now that that’s done select breast bone, c l UpperStab, c r UpperStab (the base of each of our new bone hierarchies).
Now attach them to “BONE FOR BAG”
Now once again let’s export this to our new skeleton (s_3_human) for me. Don’t save this, you might have to reopen the original depending on how complex the bones you're adding are.
Now open both files, original and s_3_human in chunky (you’ll need to open two copies of chunky).
As you can see now, our 7 bones are now at the end of the file, which means they won’t mess with our existing animations; however, now we need to fix their attachments because right now they're hooked to "Bone For Bag" instead of their proper pivots.
This is easier to do than one might think, simply copy the BASE HIREACHY bones in original (not all of them just the bases) from original and paste them over the bones in s_3_human (in this case just beast bone, c l UpperStab, c r UpperStab).
Now that that’s done, save it and let’s reimport it into our 3d editor and make sure the bones attached correctly.
As you can see, something isn’t quite right, breast bone and the hierarchy for c l UpperStab are fine, but for some reason c r UpperStab’s hierarchy has ended up hooked to c r hand. My assumption is this is caused by the repositioning of so many pivots it wasn’t originally accounting for.
Reopen you’re original file for the 3d model and lets play with what the bones are attached to, in this case we need to move the bone back 3 positions to get it attached to c r clavicle, this took me some guessing but in the end I figured out attaching it to c l UpperStab does the trick.
Now export it over original and reopen it in chunky then copy C R UpperStab from original into your already modified s_3_human, save and reimport.
And ta da, you’ve successfully merged new bones into an existing skeleton in a way that won’t affect the already existing animations!