Hi,
I am currently working on a 3D interactive game including many characters. Yet, I have an issue regarding the animation system.
I made the rigs and animations of my characters on 3DSMax 2014. Then, after importing them on Unity, I have some moving problems around the neck. Moreover, I created a mecanim based controller for all of my characters on Unity.
The issue is that all my characters have 3 boned spines each. While Unity doesn’t seem to support Humanoids with more than 2 bones (one for the Chest, and the other on the Spine), which results in a weird animation, since my second spine bone is always ignored. I can reach those fields from the bones mapping window when configuring a Humanoid set avatar.
I would like to know if there could be any solution or workaround that will make me be able to put one more bone on the spine since I can’t use Generic animation type on my characters ?
Unfortunately, it will be a hellish solution for my new project to have to go back and do again all animations and rigging… So I would be grateful if you could be of any help.
Thank you in advance for your help.
Well you can try adjusting the muscle rig to achieve whatever you need, but that takes a lot of trial and error; a PITA 
I’m not sure if the following will help ease the pain a bit:
Why can’t you use Generic? If you made the models, and you made all the animations, then what is the point of using the Humanoid rig?
I agree with medhue - again. 
Unless he animated different cycles on different characters. Then he’d need humanoid to retarget.
Can’t you assign the upper bone to the humanoid upper bone and the lower bone to the humanoid lower bone and everything interpolate correctly?
About the neck
2 reasons for the skinning errors, either there are more than 4 bones effecting some of the verts. Unity only allows up to 4 bones per vertex. Fix the blended verts and re-export.
Or you used the biped system, and you used the default neck setup instead of the triangle neck. This can be switched in the biped structure roll out, without any modifications made to your animations. You may have to edit some of the animations if you animate the neck a lot in different cycles, but I never experienced any oddities from switching this after creating several animation cycles.
I also remember reading - Max 2014 fbx export isn’t as solid as 2012. May want to attempt a 2012 export just to see if it helps.
In the future it’s best to take your first character into Unity to see the edits needed before creating a whole army of characters. 