What is the advantage of four spine bones instead of three? (VIDEO) (NSFW - slightly nude humanoid)

sr3d

(NSFW - slightly nude humanoid)

I uploaded my three spine bone setup which can be viewed here:

The actual animation test starts @ 0:55 seconds into the video - https://youtu.be/WbkY37Igwe4?t=57

https://www.youtube.com/watch?v=WbkY37Igwe4 - 3dsmax using cat rig

Do you see any problems? If so could you let me know and offer critique on the deformation/bending of the spine bones?

What would be the advantage of using four spine bones instead of three?

musashidan

3 should be fine. Apart from a few minor issues it  looks good. It's great to see you stuck out your earlier CAT frustrations and worked through it.

4 bones would be more useful on an exaggerated,  cartoon rig that would require much more extreme pose-pushing, in my view.

I do see some stray verts on forward bending between breast and top of ribcage. And the peak of the pelvis in front view could use some more blending.

antweiler

More joints = better deformation. This is because the bending is distributed over more transforms, and you get less folding on the skin (and less need for deformation helpers). Think of a sharply bent waterhose or rubbertire.
Skinweights might be more challenging, but thats worth it, imho
EDIT: Your deformation looks good, in your case 3 bones should indeed be ok.

Mark Dygert

Rib cages keep upper spines from being as flexible as lower spines, so you can get away with less spine joints higher in the spine.

Then you have the issue that most games will only let a vert be influenced by 4 bones, when you start factoring in the clavicle bones, the neck and neck twist(s) if you have them you start running into the influence cap.