View Full Version : RibCage solution

10 October 2003, 06:37 PM
Hello! Hope any of you can help me out here. I am building a skeleton in Maya which will serve as natural moving organism's bindingbasis (hm, I hope that makes sense).

Uptill now everything went smooth, arms and legs work ok, spline works very nice as well. So basicly all good 'till I reached the Ribcage. I can't seem to be able to find a way to rig the ribcage properly.
The ribs have been parented to the backsplinebones, but obviousely they should be constraint bij the sternum (chestplate). The chestplate should move accordingly to the movement of the spine, but after a lot of playing arround with IK's and constraint I still have a sternum living a life by itself and ribs flying all over the place. I am obviousely doing things very wrong here.

Funny enough there does not seem te be too much literature on ribcage rigging arround on the web or in the real world (or I just can't find it).

So therefore I'm here, begging: What am I doing wrong? How should I go about it?

Pic to show what is going on:
(the blue ribs dislocate from the red sternum when the skeleton is bending or stretching)

10 October 2003, 03:26 PM
I would just make life easier and delete them......

10 October 2003, 10:22 PM
mmh, yes. I could of course make life even more easy and not bother at all about making anything, but somehow a human being wants to learn as well. Well, that is to say, some of them.

10 October 2003, 12:58 AM
The way I see it yo have two ways of doing this.

1) Attach the ribs to the back bones by a latice.

2) Create actual Maya joints that go all the way to the sternum, and group the ribs to the Maya bones.

3) Constrain the end of the ribs to the sternum.

This is what I can thinck of right now off the top of my head. I will try to look at my old model and tell you how I did it.

P.S.> No ones back, bends back that far....

10 October 2003, 11:55 AM
You may have seen it already but

Look at the character setup and you will see how the ribcage was done.

Hope it helps.


10 October 2003, 03:17 AM
i have a simular problem, aalthough i've found no real problem riggin my ribcage i have had difficulty animating it. I'm manualy animating a cloth on my character (tunic.. a la generic 2d character) On one of the ribs, on it's translate x function, the coordinates keep jumping to numbers like 2246015.21. Fairly stressing as i have to get this scene shot for monday. Of course i can FIX this manually, but it's already a manual process.. thus spiraling my workflow into the eight ring of hell. Literally, satan is gnawing on my head at this very moment.

10 October 2003, 06:01 AM
Thanks for the feedback guys,

nottoshabi : I thought of the lattice solution, but in that case I would deform the polygonal structure of the ribs, would still have a lot of tweaking to do to get a believable result and it would be a method less physically accurate and overall too different from the rest of my setup for my likeing.
I tried to work with ik-ing joints per rib and constraining them to the sternum, but could not get a proper result. the ribs would flip oncontrolably and the ends of the ribs would still detach when the ik was pulled too far. I still think in theory there should be possibilities in that method and in my tiredness of it all I missed obvious solutions. So I will go back and try again later.

O yes I am aware that no back bends that far, but this illustrated the problem a bit better and I want to keep the option of stretched and over the top animation.

El-d: Yes in the Maya specific forum this one came up and it's great in all sorts of ways. It's definately a method that is in line with what I want to do since it places the logical working of the skeleton first. I'm studying the whole at this moment. It has allready helped me to a better functioning shoulderblade. I can't say it will help the ribcage at this moment since I'm still in the middle of it, but if it does I'll come back to that later.

munky_quack: you say your problem is not to do with the rig of your ribcage, mine is. So I'm sorry but I fail to see the simularity in problem. It would therefore probably serve the clarity of discussion to post your problem seperately from mine.

10 October 2003, 11:54 AM
okay what? so in the future i should think twice before askin help... okay, dutifully noted

10 October 2003, 01:40 PM
Well, I animated an esqueleton and my solution was lattice deformed.
First, after red a lot of anatomy books I realised that the ribcage doesnīt move too much, it only breaths and turns around a little bit, but no more, in real life you canīt rotate that part of the column..., so a lattice works pretty well, only deforms a little (in order to be realistic).
So you have to realise first that a human canīt make those sort of movements, and then rig your ribcage according to that.

Hope it helps.

You can find an example animation here:


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