Quadruped rigging: examples for spine&shoulders?

I’ve googled around but there seems to be no quadruped rigs for blender. There are some for other packages, but I don’t have those.

What I would like to know is how to properly setup spine, shoulders and hips. What is the recommended method for setting up shoulder blades? IK did not work very well over chain length 2 (motion was too extreme at shoulder blades), so I left shoulders out and thought I would animate them separately. Also, where should I parent knee pole targets so that limbs wouldn’t flip at extreme poses? My rig is cartoon-style and simplified at the end of the limbs (no toes, only four deforming bones per limb: shoulder, upper leg, lower leg, hoof). Currently I have leg IK control right before hoof, moving it moves whole leg except shoulder and rotating it rotates hoof’s own IK target, therefore rotating the hoof.

My current method is to deform the character and then reweight problem vertices (those that stick out or in). Is there some better way to fix skinning?

Hi hevonen,

I’ve been at this for 3 days now, and as soon as I think I’ve got most things worked out, I have another issue - I’ve trawled the net too and there’s nothing for blender quadruped rigs except a very basic rig on Blendswap for a dog with no IK or constraints and a complicated rig elsewhere for a real dog, which is obviously overkill for me.

I’m currently having a problem with the IK on the rear legs for some reason, they’re set up the same as the front, but the IK seems to go all over the place from just a small movement before I’ve even attempted a Pole Target.

I still have to do some other parts, but I don’t think they’ll be too much of an issue as it’s cartoon style and I’m more interested in just the walk Cycle, eyes, ears, tail and eyebrow. the eye tracking I have sorted (not in screenshot). Maybe we could share resources unless someone can help?


Here’s the basic rig without Gromit:
http://www.pasteall.org/blend/15898

Jay :wink:

Currently I have leg IK control right before hoof…

Remember that hoof is really a toe or finger equivalent to human anatomy.

I’m more interested in just the walk Cycle…

For walk cycle you will need main mover bone as an overall parent “A”. Next child should be pelvis up / down bone “B”. Leg IK “C” can be setup like human rig but the ankle geometry is different.

http://i1135.photobucket.com/albums/m626/cabby24/Blender%20Pics%201012/duck_rig02.png

The back legs are going crazy because the IK target is a child of the chain that it is trying to control. I.e. Your IK target is a child of the lower leg bone. On the front legs there are two bones that are placed on top of each other. One bone is the IK target and it not a direct child, the other bone is the deform bone for the paw.

Also, where should I parent knee pole targets so that limbs wouldn’t flip at extreme poses?

For my dog rig that I’m working on I have a master root that move everything and rotates around a point between the feet. I have another bone that move everything but rotates around the center of the torso. I’m currently parenting my IK targets and driver bones to this 2nd root bone. That lets me move the entire model around then adjust the pole targets as needed.

I wish I could post a screenshot but I don’t have access to my file right now.

My rig is cartoon-style and simplified at the end of the limbs (no toes, only four deforming bones per limb: shoulder, upper leg, lower leg, hoof). Currently I have leg IK control right before hoof, moving it moves whole leg except shoulder and rotating it rotates hoof’s own IK target, therefore rotating the hoof.

My current method is to deform the character and then reweight problem vertices (those that stick out or in). Is there some better way to fix skinning?

In general, you want to get the weighting set to something that works well for most cases. Then you use shape keys to fix poses that are not working.

Thanks, my rig is intended for realtime use, so I can’t use shape keys. Also polycount is rather limited, making bone deforms tad challenging. Well I have to see what I can come up with.

Are you using second IK chain for scapula-humerus(?) motion? I tried that but it might not be very flexible solution: chain’s IK target is constrained both to main leg target and hips (as copy location from chest, [hips->spine->chest->neck], didn’t do anything). It may also be overtly complicated. Anyway with influence sliders I got shoulder-scapula IK chain to follow main leg motion at half strength so that I’ve single controller for the whole leg.

Now I thought I could have a leg rotation controller for the whole leg near shoulder (in order to rotate IK targets) to get proper arcs, and use IK chains only for ground touches. Is this common approach or even doable?

Ah, I misunderstood what you were saying about “re-weighting” vertices. I think you are doing it the right way. Basically parent the armature, pose the armature, and then adjust the weights to make the mesh follow correctly. It can be challenging to get it to look correct in all cases. In particular, extreme hip and shoulder rotations tend to “crush” the joint or twist it in an unrealistic fashion.

Since you cannot use shape keys, you can try “fan bones” to help with the crushing effects on joints.

Having good mesh topology, aligning edge loops with bone head/tail locations, and putting extra edge loops around joints is also very helpful for controlling these effects.

Are you using second IK chain for scapula-humerus(?) motion?

My rig only has IK on the legs. Lots of shoulder action on my model is not required.

[ I tried that but it might not be very flexible solution: chain’s IK target is constrained both to main leg target and hips (as copy location from chest, [hips->spine->chest->neck], didn’t do anything). It may also be overtly complicated. Anyway with influence sliders I got shoulder-scapula IK chain to follow main leg motion at half strength so that I’ve single controller for the whole leg.

Interesting idea!

Now I thought I could have a leg rotation controller for the whole leg near shoulder (in order to rotate IK targets) to get proper arcs, and use IK chains only for ground touches. Is this common approach or even doable?

I have not seen a rig setup like this but there is no reason why you could not parent the IK target and/or pole to a bone that can easily rotate them in an arc. I think most rigs use a switch so the the arm/leg can be operated in IK or FK mode. If you want smooth arcs then you switch it to FK and do it that way.

I suspect that if you try something like this it will be challenging to get these special rotation bones setup in a good way. At the end of the day the FK bones of the arm are the correct description for FK animation. I think your setup is just going to end up overlapping the FK bones.

Nathan Vegdahl has a tutorial on Rigging a Mammoth on cmivfx.

My Mammoth tutorial is good for learning deformation basics, but I consider it deprecated for learning how to design and build controls: Humane Rigging is much better for that. Granted, I don’t actually show the rigging of a quadruped in Humane Rigging, but IMO that doesn’t really matter: all the things needed for a decent quadruped rig are in there, not to mention that it provides you with much more in-depth training so that you can design/improvise your own rigs in situations where the ones shown are lacking.

What kind of quadruped are you rigging? Shoulder rigs are tricky for animals that lack connected clavicles, because the shoulder blades in such animals are essentially free-floating. Honestly, I’ve not yet come up with a rig for such shoulders that really satisfies me. Up to this point I’ve just used a single bone per shoulder and parented them to the chest, aligning the axes of the bones in a convenient way (and sometimes locking some axes). I’m sure a more sophisticated approach could be taken, but I’ve not yet had much reason to investigate it deeply.

For the spine/hips, I use the same spine/hip rig as for bipeds. I cover that spine rig in Humane Rigging. It is very well suited to both bipeds and quadrupeds.

The other thing that I find tricky about many quadrupeds is the legs. Specifically, if they have 3-segment legs instead of 2-segment legs. For example, the rear legs of dogs and cats. Still struggling with the best way to rig those. So far I’ve just taken to rigging them differently depending on how I expect I’ll need to animate them. But I hope to develop a more all-in-one rig in the future. Alas, I do not have all the answers to rigging.

Here is an example, I have not tested it in any real creature and anatomy probably sucks. But it may smooth leg deformations.

Attachments

foreleg_test1.blend (360 KB)

What I would like to know is how to properly setup spine, shoulders and hips.

Not all the quadrupeds walk and run in same style. But for powerful running they whip their Pelvis forward and back. Lumber between Rib and Pelvis looks almost like spring:

Now the dog run shows not much shoulder flexing. On the other hand there is quite a bit of shoulder movement in Tiger walk:

Here is good image how you can adapt human rig to quadrupeds.

http://hippie.nu/~unicorn/tut/img/basics/animalanatomy/compare-human.jpeg