Hello -

is there a simple way to keep the geometry of the feet of an original model and rig from descending below the '0' point of the 'y' axis during, say, a walk cycle? I've tried several rigs built from tutorials and have created an originally built skeleton that works adequately for my needs except for this hitch. While, some rigs work pretty well for this, including the suggestions from Matthew Krick's tuts, I'm hoping there's a simple constraint for the foot bones to solve this.

Also, is there a good tutorial on euler constraints, etc?

First, you are assuming that a character will always be walking on a level surface that doesn't go below "0" on the 'Y' axis. Second, there are several rigs that you can use that can keep the feet from penetrating the ground plane...LiteRig, 2008 Rig, TSM2 and Squetch Rig (the 2001 also, but you're better off going with one of the others listed).

A standard IK leg would keep things under control...here is a good tutorial for rigging a leg.

I'm not sure where there is an euler constraints tutorial...someone else may know.

Hope that helps, Chris.

This sounds more like the problem of not zero-sloping the channels for the feet keys that put it on the ground.

Can you show one of your walk cycles?

attached is a project file with a model and a walk cycle action. This action actually doesn't show the foot problem as obvious as I thought, but notice especially on frames 6 & 30 how the back foot falls under the 'y' axis on the in-between frames while it's on it way from one keyframe to the next. I realize my model is not truly rigged but has a skeleton with some basic cp weighting & smartskinning applied and is lacking toe bones & contols, but it works for my needs right now minus this lowering of the foot problem.

Thanks

I see the problem. Those legs are not rigged, they're just a chain of bones which means you have to animate them in "FK" which will be nearly impossible for a walk.

For what you are doing you want IK legs.

Go to my signature at the bottom of this post, Go to my page of screencam tuts and watch the "Simplest IK leg" tutorial.

Really you should install one of the already-thought-out rigs available on the forum, but watch my tut anyway and see why you do not want to do it the way you are doing it.

The "simplest IK leg" will solve your immediate problem.

Also watch the "Making Bones Stay in Place" video to learn how to zero-slope keyframes.

I'll work through your tuts and see how I fair. I've created IK leg rigs using Matthew Krick's tuts and they work pretty well for me, but sometimes I get some strange 'popping' of joints with the IK rigs I've created. The model as is moves fluidly enough for my needs even without rigging save this foot problem. I know this is just newbie user error, but the software is so deep and the learning curve steep, when I get a model working simply I tend to just hope I can solve some of the immediate small problems, and dive in deeper when I have the time.

Thanks.

Okay - that's a great simple IK leg constraint setup and makes complete sense - thank you! Is the 'hip-bone', as you call it, the same bone as what many other rigs refer to as the 'pelvis'? I have trouble with cp weighting in the leg, hip, stomach areas. I realize the fewer cps you have, the less anomalies occur. How do you weight this area of a biped model? Is there a good tut for that?

It depends completely on your skeleton. In general, you shouldn't have to weight any CPs in this area to more than three bones. Much of the time, you can get away with two bones.

My immediate reaction is to weight the inner spline almost fully to the 'pelvis' and to weight the other cps in varying degrees outward toward the legs, but if there were a good tut to see how a model is succesfully done it would help.

David - the link you provide in your post for a good IK leg rig doesn't load.

In the last part of my vid on Roger's Penguin I get into weighting the legs a bit.

Hmm, it loads for me in Firefox.

Just tried it again and it led me straight to it (in Firefox, which I use as well) - thanks!