Why is part of mesh deformed by IK Constraints

Question

I have been learning to model characters in Blender for the last week or so and am stuck with my 4th attempt and really don't want to start again when I am close to getting it to do everything it should this time.

My problem is that the waist (torso) area of the character has become deformed since adding IK Constraints for the lower legs. I have had to set the chain length to 2 for these constraints so that when I drag the torso bone up and down again the whole body jumps and lands on the ground naturally (arms and legs behave as expected when jumping) as if the character has jumped by itself.

If I set chain length to any other value other than 2 the waist deformation problem goes away but then the feet don't bounce back when landing on the floor. They goes through the floor instead.

I have tried changing different settings regarding the constraints but no matter what I change I can't keep the effect when landing as it is currently is at 2 and also fix the waist problem.

Any ideas what I can try please?

Link to .blend:

Answer 1

Switching the pole angle to -90 alone will result in the leg bending backwards and breaking knee caps when you play back the animation. To fix that, I added a Limit Rotation Constraint above the IK Constraint for each leg. I found Rotation Limit values (differing for each leg) that allows the frames of animation to look correct without the mesh distorting or bones bending in the wrong direction:

Uploaded the edited .blend here:

This seems like a quick fix, and I would love to hear more experienced rigger tell some preventative measures that you could take to avoid IK twisting issues in Blender.

Answer 2

For the deformed hip this is the solution ...

1. Select your calf bone / lower leg bone
2. Bone Constraints Properties panel
3. Change Pole Angle to -90 degree.

Other Observations Additionally, I have observed that your rig would greatly benefit from collar bones which were missing.