IK Rig Jittering

[Anonymous]

Hi, guys. I'm hoping that someone has come across this before as this is the first time that I have encountered it after years of using Max.In a nutshell, I have created an IK chain for my model's skeleton. Whenever this IK is manipulated in the Z axis (squatting up and down for example) the leg and feet bones seem to jitter and shake as if the legs were getting very tired. I've recreated the bones in the scene a few times now in varying sizes and I still get this problem. The model (not mine btw) is only 16cm in height so is that the cause? I'm hoping that there is a solution in which I don't have to redo everything and is a simple fix. 

Any help is much appreciated. Thanks, guys.

[leeminardi]

Could it be that the IK Goal is directly above the source thus making the plane of the IK Solver ill-defined?

[Anonymous]

Thanks for the reply. I'm sorry, but I'm not sure what you mean. I select the foot bone > Animation > IK Solvers> HI Solvers >Select the thigh bone. This setup has worked for me every time I've done it up until this model specifically. I have tried other ways like Thigh bone to Foot bone but it still jitters. The IK Goals are in the correct places as usual.

[Anonymous]

I recently encountered IK jitter too - it affected every IK chain in my rig. For me it was a simple fix - I had to select an IK goal, go to the motion panel, and then change the IKHISolver drop-down to IKLimb - I did this individually for each IK goal in my rig and there was no more jitter! I hope this helps!

[lorddavius]

I would not advise to change the IK engine (unless you know what you're doing). The steps I'd follow to solve this problem is:

1 - Check my scene scale.

If you make an IK chain with 16 cm in height and your system units are in meters, you're bound to have issues. The other way also applies - having a big IK chain with a very small system units scale.

Remember that I'm talking about the SYSTEM units, not DISPLAY units. The later is just visual aid for you to model on correct scale, the former is the internal units Max uses to makes all its calculations (from physics to rendering). So change the SYSTEM units with care and with the final deliver and overall scale in mind. I tend to avoid changing it at all.

2 - Make sure your bone chain has some angle to it, as @leeminardi pointed out (see attached image).

3 - You can also play around with the iterations of the IK solver. It usually calculates the IK solution more often (think substeps) and thus provide a better solution when needed.

Just as an exercise, I made an IK leg with 16 cm in height and I can't reproduce the jiggling you have. Maybe you can post your file so we can take a look?

Cheers!

[Anonymous]

Oh thank god, this solved my issues. Cheers friend!