View Full Version : Jittery IK

06-23-2005, 03:35 PM
I'm having problems with an IK chain jittering when my character is a bit of distance away from 0,0,0. The thing is, it's only around 20 meters away, and the jitter is really bad. When I move the character to within a meter of 0,0,0, the jitter goes away completely. I could understand if moving the character hundreds or thousands of meters away caused a bit of innacuracy, but this is a bit rediculous.

What I'd really like to know is this: I've heard about being able to mess with different IK resolution settings by enabling "experimental features", but I can't figure out how to acces these settings. I've enabled experimental features (ctrl-alt-shift F1), but ctrl-alt-shift F3 (which is what I've read is supposed to bring up those settings) does nothing.

Is it different in 8.0 - 8.3, and is there some way to get at these settings?


06-23-2005, 10:13 PM
Okay, I figured it out. it's just ctrl-alt F3. As it turns out, disabling experimental features made the IK stable enough at 20 meters, so problem solved.


06-24-2005, 04:53 AM
Yeah, the settings allow you to mess with the accuracy. The defaults are better for stability, but you can tweak them to make them faster at the cost of stability( As is usual with these type of things)

06-25-2005, 05:32 AM
You can also get jittery issues if you don't terminate the end of your IK chain. ie. If its a leg of a character, make sure you set the hip bone (or equivalent) to 'Unaffected by IK of descendants' to terminate at that point.

I've seen this happen when users leave that off and let LightWave calculate the IK all the way back to whatever the rig is parented to. The further apart things move from that point, the less accurate it gets and you start to get jitters. Usually the first sign of this is extremely long IK link lines in the viewport...

Just 2c on that subject.