View Full Version : Arm Rigging Problem 2

06 June 2003, 05:47 AM
Question: I'm using ElectricImage Universe. I don't know if it's the way I rigged, the program, my lack of knowledge, or lack of constraints, but I get a little pop when I extend the IK arms fully straight. Just a small snap as it's locks into the elbow joint.

It's there a general way I can avoid this? Like do you bind to skin with elbows slightly bent or should It be straight? Or maybe I should have a viscosity, limitation or stiffiness value to the elbow. Do I just avoid going extending the arm completely straight?

06 June 2003, 12:02 AM
Try setting the constraints so that you can't fully extend the elbow 180 degrees.

I don't know about every program, but I set up the constraints and IK for any joint while they are *not* resting at full, 180 degree stretch.

You get your pop when the IK is having trouble solving for a straight line, I believe.

06 June 2003, 10:13 AM
You could do what webfox suggested, but attach the geometry to the bones so that when the arm/bones are extended aprox. 178 degrees (just before it would pop), the geometry looks like it's extended 180 degrees or slightly more.

If it makes you feel any better, Maya has the exact same problem. :-)


06 June 2003, 11:40 AM
Wow, this is a great help Folx.

I will set a constraint and now, I know to definitely not to bind the skin while at 180. I didn't but I had consider it an option to reduce the pop.

Yes, I definitely helps knowing Maya has the same problem. This tells me my approach of just learning how to get simple rig practices down in a program I am familiar with will help me when I do start using Maya.


06 June 2003, 11:53 PM
regardless of package, this artifact is usually attributed to the end effector's function curve, usually set to spline, being left as-is with no user tweaking. It's just obeying the curve. Fix that and you'll fix your pop.

06 June 2003, 11:55 PM
BTW nix on restricting elbow's z rotation. If you look at your own, you'll see -z rotation. If a real elbow does that, your cg elbow should too.

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