View Full Version : Trouble with IK

12 December 2001, 05:45 PM
Hello everybody, I'm having some trouble with my IK and was hoping one of you "pro" guys could help me out.
I have just created IK on my new character and is ready to animate, but when I rotated him, the IK doesent seem to work very well. Can anybody help me out here ?

12 December 2001, 05:58 PM
Could you post the scene anywhere? It's hard to tell from your post what the problem might be.

Best wishes


12 December 2001, 06:25 PM
Here is two scenes , if you could help me out here, testanimation is working out nice, but test3animation isn't working properly.
but the IK is exactly the same...

12 December 2001, 08:28 PM
Originally posted by jornkk
Here is two scenes , if you could help me out here, testanimation is working out nice, but test3animation isn't working properly.
but the IK is exactly the same...

I couldn't get the test3animation because of some extra files it wants to find which aren't

included in the zip file. (Try using con man to export the scene and it's entire file structure to a new directory and then rezip that so all the scene contents will be included the next time

you want others to try your scene.)

The "testanimation scene" has a few problems that you can try to adress if you want better ik performance and a workable skeletal rig for a biped.

First scale the object you have to a real world dimension. Right now the character is

around 17 meters tall. (approx 50 feet tall) Lightwave's IK doesn't work well with huge

objects for some reason. Goal strength settings tend to become counter intuitive and

instead of requiring larger number settings to achieve stronger goal strengths, you will

need to input decimals to achieve more goal strength. So go back into modeler and scale

the geometry down to about 2 meters tall. I'd recommend using skelegons so you can rescale you characters easily and also have a skeletal rig you can easily reuse for other bipeds with a bit of adjusting by copying and pasting within modeler.

Secondly, you need a few more bones in your skeletal rig for control of hip swivel and

shoulder pitch. Your current skeleton has the hip bones connected directly to your root

bone and that's not good. From your root bone create a very small child bone(call it

dummy waist bone) that travels down the -y axis, next create another very small child

from that bone that travels along the -z axis and call it hip pivot bone. Now create

your hip bones from that last bone you created.

When you animate your character you will animate the roll of the hips using FK on that

"hip pivot bone" Don't bother trying to use IK for the hip roll until you get the basics

on biped animation figured out.

You also need to add a pivot bone to your character's shoulder by adding a very small

bone in the -z axis which you then use to build your shoulders off of. That bone will

let you roll the shoulders using FK also.

Lastly, you need to set the hip bones under the motions menu to have the "Unaffected by

IK of Descendants" option checked/selected. This will keep your hip from folding like a

hinge on itself and also eliminate unnecessary IK solving calculations.

There are a many, many ways to rig a skeletal setup and these few ideas should help with

the basic rig you have going. I'd recommend adding more nulls to your rig for more control.

For example, make a master null that you parent your body geometry to and use that to

animate the basic position of the body instead of animating the body geometry directly.

Also add a master ankle null that you parent both ankle's to so that you can move both

ankles in the y axis simultaneously. You can easily go further with more nulls from there but maybe you get the idea.

Good luck!

12 December 2001, 10:11 PM
Thank you very much for taking your time to help me out here.
I guess I still have a lot to learn about rigging a character :)

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