CGTalk - Popping IK animation

View Full Version : Popping IK animation

L0rd

12-17-2003, 09:14 AM

I'm desparately trying to get a chain (metal) to animate properly using a series of link objects parented to the bones in an IK chain.
The result I'm trying to achieve is that of the chain being pulled tight from both ends.
I've set up numerous rigs to get what I'm after, they all work to a point, but in some places the joints start popping, usually where there is subtle movement.

It's really infuriating.

The chain has to break at a point in the animation. The most successful rig so far is to use 2 IK heirarches, both of which start in the middle, the Root bones are in turn linked to the same central control bone, so that the two sides of the chain can fall away from each other.

+ - - - - . - . - - - - +

Animating it is a combination of moving the two Goal objects at either end and the central ctrl bone.

Like I said everyhting works fine to a point and then I start getting some popping.

Can anyone help me with this please?
I'd appreciate it so much.

Hope this all makes sense.

Cheers,

Lord

policarpo

12-17-2003, 09:17 AM

please post a sample of your animation so we can see what the problem is in the context of the animation.

thanks.

T4D

12-17-2003, 09:28 AM

Have you played with the IK Stiffness setting in the Motion panel ?

also add more then one goal object to the Ik Chain
with lower Goal Strenght then the Main Goal Object
You can get a sort of Spline IK this way.

Post some more details if theseidea don't work :)

L0rd

12-17-2003, 09:44 AM

I'll see what I can do, I might have to wait till tomorrow before I can post an animation.

Desperately need some sleeping.

L0rd

12-17-2003, 10:12 AM

Yeah I had a bit of a fiddle with the IK stiffness, took it all the way down to zero, should I be increasing it maybe?

Anyways heres a crude animation of what I mean, you can see the unwanted jumpy popping mostly at the start.

http://www.oneglasseye.co.nz/otherstuff/chain_a.mov

And images of the rig as well

http://www.oneglasseye.co.nz/otherstuff/chainRig.jpg

Cheers,

Lord

T4D

12-17-2003, 10:53 AM

OK here's afew things from the top of my head ( there isn't much there so here it comes :) )

wind the IK stiffness up on the end ones with the popping Bones even set some Basic limits
Also instead of having IK controling all the channels
Only let IK Control Heading and Pitch NO BANK

If still Not working
Add a null, parent it to the second Or the End bone ( with parent in place turn OFF then turn Parent in place ON re-parent the null to a base null So it's not messing with you IK but is perfectly in position

Now set the Main Ik Null Strength to 100 and the helper Nulls IK to 10 or 20 something small ( Full time IK ON But No Match Goal Oriention )

now the end bones will be trying point at the Little end Goals as well the Main IK target this should smooth things out

Post your progress I might have some Ideas in my head :hmm:

L0rd

12-18-2003, 07:28 AM

Hey T4D, seems to work stiffening the joints, though I'd like them to have more fluidity, which obviously is contrary to stiffening. It will do for the time being.

Cheers,

Lord

kretin

12-18-2003, 08:40 AM

You'll generally find popping when bones don't know exactly where they're sposed to be. One solution would be to include a secondary null, as T4D suggested, but I'd put it in the middle of each chain, with the 4th bone in each chain using the new null as a goal, and as T4D said, low strength. If you keep those nulls down low, the chain will know better where you want it's links to be. You can animate those nulls, but think of them as a general guide for the chain's to bend towards.

Using a second goal you should be able to keep the stiffness at 1 for all the bones.

CGTalk Moderation

01-16-2006, 11:00 PM

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.