toby

Oh hi there.

IK works perfectly for profile view animations. But every animator knows that characters walking/running directly toward/away from the camera is tough.

Part of that is having to scale the bones instead of just bend the joints. Unfortunately, when I scale the upper leg bone with IK at 100% it starts to rotate for some reason. It rotates when it scales down to about .6 or so.

Anyone else come across this? Work arounds? Solutions?

Thanks!
toby
Posts: 5

Erikari

Hi Toby (:

I can just assume because you didn't post screenshots, but I think that since the IK is always pointing to a bone but in a little chain of two bones, if space is not enough, it starts bending more. Same for the opposite case, if there's more room, it will be straight, I believe once it's straight it doesn't rotate anymore, does it?
What you can do is lower the influence of the IK in the specific part of the animation where you need to scale it, or you just rearrange the IK so it doesn't look like it's moving in the specific frame.

If you need to scale those often, you can consider having a second set of bones children of the leg bones, and you just scale those instead of the ones with IK. I recommend the first solution though.
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Erikari

Erikari
Posts: 551

toby

Sorry about no screenshot. I'm only mean when there's lots of space. Like when the target bone is not touching either of the leg bones.

As shown here...

https://imgur.com/a/w3m3G

...the IK constraint is absolutely at 100 mix.
toby
Posts: 5

Erikari

From the screenshot it looks like the target of the darker leg is the dark foot and not the orange IK target, could you attach this project here?
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Erikari

Erikari
Posts: 551

toby

Ok yes, thank you.

..so on frame 9 of 'run' the upper leg is scaled down. But doing so makes the knee bend.

Hopefully that makes sense.

Regardless, thanks for your time!
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test.spine
IK test rig
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toby
Posts: 5

Erikari

Hey Toby, if you use non-uniform scaling it is possible for this to happen, at first I thought the IK target was the foot, turns out you were right :)
Just try to keep the values similar to avoid this.
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Erikari

Erikari
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