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Freaky Deaky Bone movement


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Yo

Before I get started, I'm gonna mention that I'm only on AM 2004.

 

I'm trying to set up a bone system similar to thom's balance posing, in his legs. Simple mesh, simple bone system. If anyone knows Thom's leg setup, even better. Basically I have the basic thigh-down mesh controlling bones (thigh, calf, foot, etc), which I'm trying to add at foot/leg-controlling null to. The null is placed at the ankle, and I've added the same bones that Thom has: the thigh aim, knee rotator with rotation limits, and the thigh orientation bone that is supposed to keep the thigh stable and most importantly FACING FOWARD. The first of the three is constrained to aim at the foot controlling null, and the 2 others are it's children. The next move is to 'orient like' the thigh bone to the thigh orientation bone. If you check the Thom model, you can see how the heirarchy allows it to work. I have also kinematically chained the calf to the foot null as well, so that I can control the whole leg with just the null.

**Phew!** Hope youre still with me.

Now I try to move the null to control the leg, and it works fine, until I move it in a certain direction and the thigh bone does an immediate 180 degree flip. This has happened to me before, and usually results in my just completely forgetting about trying to constrain, but here I really want it to work. I figgured that having a 100% orient like constraint used at a different bone that doesnt move so much would stop this from happening, but it doesnt.

 

My 'explanation' (but no solution, haha) is this. When the leg is lifted, the foot comes closer to the hip than it was before. Therefore the bones of the leg cannot stay straight, they naturally must bend. This is nothing new. What I dont understand is why the thigh chooses to solve the motion problem by reverting to the BACK instead of the natural foward motion? I'm going to attach my model so that you can hopefully get a better picture. Most of the setups on the model are tests right now, so no need to comment haha... I'm working from the legs up- that is, unless theyre hindering the leg movement java script:emoticon('B)', 'smid_14')

B)

Oh, in order to check out my problem, you might wanna take a look at the "Nuts and Bolts (basic stuff)" relationship, thats where I'm doing all of this work. As in the Thom model, I used a separate percentage relationship to constrain the hip (or in this case pelvic) null to move and balance the feet. I've tested it and it has no effect on the leg itself, as it was added after the leg problem started (to see if it'd fix it... no.)

 

Thanks to anyone who can help!!!

L

Rig_with_simple_body.zip

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Here is a very good leg tutorial that will probably help. A thigh target and thigh roll target sounds like what you need (I can't check the file at the moment).

 

Hope that helps, Layton.

 

Thats helpful... but.....

The problem is, I already did that stuff... the roll aim bone and whatnot. It still flips! I'm not at home right now, I'm going to try the knee aim thing too later this evening, to see if that fixes it. i'll let you know...

L

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