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JulianW
05-18-2003, 05:15 AM
Hi,

I've just setup a character using a new rig that I came up with but I seem to be having a small problem with the bones...

In short they aren't staying put with their parent bones. The bones involved are my Hip and Knee bones. Hip is the parent of Knee, and they both have a Goal of matching an associated null's orientation. But the Knee bone doesn't stay attached to the Hip bone!

Does anyone know why it's moving off of position? (their local position doesn't seem to change in value)

cheers,


JW.

PeteS
05-19-2003, 08:08 AM
were you on frame "0" when yo parented?
Did you have parent in place on?

JulianW
05-19-2003, 08:29 AM
Hi,

yup, it was all properly parented, I checked. If I take off the Match Goal Orientation on the bones then rotate them about then the bones stay connected as you'd expect. Its only when I set them to Match their respective Nulls orientation that the lower leg (bone and all) pops forward by ~10cm on apparently random frames, but seems ok on most frames.

I've managed to re-rig the character a different way now (to take out the Match Goal Orientation and hence the freakish disarticulation of his legs) so its no longer a great issue, it just annoys me when things don't work properly,


JW.

JulianW
05-19-2003, 10:42 AM
Hi,

I've attached a zip with a simplified version of the object and scene if anyone wants to take a look at it and tell me what's up that would be great,

cheers,


JW.

meatycheesyboy
12-06-2003, 03:57 AM
Sorry for bringing back such an old discussion but does anyone know what causes this? I'm having the same problem where bone chains become disconnected but only when I have 'match goal orientation' turned on. As soon as I turn it off, the problem goes away.

I'm using a very basic setup for feet and have match goal turned on for the foot orientation, pretty standard stuff, nothing fancy, but I can't firgure out why this is happening.

SplineGod
12-06-2003, 04:03 AM
Something else may be the issue. Ive used match goal for years on my rigs and I dont recall ever seeing that happen.
I also downloaded the zip file and loaded your scene up. I dont see anything moving away from anything else. Also, the rig just seems generally unstable. Is there a reason you rigged that way?

meatycheesyboy
12-06-2003, 04:31 AM
Here is a picture that shows the problem. I've also attached a scene of my own showing the problem I'm having. If you go to a side view and scrub the timeline back and forth you can see the problem in the right leg.

http://www.jjorg.com/forum/ikprob.gif

SplineGod
12-06-2003, 04:46 AM
Hey Josh,
Your rig does the same thing for me too. VERY strange!
Can you tell me the process you went thru to create the skeleton?
Ive never had this happen to me that I can recall.

meatycheesyboy
12-06-2003, 05:03 AM
Sure,

I created the bones using skelegons in modeler. Converted everything in layout. Reparented certain bones in layout that were incorrectly parented because of the skelegons. Turned on 'unaffected by IK of descendents' for the top bones in the IK chains of the legs. Turned on IK for the heading and pitch of the thigh bone, turned on IK for the pitch of the shin bone. Created a null to be used as the goal. Made the null the goal of the ankle bone, turned on 'full time ik, match goal orientation, and keep goal within reach'. And that's it.

The bone chain is as follows:

LegPivot <----- this bone will control knee pointing, its the one with 'unaffected by IK of descendents' turned on'

UpperLeg <---- this bone has IK for heading and pitch.

LowerLeg <---- this bone has IK for pitch only.

LegEffector <--- this bone is the bone my goal is attched to. Its really really small might be hard to see in the scene.

Foot <---- this is the bone that rotates with the match goal. It isn't part of the actual IK chain.

Toe <--- just a toe bone.

If I take the Leg Effector bone out of the chain, then it works fine. It only messes up when I have that extra bone and I turn on 'match goal orientation'. I'm working on ways to just make do without that bone but I have issues with the match goal angles if I take it out. And even if I do find a solution, I'd like to know what's causing the problem anyways for the future.

SplineGod
12-06-2003, 05:08 AM
Do you get this behavior everytime you rig the same or similar way?

SplineGod
12-06-2003, 05:21 AM
Do you get this behavior everytime you rig the same or similar way?

meatycheesyboy
12-06-2003, 11:21 AM
Sorry it took so long to reply. I had to get some sleep or else I would've been up all night worrying about this problem. Even as it is, I stayed up in bed thinking about things like IK and match goal orientation for waaay to long. :)

I have seen this problem one other time. It was rigging for this same chraacter using the same steps as I did this time. I'm only just now learning to rig so those are pretty much the only times I've tried to rig.

I also forgot to mention, I'm getting alot of info from the froggyplat videos so I'm using local coordinates and I'm recording pivot rotation on all my bones. froggyplat uses a very similar setup in his vids but his sample rigs don't have the same problem.

Thanks for any help you can offer me Spline, and anyone else who jumps in.

In three days if this isn't solved, do I get a "I stumped the SplineGod!" T-shirt? ;)

SplineGod
12-06-2003, 03:15 PM
Originally posted by meatycheesyboy

I have seen this problem one other time. It was rigging for this same chraacter using the same steps as I did this time. I'm only just now learning to rig so those are pretty much the only times I've tried to rig.

I also forgot to mention, I'm getting alot of info from the froggyplat videos so I'm using local coordinates and I'm recording pivot rotation on all my bones. froggyplat uses a very similar setup in his vids but his sample rigs don't have the same problem.

Thanks for any help you can offer me Spline, and anyone else who jumps in.

In three days if this isn't solved, do I get a "I stumped the SplineGod!" T-shirt? ;)
With IK make sure youre working in parent coordinate system. IK by definition takes it orientation from the parent. Working in local coords can really screw you up when setting up IK because IK only works in parent coords. In local coords the rotation handles may appear to be aligned properly and then go wacky because of the parent coord thing I just mentioned.

Using record pivot rotation on every bone is a BAD BAD thing. I would highly recommend NOT doing it. IF you have to it should be used very sparingly. LWs native RPR has problems. This has been fixed in LW8. Its better to fix any bone rotation issues in modeler using bank handles on the skelegons if you can.

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