View Full Version : Jumping bones...

05-07-2005, 03:34 PM
Well, (still being fairly new to LW,) I've been trying to work on a decent rig but have come across a problem when I move them.
When I move the bones around and go to another frame, they...like...jump, a little out of place, especially in the eye bones and limbs. It's really frustrating(!)

I have no clue what's going on...

05-07-2005, 04:36 PM
I checked your scene and made some changes to the leg rig. The problem mainly was that the femur bone was not prebent, so layout did not know what direction you wanted to bend the leg.

I disabled the Follower for the femur bone, and added a second femur bone to control the knee. This way you can use the banking on the femur for IK and just rotate the second bone instead of using follower.

What I've learned from rigging over the years is to keep things as simple as possible and don't use plugins if you can solve the problem without.

I also changed the IK settings for the femur. You might want to add a small bone in between the femur and the pelvis to spread the IK over 2 bones intead of having both IK channels active on one bone which is never a good idea. Always try to use 2D IK as much as possible, layout is not very smart so it can get confused about what channel to rotate on.

I also disabled all limits, if you bend the bones in the direction you prefer on frame 0 you don't need limits.

I hope this will help you out.

good luck

05-07-2005, 05:27 PM
I just recently read in a previous topic in this forum about prebending the leg bones, which is a very good idea, and actually, the leg bones were just ever so slightly bent, which aided me in avoiding any major problems. An extra bone for the knee--I've never heard that one before...

Unfortunately, these, and everything else you mentioned were not the problems I was facing. My problem is after I position the bones, then go to another frame, the bones would slightly reposition themselves a little off from where I previously had them. There are no hidden keyframes, so that's not the problem (I'm not that new to LW :rolleyes: )

I'm stumped.

Here's what I'm talking about, with an arm and an eye example:

05-07-2005, 05:56 PM
ah, sorry. I misunderstood.

I think the problem with the jumping frame has something to do with the arm IK chain ending in the finger, which is a very strange setup. Also not having a "stopper" by setting a bone to "unaffected by IK of Descendents" anywhere in the spine and arm IK chain added to the problem. You need to end the arm IK chain somewhere at the shoulder, or at least before the spine IK starts and end the spine IK chain somewhere. you can use Match Goal Orientation to rotate the hand.

After changing the IK bone from the finger to the R_FA_Joint and setting the LShoulder_1 and Spine_3 " to unaffected by IK of Descendents" the problem was gone.

05-07-2005, 06:51 PM
Hmm...I still have the problem--I'll tinker with the "Unaffected by IK " " a little more.

I still have that issue with the eyes, and don't even know where to begin with that. :(

05-07-2005, 11:47 PM
The easiest way to fix the IK on the legs is to use the joint move tool and pull the knee joint slightly forward of the line between the hips and the ankle.

Your rig overall has got way too many controls. IK is really meant for mainly two things: quick posing and making limbs stick to a surface (like the feet to the ground).

You dont need all the follower stuff you have. I would use IK to control the spine the way youre doing because its very difficult to control. A good rig should be easy to pose and stable while posing and stable as it moves between poses.

Unless the hands need to really stick to a surface I would just use FK on the upper body and IK on the lower body.

You need a better way to keep the feet locked when you pose them. I dont like to use multigoal IK chains because its not typically very stable since you have more then one goal fighting for control over the IK chain. Usually I just use match goal on the ankle bone or orient constraints.

I usually give each eyeball its own layer and add a bone to each eye. Ill parent the eyes to the head bone. The eye bones Ill target to something. :)

05-08-2005, 01:23 AM
Okay, I fixed the eyes for you by changing the head from using a target to IK which works better. Also ended the Right arm IK chain at the shoulder.

As Lary said, try to simplify the rig if you don't have a very good reason to control everything with IK. It feels fancy when you're playing around with the rig, but once you really start animating it will get in the way.

Usualy I only use IK for the legs, sometimes for the head and only for the arms if I need them to stick to something. In fact it's much easyer to get nice movements with FK arms then with IK because you can control if the shoulder drives the arm or if the arm pulls the shoulder by timing the keyframes. With IK that's much harder.

05-09-2005, 05:50 AM
Hah! That's It! Thank's a million!

Oh, and BTW, I wasn't trying to be all fancy schmancy with the complex rigs and stuff, It just happened to be a silly tutorial I followed that ended up giving me a screwy rig...

If it's one thing that never cease to see in this forum, it's "keep things simple." Following the tutorial, I just kinda assumed it was a simple rig. :rolleyes: