kinkie Knees

[mberglund]

if you post the file, i can tell you whats wrong. save it as a .ma.

[carsonmorton]

sorry, i wont be allowed to send the actual file because it's for work. but if you've seen this happen before you might be able to tell me without the file.

really, the actually leg rig isn't anything special. It's got an IK handle that's the child of the foot controller, with a pole vector attached.

[edwardG]

Well, it looks like a gimbal issue to me, but it would only make sense to me if you were using a broken heirarchy or bendy legs.

I agree that it would probably go more smoothly if I had a copy of the file, but I understand why you can't release it.

Here's some possible solutions:

Check the pivot point on the knee Pole Vector control. If it was snapped onto the knee joint then perhaps that is the issue.

It is really interesting to me that the calf wigs out but the knee doesn't. I'm going to assume that you're using 2 joints for the knee, is that correct? If both of those knees are in the same heirarchy, then you shouldn't have put the IK handle from the hip to the ankle. If it's calculating 4 bones for the IK then it might not work properly (IK handles work best on chains with 3 joints). If you are using 4 bones, I would instead make the 2nd knee joint a child of the 1st knee joint, and also make the ankle joint a child of the 1st knee joint. Then you can do some constraints on that second knee joint to make it rotate properly.

Can you show a video with the joints?

[carsonmorton]

I've stripped everything from the rig that doesn't need to be there. the bone still does the same thing. the Knee controller was snapped to the knee joint using the move tool while holding the v key. it's axis match world axis. there is also only one joint in the knee. I've never had luck attaching pics, but i'll try again.http://2.bp.blogspot.com/_iAeNUA-A2g4/SNQZ_7f0sJI/AAAAAAAAAJA/FcGAvDSqEtc/s1600-h/knee.jpg

if it doesn't work go to the blog again
http://carsonsbrain.blogspot.com/

[mberglund]

are you leg joints planer? meaning were they built on a plane? if not you can get weird results. if so you might have to re-do the leg joints build them in side-viewport so you know they are straight and on a plane.

[carsonmorton]

i would have started out with it on a plane. if my memory is correct, then i translated the hip bone over, and then rotated it out (the legs are somewhat splayed out rather than straight down)

i've been doing some experiments with the foot rig, and along the way i may have had to recreate the leg by redrawing the leg joints by snapping them to the old leg in the 3d view... I know i did in the arms, but i'm not sure if i did in the legs.

I'll try to see if that's what happened.

[carsonmorton]

well, it makes me look stupid, but that seems to be the issue. Does anyone actually know why it can't handle being drawn in 3d?

Thanks for your time guys.

[edwardG]

Basically what it's doing is drawing a 2D triangle between the 3 joints you choose, then it's creating an imaginary locator at the knee joint and the ankle joint and doing an aim constraint to the corresponding joints. If the locators aren't in a "straight line" then the calculations get unwanted data on them to begin with and it becomes noticable at "extreme" bends.

One way you can get straight lines is create a polyPlane, line that up inside the leg so that it cooresponds to where the joints would sit in a straight line, and then "make it live" by going to Modify > Make Live. You can now draw the joints on the plane and they will stick to the plane, which is good because they will orient towards each other and give you that perfect "straight line" that I was talking about earlier. Once you're finished, go to Modify > Make Live again to turn off the plane and then you can delete it.

[carsonmorton]

Sweet, I had no idea you could do that polyPlane thing with joints. That's going to be very usefull.


thanks again!

[mberglund]

What I do when i am building a skeleton is use clusters and cv's first. I create a cluster along an edge loop that is in the middle of the, hip, knee, and ankle for example. then I snap CV's to it, to create a curve. From there i move the CV's around until i have them just right, then i snap joints to the CV's. this way the only values you get in the channel box are in translateX (except for the top level joint).

[CGTalk Moderation]

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.