My Rigged Model is Going Crazy!!

AlmondShepard

I'm really new to Maya so I have no idea what I'm doing. I've imported an obj from sculptris and I've made a skeleton and bound the skin but when I try to move the model it goes nuts! Below is a picture of me trying to move the knee joint. Seeing as I don't know anything it's probably a really simple solution but I can't find it. Any help for a noob would be greatly appreciated.

Zitch

Maybe a video of you moving it would make it easier to see the issue.   It just looks like that you have weight set to another joint. If you are not locking your joints and you paint negative values, it will assign those lost values to random joints that are unlocked.

kwyjibo

From your screenshot, it appears that you're translating the knee joint in space rather than rotating the joints. Thats why the area of the model skinned to the first leg joint is still pointing downward (rather than toward the knee) as it hasn't actually rotated. Also you seem to have weighted too much of the upper leg to the knee joint. Try to think in terms of joints, not bones. You weight vertices to joints which you can think of as pivot points, not actually attaching things to bones.

For something like a leg, you would typically rotate the joints by hand or have them driven by IK. You would never translate them as this is alters the length of the bone as seen in your screenshot. Even for a squash/stretch rig you'd probably only move joints in along x (in maya) in their local space ie. down the length of the bone.