How do you stop knee joints bending backwards


(soletread) #1

I have followed a few tutorials on rigging and I have all but one feature working correctly:

When I raise the foot of a character, its knees bend backward. What constraints are there to prevent this from happening? The tutorials have been really great at helping rig feet that dont slip etc, but nothing about this…

Ok, this problem happens with elbows as well…


(theeth) #2

it’s always a good idea to model the joints slightly bend at first so the deformation will happen in the direction you want it to happen.

Martin


(soletread) #3

Thanks. But its not so much a modelling problem as a bones setup problem. Or so I think.

Is there no way you can prevent the knee from folding backwards by using a constraint of sorts on the skeleton itself. I have seen this done in animation:master and poser, but the systems they use would not work in this instance as Blender has only 4 constraint types, or am I missing something…?

I had limited success by using an empty placed just behind the knee joint and then placed a constraint on the shin bone (not sure what the medical term for this bone is :slight_smile: ) to track to the empty. It works great but when the armature moves the empty stays put. So then try to parent it to the bone or armature, blender crashes. Do the parenting first and then place the constraint and the constraint no longer prevents the knee from folding back…

Cheers


(theeth) #4

When I said modelling, I didn’t only mean the mesh. Try moving the joints of the armature a little off center so as to make it more or less bent in a direction. That is probably the simplest method other than using track to constraints.

Martin


(soletread) #5

Ok cool, thanks…