Rigging... a straight line?


So I wouldn’t think of myself as that terrible using Blender however I’ve come across an embarrassingly simple problem;

I want to rig a cuboid with an elbow-like hinge joint in the centre but I just don’t know where to begin. A simple loop cut in the centre and using two bones merely deforms the shape as seen here.

Using another loop cut close to the original does indeed remove this problem however I’m faced with that fact that as the “forearm” rotates, there is clipping around the hinge as both sections of the mesh overlap. Of course this is problematic…

Any suggestions on what I just couldn’t find the solution to would be much appreciated! Thanks.

Is this supposed to behave like an arm? Try to twist your forearm and watch what happens. The twisting happens all along your forearm, and not in one single place. You can solve this by dividing the forearm in two bones. The one closest to the elbow will just be used for bending the arm. The lower bone will then just be used for twisting.

Then you can add a third bone, which might act as a controller for the other two, using constraints.

If you’re trying to remove the “pinch” from the “elbow,” the usual approach is to add a number of loops around the joint and then weight paint (or otherwise adjust the weights) of the vertices in the joint area so that the influences of the two bones involved is balanced out. The verts on the inside of the joint have to deform in a particular fashion to maintain the volume of the mesh at the bend point – getting this deformation exact is very difficult especially with a large degree of flex. That’s why riggers often use either corrective helper bones that affect only the problematic vertices, or else add driven shape keys that correct for the pinch.