I’ve developed a race car driver model for a game I’m making, and I gave it bones for animation. The problem is, whenever I position the armature so that the arm crosses in front, the bicep thins out. The picture shows what’s going on, as well as the mesh and bone setup. This is my first rig, so it could be an easy solution.
As you can see, I have thoroughly developed a UV template for this model, so if it is possible that the mesh can stay as is, that would be preferred. If not, I can always go back and re-do the template, no biggie.
There should be at least 3 loop cuts around elbow joint. You only have one!
One cut where elbow bending take place, which you have created, that loop shares the influence of rotation from both arm bone. Unfortunately if you have just one loop, the influence from each bone will be distributed all the way up to shoulder joint and to wrist joint below affecting the whole arm. The effect is blended throughout the arm.
What you want is to limit the blending to where elbow is. Adding extra loop cuts on both side of elbow will ensure to limit the bending influence from each bone. In fact all body parts that bends will need 3 loop cuts.
certainly best having more geometry around the joints in general.
If for some reason the geometry HAS to stay as is, you could create a shape key for each joint in bending pose which scales up the joint vertices. Then use drivers to control them when a lower arm / thigh is being bent…
