The Advanced Art of Stop-Motion Animation: Building Puppets: Part 2
When designing joints like these, it is important to think ahead to the actual animation and motion that are required, in terms of which joints need to move forward and backward, up and down, or any range of diagonal movement. Ball joints typically provide a great range of circular movement compared to hinge joints, which typically only have lateral movement up and down, like a knee or elbow. In the close-up detail of Charlie’s torso (Figure 3.37), there are three U-shaped joints: one for each shoulder and a middle one for the neck. These joints are the anatomical equivalent of the clavicle and the point where the neck joins the spine. The range of movement for these ball joints is mostly left/right or up/down, which allows for tilts of the head and shrugs of the shoulders. The location of the plates in relation to the rod means a small amount of forward/backward motion is possible. However, there is more freedom of movement allowed for in the joints on the other end of the rod, which provides additional mobility for his neck and shoulders. The same principles of motion are applied to the leg joints, based on how they should be able to move (Figure 3.38). When the parameters of movement are specified in terms of the amount of freedom needed in the animation, these parameters can be applied directly to how the armature is constructed. The more you know about real human anatomy and how real joints are capable of moving, the more informed the armature can be in terms of mimicking this motion for animation. If you have any experience in rigging 3D computer models, you may find some similarities to the necessary constraints of movement involved, but the biggest difference is dealing with real physical materials.
Both puppets’ armatures are covered in foam that is carved into shape to provide the bulk of their bodies. First, two blocks of foam are spray glued to each other around the front and back of the armature (Figure 3.39 and 3.40).