Modeling the Arms
The most maneuverable part of the body is the arm. The combined movements of the shoulder girdle, hand, and fingers create an almost unlimited mobility.
The Bones of the Arm
The arm has a similar combination of bones to the leg; one on top and two on the bottom (Figure 6- 20). The most common places where the skeleton of the arm becomes visible on the skin surface are at the top of the arm bone where it meets the collarbone, elbow, wrist joint, and the knuckles.
Unlike the legs, the arms are not built to support the body. Therefore, their bones are slender and their joints are capable of the widest range of motions possible. The ball and socket joint at the shoulder gives the arm the potential to rotate in any direction. The hinge joint at the elbow revolves the lower arm forward. Another hinge joint at the wrist rotates the hand in any direction. One of the forearms can cross the other allowing the hand even greater mobility.
The Muscles of the Arm
Fig. 6-20 Front and back views of the arm bones.
Four main groups form the arm muscles. Two of these are in the upper arm. They control the hinge joint of the elbow. When the arm hangs at the side they can be seen at the front and back (Figure 6- 21).
Two muscles of the top front group connect to the forearm and control its forward rotation. The back group of muscles appear as one when the arm is in a relaxed state. The two groups of forearm muscles operate the wrist joint. Their actions are very intricate because they also twist the forearm and move the fingers.
The muscles in the hands do not influence the shape of the fingers and thumb as much as the skeleton does. Therefore, when modeling the hand, it is important to pay attention to its skeletal form.
Fig. 6-21 Views of the arm muscles.
Modeling the Arm Steps
Step 1 (Figure 6-22). It will be easier if you concentrate on modeling only one arm and then later mirror duplicate it to attach to the opposite side of the body. Find the group of polygons on the side of the torso from which the arm will be bevel extruded. Merge these into one and make the first bevel that forms the shoulder.
Step 2 (Figure 6-23). Bevel the arm polygon all the way to the wrist.
Step 3 (Figure 6-23). Slice in a vertical direction to split the arm up into smaller sections of polygons. Be sure to split the polygons across the elbow joint and once above and below it. Begin to shape the arm by pushing and pulling points.
Step 4 (Figure 6-23). Refine the arm by continuing to move points and splitting polygons where necessary. Add details such as the prominent bones at the elbow and wrist. Make the armpit and shoulder muscle more defined.
Step 5 (Figure 6-23). Mirror duplicate the finished arm and attach it to the other side of the figure.
Fig. 6-22 Arm Steps 1 to 5. 1). Merging polygons between the shoulder and armpit and beveling it out. 2). Beveling the entire length of the arm. 3). Slicing across vertically to create more polygons. Moving points to give the arm a rough shape. 4). Adding details such as the surface characteristics of the elbow and wrist bones. 5). Mirror duplicating the finished arm.