Torso construction (rib cage, spine, pelvis, shoulder girdle)

Building the rib cage, spine, pelvis, and shoulder girdle as solid 3D pieces that lock together and drive the pose, before you add limbs or detail.

What it is

You reduce the torso to a small set of clear, repeatable forms: a rib cage, a pelvis, a spine connecting them, and a shoulder girdle floating on top. You draw them as boxes, barrels, wedges, and arcs, not as outlines of muscle or skin. Each piece has a front, side, and back, and you place it in space with simple perspective.

You start a figure by blocking in these masses. You set the tilt and twist of the rib cage, the counter-tilt of the pelvis, the curve and length of the spine between them, and how the collarbones and shoulder blades sit on the rib cage. The arms, neck, and legs then hang off this structure instead of being guessed into place.

You use this same construction whether copying reference or drawing from imagination: find the rib cage volume inside a photo, drop a simple pelvis shape under it, and check how they relate — is the chest leaning forward while the hips are back, is the spine arched or slumped, are the shoulders lifted or relaxed. Over time your forms may get more stylized, but the underlying 3D logic stays consistent.

Why it matters

Without solid torso construction, figures look rubbery, disconnected, or flat: the chest and hips drift independently, shoulders slide around, and you end up hiding the problems with hair, clothing, or shading. Once you can build and orient the rib cage, pelvis, spine, and shoulder girdle, your poses gain believable weight, your landmarks line up, and adding muscles, clothing, and limbs becomes simpler and more accurate.

You can check it when

• ✓You can quickly block in a torso from any angle using a rib cage form, a pelvis form, a spine, and a clear shoulder line before adding limbs.
• ✓You can show twist and bend by tilting and rotating the rib cage and pelvis separately, connected by a curved spine, without the figure looking broken or boneless.
• ✓Your shoulders and hips consistently show believable opposing tilts in side, front, and 3/4 views, and the spine between them reads as one continuous curve.
• ✓You can lightly indicate collarbones and shoulder blades in different arm positions in a way that still fits your rib cage form instead of floating off it.

Related skills

• Basic mannequin
• Limbs and extremities as simple forms (arms, legs, hands, feet)
• Head and neck construction
• Figure in space (perspective, foreshortening, mental rotation)
• Torso dynamics (directions of torso and pelvis; rib cage–pelvis relationship)
• Weight, balance, and contrapposto
• Axial skeleton (spine, rib cage, pelvis)
• Shoulder girdle (scapula, clavicle)