Pose: Boxes, Frustums, and Gesture

"A face barely moves; a body is nothing but movement. So the figure isn't solved — it's stacked, tilted, and swept."

Line of Action First

The figure construction starts not with a box but with a line of action — the single sweeping curve that carries the pose's energy from head to foot. Before any mass is placed, that one line captures whether the figure is reaching, slumping, twisting, or lunging. Gesture comes before structure, because a perfectly-measured figure built on a dead line of action is a mannequin, and a loose figure built on a live one is alive. The engine lays the line of action down first for the same reason a life-drawing teacher makes you draw it in the first ten seconds.

Boxes and Frustums

Onto that line hang the masses. The two big ones — the ribcage box and the pelvis box — establish the torso's twist and tilt, because almost all of a pose's rhythm is the relationship between those two boxes. Then each limb is built as a tapered frustum: a truncated-cone volume, wider at the joint, narrower toward the next, so the arm and leg read as solids in space rather than flat tubes. The whole figure becomes stacked, tilted volumes threaded onto the gesture curve — exactly the articulated construction the previous track promised.

Foreshortening, Read Per Segment

The hardest thing in figure drawing is foreshortening — seeing how much a limb is compressed because it points toward or away from you. So the construction reports it, per segment: each limb frustum carries a readout of how foreshortened it is. That number turns an invisible, feel-it-in-your-gut judgment into something explicit you can check your eye against. It is the figure-drawing analogue of the portrait's pose readout: the engine naming the exact quantity that is hardest to self-assess.

The Exaggeration Dial

Here is where figure work diverges from portrait in spirit. Good gesture drawing lives past literal — you push the tilt, stretch the reach, exaggerate the curve to make the pose read with more life than the flat photo has. So the engine offers an exaggeration dial that pushes the construction beyond the literal fit, meeting you where gesture actually lives. Crucially, this sets up the grader's most humane choice: when it scores your drawing (Track 6), it estimates how much you exaggerated and factors it out, rather than punishing you for the very push that makes a gesture good. Exaggeration is treated as craft, not error.

Code

Figure construction: gesture, masses, volumes, readout·python

# Figure: articulated, so build volumes in pixel space -- no single rigid solve.
loa     = line_of_action(pose_landmarks)       # the sweeping gesture curve, FIRST
ribcage = box_from(pose_landmarks, "ribcage")  # the two big masses set the twist
pelvis  = box_from(pose_landmarks, "pelvis")
limbs   = [taper_frustum(a, b) for a, b in limb_segments(pose_landmarks)]

# Per-segment foreshortening: how compressed each limb is toward the camera.
readout = {seg.name: foreshortening(seg) for seg in limbs}

# An exaggeration dial pushes the construction past literal, where gesture lives.
figure = apply_exaggeration(loa, ribcage, pelvis, limbs, k=exaggeration)
# The grader ESTIMATES this k and factors it out -- it never penalizes it (Track 6).

Exercise

Find a dynamic figure photo — someone mid-stride, reaching, or dancing. Give yourself ten seconds and draw ONLY the line of action: one continuous sweeping line from head through the spine to the weight-bearing foot. No boxes, no limbs. Then look at how much of the pose's energy already lives in that single line, before any structure was added.

Hint

If your line of action is a limp vertical, the pose will read as stiff no matter how carefully you box the ribcage later. A live gesture line has a clear directional sweep and often a curve or an S. The whole figure construction — and the engine's — hangs off getting this one line to carry the movement first.