How it works
A dropdown picks the shape and each one brings its own controls, but none of them is a picture of a cactus or a hand. What a shape hands back is a list of coordinates in its own units — a trunk profile, a shoulder curve, a half-width along a leaf’s spine — and everything after that is shared: measure what came back, drop it into the cell, and draw it. So the sketch has no idea what it is drawing, and an eighth shape is one function and one line in a list.
What every shape hands back is exactly one closed loop, and that is the rule the whole piece is built around. A silhouette is an edge and nothing else — there is no second contour anywhere inside the first, no hairline across a head, no ring inside a circle. It is a real constraint rather than a stylistic one, because an outline cannot show one thing standing in front of another; it can only show their union. So the hair is part of the head’s own profile rather than a shape behind it, and the mountain has foothills set down into its valleys rather than ranges stacked one behind the next, since a range behind a range is precisely the thing a single line has no way to say.
Two of the shapes are not one outline but several parts, and joining them is the only real problem here. A cactus is a column with arms; a hand is a palm with fingers. Rather than union the parts as areas, each limb is grown from a centreline into an outline of its own, and then spliced into the body by list surgery: walk the body’s closed polyline, find the two points where the limb crosses out of it, throw away the part of the limb that was inside, and replace the stretch of body between those crossings with what is left. Both crossings are worked out exactly, so the seam is watertight — one unbroken line, with no union algorithm and no grid whose resolution you can see in the corners.
The shape can be left as a bare line, filled flat, or filled with a gradient between two colours of the palette — and the gradient is the part with no shortcut. A print file re-runs the sketch against a recorder that writes vector paths, where there is no gradient to ask for, no image to draw and no pixel to read. So it is built: the silhouette is sliced across the gradient’s direction and each slice filled flat, which is how a screenprint would arrive at one anyway. The slices are trapezoids taking the shape’s own width at each end, so a sloping edge stays sloping rather than becoming a staircase; where the two ends disagree about how many spans there are — a slice holding the notch where two fingers part — it halves itself and tries again. An angled gradient turns the shape until the slicing is level, then turns every slice back.
That splice is also what the constraints are for. It knows how to keep a limb from colliding with the body and nothing else, so two arms overlapping would be two outlines crossing in mid-air: each arm is given a ceiling at the next one up its own side, and one with no room left is dropped rather than squashed. The line is finally pushed off true by two octaves of noise — a slow wander of a few hundred pixels and a fine tremble of fifty — cross-faded back into itself where the loop closes, which is the difference between a drawn line and a plotted one.