Primitive Geometries

Primitive geometries are the building blocks of sketches — lines, arcs, and curves. They follow a "pen" model: each command starts from where the last one ended.

circle

circle() takes a diameter (not radius):

sketch("xy", () => {
    circle(50)                 // diameter 50 at the origin
    circle([30, 20], 40)      // diameter 40 centered at [30, 20]
    circle()                   // default diameter of 40
})

line

sketch("xy", () => {
    line([0, 0], [100, 0])     // from [0,0] to [100,0]
    line([100, 50])            // continues to [100, 50]
    line([0, 0])               // back to start, closing the shape
})

Directional lines

sketch("xy", () => {
    line([0, 0], [50, 0])      // starting point
    vLine(40)                  // vertical: go up 40
    hLine(-50)                 // horizontal: go left 50
    line([0, 0])               // close the shape
})

• hLine(distance) — horizontal line (positive = right, negative = left)
• vLine(distance) — vertical line (positive = up, negative = down)
• aLine(angle, distance) — line at an angle (degrees) for a given distance

sketch("xy", () => {
    line([0, 0], [50, 0])
    aLine(60, 40)              // 60° angle, 40 units long
    line([0, 0])
})

arc

sketch("xy", () => {
    arc(50, 0, 90)             // radius 50, from 0° to 90°
})

Tangent arcs

tArc() draws an arc that is tangent to the previous line or arc — the arc starts in the same direction the pen is currently pointing (shown by the orange arrow in the viewport). This creates smooth, continuous curves:

sketch("front", () => {
    vLine(100)
    tArc(50, 180)              // tangent arc: radius 50, sweep 180°
    tArc(80, -270)             // another tangent arc
})

bezier

Draws bezier curves through control points:

sketch("xy", () => {
    bezier([0, 0], [50, 100], [100, 0])   // quadratic bezier (1 control point)
})

The last point is the endpoint. Points in between are control points:

• 2 points = straight line
• 3 points = quadratic bezier (1 control point)
• 4 points = cubic bezier (2 control points)

Interactive mode

Call bezier() with no arguments to enter interactive mode. Click in the viewport to place control points with a live preview of the curve. Use Ctrl+click to drag existing points, and Escape to undo.