Partial Orbits

// composition: arc fragments orbiting a pivot at the lower-left thirds crossing, denser near it, opening upward-right
// layering: faint full-travel pencil arcs first, then weighted charcoal fragments, rust accents last
const PALETTE = [
  "#ece6d8", // warm paper
  "#55534d", // charcoal grey
  "#2e2c28", // heavy charcoal
  "#a64b2a", // rust accent
];

const PIVOT = { x: 262, y: 542 };

function arcFragment(radius, startAngle, sweep, brushName, col, weight) {
  brush.set(brushName, col, weight);
  brush.beginShape(0.4);
  const steps = 12;
  for (let s = 0; s <= steps; s++) {
    const a = startAngle + (sweep * s) / steps;
    brush.vertex(
      PIVOT.x + cos(a) * (radius + randomGaussian(0, 1.6)),
      PIVOT.y + sin(a) * (radius + randomGaussian(0, 1.6)),
    );
  }
  brush.endShape(false);
}

function setup() {
  createCanvas(800, 800, WEBGL);
  angleMode(DEGREES);
  brush.scaleBrushes(2.4);
  noLoop();
}

function draw() {
  translate(-width / 2, -height / 2);
  background("#ece6d8");

  // ghost travel: three faint near-complete pencil orbits underneath
  arcFragment(150, -170, 300, "2H", "#55534d", 0.4);
  arcFragment(255, -150, 260, "2H", "#55534d", 0.35);
  arcFragment(360, -120, 200, "2H", "#55534d", 0.3);

  // the fragments: tight and heavy near the pivot, sparse and thin far out
  arcFragment(46, -80, 130, "charcoal", "#2e2c28", 2.6);
  arcFragment(64, 30, 95, "charcoal", "#55534d", 1.9);
  arcFragment(88, -160, 115, "charcoal", "#2e2c28", 2.2);
  arcFragment(112, -55, 70, "2B", "#55534d", 1.5);
  arcFragment(132, 95, 85, "charcoal", "#2e2c28", 1.8);
  arcFragment(158, -120, 60, "2B", "#55534d", 1.2);
  arcFragment(186, -30, 95, "charcoal", "#55534d", 1.6);
  arcFragment(214, -95, 45, "2B", "#55534d", 1.0);
  arcFragment(248, -170, 75, "charcoal", "#2e2c28", 1.4);
  arcFragment(282, -60, 38, "2B", "#55534d", 0.9);
  arcFragment(322, -110, 55, "2B", "#55534d", 0.8);
  arcFragment(368, -85, 30, "2B", "#55534d", 0.7);
  arcFragment(415, -125, 40, "2H", "#55534d", 0.6);
  arcFragment(470, -95, 22, "2H", "#55534d", 0.5);

  // rust: two fragments carry heat, one flake thrown clear
  arcFragment(100, 60, 55, "charcoal", "#a64b2a", 1.8);
  arcFragment(205, -140, 34, "2B", "#a64b2a", 1.2);
  brush.set("2B", "#a64b2a", 1.0);
  brush.line(586, 218, 604, 204);

  // the pivot itself: a small pooled mark, not a bullseye
  brush.noStroke();
  brush.fillBleed(0.5, "out");
  brush.fillTexture(0.6, 0.6);
  brush.fill("#2e2c28", 150);
  brush.circle(PIVOT.x + 3, PIVOT.y - 2, 9, true);
}