Spiral Galaxy Density

// 023 - Spiral Galaxy Density (space)
// 1:1 Original algorithm engine source
function createGalaxySpiralDensity() {
  const STARS = 2500;
  const starR = new Float32Array(STARS);
  const starTheta = new Float32Array(STARS);
  const starSpeed = new Float32Array(STARS);
  return {
    setup() {
      for (let i = 0; i < STARS; i++) {
        starR[i] = Math.pow(Math.random(), 1.6) * 220 + 8;
        starTheta[i] = Math.random() * Math.PI * 2;
        starSpeed[i] = 0.8 + 0.2 * (starR[i] / 220);
      }
    },
    render(context, timeState, params) {
      const { ctx, width, height } = context;
      const t = timeState.time * Number(params.speed || 0.6);
      const arms = Number(params.armCount || 2);
      const pitch = Number(params.pitchAngle || 0.22);
      const scale = Math.min(width, height) / 500;
      ctx.fillStyle = "rgba(8, 9, 13, 0.2)";
      ctx.fillRect(0, 0, width, height);
      const cx = width * 0.5;
      const cy = height * 0.5;
      ctx.fillStyle = "#ffffff";
      ctx.shadowColor = "#38bdf8";
      ctx.shadowBlur = 24;
      ctx.beginPath();
      ctx.arc(cx, cy, 6 * scale, 0, Math.PI * 2);
      ctx.fill();
      ctx.shadowBlur = 0;
      for (let i = 0; i < STARS; i++) {
        starTheta[i] += starSpeed[i] / (starR[i] * 0.4 + 10) * 0.4;
        const armPhase = 1 / pitch * Math.log(starR[i] / 10) - t * 0.4;
        const distToArm = Math.sin(arms * (starTheta[i] - armPhase));
        const effectiveR = starR[i] * (1 - 0.12 * distToArm);
        const px = cx + Math.cos(starTheta[i]) * effectiveR * scale;
        const py = cy + Math.sin(starTheta[i]) * effectiveR * scale;
        const isArm = distToArm > 0.3;
        const hue = isArm ? (200 + starR[i] * 0.3) % 360 : (270 + starR[i] * 0.4) % 360;
        const alpha = Math.min(1, Math.max(0.15, (1 - starR[i] / 240) * (isArm ? 1 : 0.4)));
        ctx.fillStyle = hsla(hue, 90, 70, alpha);
        ctx.fillRect(px, py, 1.5 * scale, 1.5 * scale);
      }
    }
  };
}

// Default parameters from content metadata
const defaultParams = [
  {
    "key": "armCount",
    "label": "Spiral Arm Count (m)",
    "type": "range",
    "min": 1,
    "max": 6,
    "step": 1,
    "defaultValue": 2,
    "description": "Number of density wave spiral arms"
  },
  {
    "key": "pitchAngle",
    "label": "Arm Pitch Angle",
    "type": "range",
    "min": 0.1,
    "max": 0.5,
    "step": 0.02,
    "defaultValue": 0.22,
    "description": "Logarithmic winding tightness"
  },
  {
    "key": "speed",
    "label": "Pattern Speed (Ωp)",
    "type": "range",
    "min": 0.2,
    "max": 2,
    "step": 0.1,
    "defaultValue": 0.6,
    "description": "Rigid wave pattern rotation"
  }
];

if (!window.__art_instances) window.__art_instances = {};
if (!window.__art_instances['galaxy-spiral-density']) {
  const inst = typeof createGalaxySpiralDensity === 'function' ? createGalaxySpiralDensity() : null;
  if (inst && inst.setup) {
    inst.setup({ ctx, width, height, dpr: 1, aspectRatio: width / height }, defaultParams);
  }
  window.__art_instances['galaxy-spiral-density'] = inst;
}

const instance = window.__art_instances['galaxy-spiral-density'];
if (instance && instance.render) {
  instance.render(
    { ctx, width, height, dpr: 1, aspectRatio: width / height },
    { time, deltaTime: dt, frameCount: Math.floor(time * 60), fps: 60 },
    defaultParams
  );
}