05Orbiting Satellite Ring Tilting to Follow the Pointer

<main class="stage">
<div class="d3 is-demo" id="d3Root" tabindex="0">
  <canvas class="d3__canvas" id="d3Canvas" width="480" height="300"></canvas>
  <p class="d3__caption">Small shapes have their positions recomputed every frame with spherical coordinates and redrawn in z-order, so the whole ring tilts with the pointer while occlusion still stays correct</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);

.d3 {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $stage-ink;
  outline: none;
}

.d3__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.d3__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 78%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .d3__caption { font-size: 10px; padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .d3 { cursor: default; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.d3 {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #17141a;
  outline: none;
}

.d3__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.d3__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 78%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .d3__caption {
    font-size: 10px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .d3 {
    cursor: default;
  }
}

(function () {
  // 기법: 위성마다 satelliteAngleAt 로 궤도각을 구해 고리 평면(XZ) 위 좌표를 얻은 뒤, 포인터로
  // 정해지는 tiltDeg(최대 ORBIT_TILT_MAX_DEG) 만큼 X축 회전을 적용해 y·z 를 다시 계산한다.
  // 회전 뒤 z값(깊이) 기준으로 zSortSatellites 가 매 프레임 다시 정렬해 뒤에서 앞 순서로 그려야
  // 고리가 기울어도 앞뒤 가림이 맞는다(화가 알고리즘).
  var root = document.getElementById('d3Root');
  var canvas = document.getElementById('d3Canvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  var CALC_W = 160, CALC_H = 100;
  var CX = CALC_W * 0.5, CY = CALC_H * 0.52;
  var RING_RADIUS = 40;
  var ORBIT_TILT_MAX_DEG = 18;
  var SAT_COUNT = 9;
  var ANGULAR_SPEED = 0.00062;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  var rnd = seedRand(429051);
  var palette = ['#6ec8ff', '#b9a0ff', '#ff9ebb', '#4cd4a6', '#ffd23f'];

  var satellites = [];
  for (var i = 0; i < SAT_COUNT; i += 1) {
    satellites.push({
      baseAngle: (Math.PI * 2 / SAT_COUNT) * i + rnd() * 0.3,
      radiusScale: 0.72 + rnd() * 0.32,
      size: 3.2 + rnd() * 3.4,
      color: palette[i % palette.length]
    });
  }

  function satelliteAngleAt(sat, t) {
    return sat.baseAngle + t * ANGULAR_SPEED;
  }

  var tiltDeg = 0, azimuthOffset = 0;
  var pointerActive = false;

  function computeTransformed(sat, t) {
    var ang = satelliteAngleAt(sat, t) + azimuthOffset;
    var r = RING_RADIUS * sat.radiusScale;
    var lx = Math.cos(ang) * r;
    var lz = Math.sin(ang) * r;
    var tiltRad = tiltDeg * Math.PI / 180;
    var ry = -lz * Math.sin(tiltRad);
    var rz = lz * Math.cos(tiltRad);
    return { x: lx, y: ry, z: rz };
  }

  function zSortSatellites(list, t) {
    var withZ = list.map(function (sat) {
      var p = computeTransformed(sat, t);
      return { sat: sat, p: p };
    });
    withZ.sort(function (a, b) { return a.p.z - b.p.z; });
    return withZ;
  }

  var elapsed = 0;
  var cw = 480, ch = 300;

  function drawScene(nowMs) {
    var sx = cw / CALC_W, sy = ch / CALC_H;
    var savg = (sx + sy) / 2;
    ctx.clearRect(0, 0, cw, ch);

    ctx.fillStyle = 'rgba(150,170,255,.14)';
    ctx.beginPath();
    ctx.arc(CX * sx, CY * sy, RING_RADIUS * 0.5 * savg, 0, Math.PI * 2);
    ctx.fill();

    var ordered = zSortSatellites(satellites, nowMs);
    for (var i = 0; i < ordered.length; i += 1) {
      var p = ordered[i].p;
      var sat = ordered[i].sat;
      var perspScale = Math.max(0.55, Math.min(1.5, 1 + p.z / RING_RADIUS * 0.45));
      var alpha = Math.max(0.4, Math.min(1, 0.62 + p.z / RING_RADIUS * 0.4));
      var dx = (CX + p.x) * sx, dy = (CY + p.y) * sy;
      var dr = sat.size * perspScale * savg;
      ctx.globalAlpha = alpha;
      ctx.fillStyle = sat.color;
      ctx.beginPath();
      ctx.arc(dx, dy, dr, 0, Math.PI * 2);
      ctx.fill();
    }
    ctx.globalAlpha = 1;
  }

  function fit() {
    var r = wrap.getBoundingClientRect();
    cw = Math.max(1, Math.round(r.width));
    ch = Math.max(1, Math.round(r.height));
    canvas.width = cw; canvas.height = ch;
    drawScene(elapsed);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) root.classList.remove('is-demo');

  wrap.addEventListener('pointermove', function (e) {
    pointerActive = true;
    var r = wrap.getBoundingClientRect();
    var ny = ((e.clientY - r.top) / r.height - 0.5) * 2;
    var nx = ((e.clientX - r.left) / r.width - 0.5) * 2;
    tiltDeg = Math.max(-ORBIT_TILT_MAX_DEG, Math.min(ORBIT_TILT_MAX_DEG, ny * ORBIT_TILT_MAX_DEG));
    azimuthOffset = nx * 0.9;
    if (reduce) drawScene(elapsed);
  });
  wrap.addEventListener('pointerleave', function () { pointerActive = false; });
  wrap.addEventListener('keydown', function (e) {
    var moved = true;
    if (e.key === 'ArrowUp') tiltDeg = Math.max(-ORBIT_TILT_MAX_DEG, tiltDeg - 3);
    else if (e.key === 'ArrowDown') tiltDeg = Math.min(ORBIT_TILT_MAX_DEG, tiltDeg + 3);
    else if (e.key === 'ArrowLeft') azimuthOffset -= 0.16;
    else if (e.key === 'ArrowRight') azimuthOffset += 0.16;
    else moved = false;
    if (moved) {
      e.preventDefault();
      pointerActive = true;
      if (reduce) drawScene(elapsed);
    }
  });

  function virtualTiltAt(t) {
    return Math.sin(t * 0.00058) * ORBIT_TILT_MAX_DEG;
  }

  var warmSteps = reduce ? 0 : 100;
  for (var w = 0; w < warmSteps; w += 1) {
    elapsed += 20;
    if (!pointerActive) tiltDeg = virtualTiltAt(elapsed);
  }

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!reduce) {
      elapsed += dt;
      if (!pointerActive) tiltDeg = virtualTiltAt(elapsed);
      drawScene(elapsed);
    }
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  drawScene(elapsed);
  requestAnimationFrame(tick);
})();

import { useEffect, useRef } from "react";
import styles from "./Depth3dOrbitRingSatellites.module.scss";

type Satellite = {
  baseAngle: number;
  radiusScale: number;
  size: number;
  color: string;
};

export default function Depth3dOrbitRingSatellites() {
  const rootRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    if (!root || !canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const wrap = canvas.parentElement as HTMLElement;

    const CALC_W = 160, CALC_H = 100;
    const CX = CALC_W * 0.5, CY = CALC_H * 0.52;
    const RING_RADIUS = 40;
    const ORBIT_TILT_MAX_DEG = 18;
    const SAT_COUNT = 9;
    const ANGULAR_SPEED = 0.00062;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const rnd = seedRand(429051);
    const palette = ["#6ec8ff", "#b9a0ff", "#ff9ebb", "#4cd4a6", "#ffd23f"];

    const satellites: Satellite[] = [];
    for (let i = 0; i < SAT_COUNT; i += 1) {
      satellites.push({
        baseAngle: (Math.PI * 2 / SAT_COUNT) * i + rnd() * 0.3,
        radiusScale: 0.72 + rnd() * 0.32,
        size: 3.2 + rnd() * 3.4,
        color: palette[i % palette.length]
      });
    }

    function satelliteAngleAt(sat: Satellite, t: number) {
      return sat.baseAngle + t * ANGULAR_SPEED;
    }

    let tiltDeg = 0, azimuthOffset = 0;
    let pointerActive = false;

    function computeTransformed(sat: Satellite, t: number) {
      const ang = satelliteAngleAt(sat, t) + azimuthOffset;
      const r = RING_RADIUS * sat.radiusScale;
      const lx = Math.cos(ang) * r;
      const lz = Math.sin(ang) * r;
      const tiltRad = tiltDeg * Math.PI / 180;
      const ry = -lz * Math.sin(tiltRad);
      const rz = lz * Math.cos(tiltRad);
      return { x: lx, y: ry, z: rz };
    }

    function zSortSatellites(list: Satellite[], t: number) {
      const withZ = list.map((sat) => ({ sat, p: computeTransformed(sat, t) }));
      withZ.sort((a, b) => a.p.z - b.p.z);
      return withZ;
    }

    let elapsed = 0;
    let cw = 480, ch = 300;

    function drawScene(nowMs: number) {
      const sx = cw / CALC_W, sy = ch / CALC_H;
      const savg = (sx + sy) / 2;
      ctx!.clearRect(0, 0, cw, ch);

      ctx!.fillStyle = "rgba(150,170,255,.14)";
      ctx!.beginPath();
      ctx!.arc(CX * sx, CY * sy, RING_RADIUS * 0.5 * savg, 0, Math.PI * 2);
      ctx!.fill();

      const ordered = zSortSatellites(satellites, nowMs);
      for (let i = 0; i < ordered.length; i += 1) {
        const p = ordered[i].p;
        const sat = ordered[i].sat;
        const perspScale = Math.max(0.55, Math.min(1.5, 1 + p.z / RING_RADIUS * 0.45));
        const alpha = Math.max(0.4, Math.min(1, 0.62 + p.z / RING_RADIUS * 0.4));
        const dx = (CX + p.x) * sx, dy = (CY + p.y) * sy;
        const dr = sat.size * perspScale * savg;
        ctx!.globalAlpha = alpha;
        ctx!.fillStyle = sat.color;
        ctx!.beginPath();
        ctx!.arc(dx, dy, dr, 0, Math.PI * 2);
        ctx!.fill();
      }
      ctx!.globalAlpha = 1;
    }

    function fit() {
      const r = wrap.getBoundingClientRect();
      cw = Math.max(1, Math.round(r.width));
      ch = Math.max(1, Math.round(r.height));
      canvas!.width = cw; canvas!.height = ch;
      drawScene(elapsed);
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) root.classList.remove("is-demo");

    function onPointerMove(e: PointerEvent) {
      pointerActive = true;
      const r = wrap.getBoundingClientRect();
      const ny = ((e.clientY - r.top) / r.height - 0.5) * 2;
      const nx = ((e.clientX - r.left) / r.width - 0.5) * 2;
      tiltDeg = Math.max(-ORBIT_TILT_MAX_DEG, Math.min(ORBIT_TILT_MAX_DEG, ny * ORBIT_TILT_MAX_DEG));
      azimuthOffset = nx * 0.9;
      if (reduce) drawScene(elapsed);
    }
    function onPointerLeave() { pointerActive = false; }
    function onKeydown(e: KeyboardEvent) {
      let moved = true;
      if (e.key === "ArrowUp") tiltDeg = Math.max(-ORBIT_TILT_MAX_DEG, tiltDeg - 3);
      else if (e.key === "ArrowDown") tiltDeg = Math.min(ORBIT_TILT_MAX_DEG, tiltDeg + 3);
      else if (e.key === "ArrowLeft") azimuthOffset -= 0.16;
      else if (e.key === "ArrowRight") azimuthOffset += 0.16;
      else moved = false;
      if (moved) {
        e.preventDefault();
        pointerActive = true;
        if (reduce) drawScene(elapsed);
      }
    }
    wrap.addEventListener("pointermove", onPointerMove);
    wrap.addEventListener("pointerleave", onPointerLeave);
    wrap.addEventListener("keydown", onKeydown);

    function virtualTiltAt(t: number) {
      return Math.sin(t * 0.00058) * ORBIT_TILT_MAX_DEG;
    }

    const warmSteps = reduce ? 0 : 100;
    for (let w = 0; w < warmSteps; w += 1) {
      elapsed += 20;
      if (!pointerActive) tiltDeg = virtualTiltAt(elapsed);
    }

    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min(ts - lastTs, 48);
      lastTs = ts;
      if (!reduce) {
        elapsed += dt;
        if (!pointerActive) tiltDeg = virtualTiltAt(elapsed);
        drawScene(elapsed);
      }
      raf = requestAnimationFrame(tick);
    }
    fit();
    window.addEventListener("resize", fit);
    drawScene(elapsed);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("resize", fit);
      wrap.removeEventListener("pointermove", onPointerMove);
      wrap.removeEventListener("pointerleave", onPointerLeave);
      wrap.removeEventListener("keydown", onKeydown);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.d3} is-demo`} ref={rootRef} tabIndex={0}>
        <canvas className={styles.d3__canvas} ref={canvasRef} width={480} height={300} />
        <p className={styles.d3__caption}>작은 도형들의 위치를 구면 좌표식으로 매 프레임 계산하고 z값 순서로 다시 그려, 포인터 위치에 따라 고리 전체가 기울면서도 앞뒤 가림이 맞는다</p>
      </div>
    </main>
  );
}