08Loader Whose Grid Points Rise Into a Perspective Terrain by Value

<main class="stage">
<div class="ld" id="ld">
  <p class="ld__hint">Click or press the space bar to pause or restart</p>
  <div class="ld__field" id="field" role="application" aria-label="Terrain-grid perspective test panel" tabindex="0">
    <div class="c3__scene">
      <div class="c3__grid" id="grid"></div>
    </div>
    <b class="ld__badge" aria-hidden="true"><span class="ld__badgeNum" id="pct">0%</span><span class="ld__badgeUnit">Progress</span></b>
  </div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 지형 격자 원근 로더 — 격자점마다 고정된(무작위 없음) 높이 가중치를 갖고 있다가, 진행률 값이
// 오르는 비율만큼 각 점의 높이를 끌어올린다. 점들은 카메라와의 거리(Z)가 다른 자리에 미리 배치돼
// 있어 CSS 원근 투영이 가까운 점은 크게, 먼 점은 작게 그려 지형처럼 입체감을 만든다.
// 01(문턱 인덱스 스왑)·02(정점 좌표 보간)·03(연속 순환 랭크)·04(고리별 개별 기울기)·05(구면 중심 수렴)
// ·06(면별 독립 문턱 램프)·07(회전각+거리 깊이 순위) 과 다른 축 — 고정 가중치 필드 값을 원근 투영과 결합한다.

$duration: $dur-loop;
$easing: linear;
$color: $subject-blue-deep;

@include stage($stage-paper);

.ld { display: flex; flex-direction: column; gap: $sp-2; width: 100%; max-width: 360px; }

.ld__hint {
  margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: rgba($subject-ink, .78);
  text-align: center;
}

.ld__field {
  position: relative; height: 208px;
  border-radius: $r-card; overflow: hidden;
  background: $subject-cream;
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  cursor: pointer;
}
.ld__field:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }

.c3__scene { position: absolute; inset: 0; perspective: clamp(280px, 60vw, 420px); }

.c3__grid { position: absolute; left: 50%; top: 62%; width: 0; height: 0; transform-style: preserve-3d; }

.c3__pt {
  position: absolute; left: 0; top: 0;
  width: 7px; height: 7px; margin: -3.5px 0 0 -3.5px;
  border-radius: 50%;
  background: $color;
  will-change: transform;
}

.ld__badge {
  position: absolute; right: $sp-2; top: $sp-2;
  display: flex; align-items: baseline; gap: $sp-1;
  padding: $sp-1 $sp-2; border-radius: $r-pill;
  background: rgba($subject-ink, .78);
  color: $subject-cream; font-weight: 700; font-size: 11px;
}
.ld__badgeNum { font-size: 13px; color: $stage-yellow; }
.ld__badgeUnit { font-weight: 700; }

@media (max-width: 340px) {
  .ld { gap: $sp-1; }
  .ld__field { height: 124px; }
  .ld__badge { font-size: 10px; padding: 0 $sp-1; }
  .ld__badgeNum { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field { cursor: default !important; }
  .ld.is-still .ld__badge { opacity: .92 !important; }
}

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

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

.ld {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 360px;
}

.ld__hint {
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: rgba(23, 20, 26, 0.78);
  text-align: center;
}

.ld__field {
  position: relative;
  height: 208px;
  border-radius: 16px;
  overflow: hidden;
  background: #fff7e6;
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  cursor: pointer;
}

.ld__field:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.c3__scene {
  position: absolute;
  inset: 0;
  perspective: clamp(280px, 60vw, 420px);
}

.c3__grid {
  position: absolute;
  left: 50%;
  top: 62%;
  width: 0;
  height: 0;
  transform-style: preserve-3d;
}

.c3__pt {
  position: absolute;
  left: 0;
  top: 0;
  width: 7px;
  height: 7px;
  margin: -3.5px 0 0 -3.5px;
  border-radius: 50%;
  background: #0a4fe8;
  will-change: transform;
}

.ld__badge {
  position: absolute;
  right: 8px;
  top: 8px;
  display: flex;
  align-items: baseline;
  gap: 4px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff7e6;
  font-weight: 700;
  font-size: 11px;
}

.ld__badgeNum {
  font-size: 13px;
  color: #ffd23f;
}

.ld__badgeUnit {
  font-weight: 700;
}

@media (max-width: 340px) {
  .ld {
    gap: 4px;
  }
  .ld__field {
    height: 124px;
  }
  .ld__badge {
    font-size: 10px;
    padding: 0 4px;
  }
  .ld__badgeNum {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ld.is-still .ld__field {
    cursor: default !important;
  }
  .ld.is-still .ld__badge {
    opacity: 0.92 !important;
  }
}

(function () {
'use strict';
var root = document.getElementById('ld');
var field = document.getElementById('field');
var pctEl = document.getElementById('pct');
var grid = document.getElementById('grid');

var GRID_COLS = 7;
var GRID_ROWS = 5;
var COL_GAP = 20;
var ROW_GAP = 24;
var HEIGHT_SCALE = 54;
var ROT_TURNS = 0.35;
var TILT = 58;

// 격자점마다 고정된 높이 가중치를 결정적으로 계산한다(무작위 없음) — 두 개의 sin/cos 물결을 겹친 값.
function weightOf(col, row) {
  return (Math.sin(col * 1.1 + row * 0.6) + Math.cos(row * 1.3 - col * 0.4) + 2) / 4;
}

var pts = [];
var base = [];
for (var row = 0; row < GRID_ROWS; row++) {
  for (var col = 0; col < GRID_COLS; col++) {
    var x = (col - (GRID_COLS - 1) / 2) * COL_GAP;
    var z = row * ROW_GAP;
    var w = weightOf(col, row);
    base.push([x, z, w]);
    var el = document.createElement('div');
    el.className = 'c3__pt';
    el.style.zIndex = String(row);
    grid.appendChild(el);
    pts.push(el);
  }
}

var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
var LOOP = 2;
var REDUCE_P = 0.7;
var t0 = 0, raf = 0, paused = false, lastP = 0;

function render(p) {
  lastP = p;
  var rotY = (p * 360 * ROT_TURNS) % 360;
  grid.style.transform = 'rotateX(' + TILT + 'deg) rotateZ(' + rotY + 'deg)';
  for (var i = 0; i < pts.length; i++) {
    var b = base[i];
    var rise = b[2] * p * HEIGHT_SCALE;
    pts[i].style.transform = 'translate3d(' + b[0] + 'px,' + (-rise) + 'px,' + b[1] + 'px)';
  }
  pctEl.textContent = Math.round(p * 100) + '%';
}

function frame(now) {
  if (!paused) { var t = (now - t0) / 1000; render((t % LOOP) / LOOP); }
  raf = requestAnimationFrame(frame);
}
function togglePause() {
  paused = !paused;
  root.classList.toggle('is-paused', paused);
  render(reduce ? REDUCE_P : lastP);
}
function restart() {
  t0 = performance.now();
  render(reduce ? REDUCE_P : 0);
}

field.addEventListener('click', function () { togglePause(); });
field.addEventListener('keydown', function (e) {
  if (e.key === ' ' || e.key === 'Enter') { e.preventDefault(); togglePause(); }
  else if (e.key === 'r' || e.key === 'R') { e.preventDefault(); restart(); }
});
window.addEventListener('resize', function () {
  if (paused || reduce) render(reduce ? REDUCE_P : lastP);
});

t0 = performance.now();
if (reduce) {
  root.classList.add('is-still');
  render(REDUCE_P);
} else {
  raf = requestAnimationFrame(frame);
}
})();

// TerrainGridRisePerspective — vanilla 판(run/399/demo/08-loader-3d-terrain-grid-rise-perspective/index.html) 의 React 포트.
// 격자점마다 고정된(무작위 없음) 높이 가중치를 결정적으로 계산해 진행률만큼 끌어올리고,
// 점마다 다른 Z 값을 CSS 원근 투영에 맡겨 가까운 점은 크게 먼 점은 작게 보이게 한다.
// 01~07 과 다른 축 — 고정 가중치 필드 값을 원근 투영과 결합한다.
import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./TerrainGridRisePerspective.module.scss";

export type TerrainGridRisePerspectiveProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };

const GRID_COLS = 7;
const GRID_ROWS = 5;
const COL_GAP = 20;
const ROW_GAP = 24;
const HEIGHT_SCALE = 54;
const ROT_TURNS = 0.35;
const TILT = 58;
const LOOP = 2;
const REDUCE_P = 0.7;
const FIELD_LABEL = "지형 격자 원근 진행 실험판";

function weightOf(col: number, row: number): number {
  return (Math.sin(col * 1.1 + row * 0.6) + Math.cos(row * 1.3 - col * 0.4) + 2) / 4;
}

const BASE: { x: number; z: number; w: number; row: number }[] = [];
for (let row = 0; row < GRID_ROWS; row++) {
  for (let col = 0; col < GRID_COLS; col++) {
    const x = (col - (GRID_COLS - 1) / 2) * COL_GAP;
    const z = row * ROW_GAP;
    BASE.push({ x, z, w: weightOf(col, row), row });
  }
}

export default function TerrainGridRisePerspective({
  duration = "2s",
  easing = "linear",
  color = "#0a4fe8",
}: TerrainGridRisePerspectiveProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const gridRef = useRef<HTMLDivElement | null>(null);
  const pctRef = useRef<HTMLSpanElement | null>(null);
  const ptsRef = useRef<(HTMLDivElement | null)[]>(new Array(BASE.length).fill(null)) as Box<(HTMLDivElement | null)[]>;
  const pausedRef = useRef(false) as Box<boolean>;
  const lastPRef = useRef(0) as Box<number>;
  const t0Ref = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function render(p: number): void {
    lastPRef.current = p;
    const rotY = (p * 360 * ROT_TURNS) % 360;
    const grid = gridRef.current;
    if (grid) grid.style.transform = "rotateX(" + TILT + "deg) rotateZ(" + rotY + "deg)";
    const pts = ptsRef.current;
    for (let i = 0; i < BASE.length; i++) {
      const el = pts[i];
      if (!el) continue;
      const b = BASE[i];
      const rise = b.w * p * HEIGHT_SCALE;
      el.style.transform = "translate3d(" + b.x + "px," + (-rise) + "px," + b.z + "px)";
    }
    if (pctRef.current) pctRef.current.textContent = Math.round(p * 100) + "%";
  }

  function togglePause(): void {
    pausedRef.current = !pausedRef.current;
    const root = rootRef.current;
    if (root) root.classList.toggle("is-paused", pausedRef.current);
    render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function restart(): void {
    t0Ref.current = performance.now();
    render(reduced() ? REDUCE_P : 0);
  }

  function onKey(e: KeyEvt): void {
    if (e.key === " " || e.key === "Enter") { e.preventDefault(); togglePause(); }
    else if (e.key === "r" || e.key === "R") { e.preventDefault(); restart(); }
  }

  function onClick(): void {
    togglePause();
  }

  function onResize(): void {
    if (pausedRef.current || reduced()) render(reduced() ? REDUCE_P : lastPRef.current);
  }

  function frame(now: number): void {
    if (!pausedRef.current) {
      const t = (now - t0Ref.current) / 1000;
      render((t % LOOP) / LOOP);
    }
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    t0Ref.current = performance.now();
    window.addEventListener("resize", onResize);
    if (reduced()) {
      const root = rootRef.current;
      if (root) root.classList.add("is-still");
      render(REDUCE_P);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.root} ref={rootRef} style={vars}>
        <p className={styles.hint}>클릭하거나 스페이스바를 누르면 멈추거나 다시 갑니다</p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onClick={onClick}
          onKeyDown={onKey}
        >
          <div className={styles.scene}>
            <div className={styles.grid} ref={gridRef}>
              {BASE.map((b, i) => (
                <div key={i} className={styles.pt} style={{ zIndex: b.row }} ref={(el: HTMLDivElement | null) => { ptsRef.current[i] = el; }} />
              ))}
            </div>
          </div>
          <b className={styles.badge} aria-hidden="true"><span className={styles.badgeNum} ref={pctRef}>0%</span><span className={styles.badgeUnit}>진행</span></b>
        </div>
      </div>
    </main>
  );
}