<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      padding: 10px;
      user-select: none;
    }

    /* Controls Header */
    .controls {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 10px;
    }
    .btn-group {
      display: flex;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 8px;
      gap: 2px;
    }
    .btn {
      border: none;
      background: transparent;
      padding: 6px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #64748b;
      border-radius: 6px;
      cursor: pointer;
      transition: background 0.15s ease, color 0.15s ease, box-shadow 0.15s ease;
    }
    .btn.active {
      background: #ffffff;
      color: #0284c7;
      box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }
    .toggle-btn {
      border: 1px solid #cbd5e1;
      background: #ffffff;
      padding: 6px 12px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      border-radius: 6px;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 6px;
      transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
    }
    .toggle-btn.active {
      background: #e0f2fe;
      border-color: #0ea5e9;
      color: #0284c7;
    }

    /* Grid Layout */
    .viewport-grid {
      display: grid;
      grid-template-columns: 1fr 1fr;
      gap: 10px;
      width: 100%;
    }
    .viewport-grid.focus-1 {
      grid-template-columns: 1fr;
    }
    .viewport-grid.focus-1 .card-2p {
      display: none;
    }
    .viewport-grid.focus-2 {
      grid-template-columns: 1fr;
    }
    .viewport-grid.focus-2 .card-1p {
      display: none;
    }

    /* Canvas Card */
    .perspective-card {
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px;
      display: flex;
      flex-direction: column;
      align-items: center;
      min-width: 0;
    }
    .card-header {
      width: 100%;
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 6px;
      font-size: 13px;
      font-weight: 700;
      color: #1e2945;
    }
    .badge {
      font-size: 10px;
      font-weight: 700;
      padding: 2px 6px;
      border-radius: 4px;
      text-transform: uppercase;
      letter-spacing: 0.3px;
    }
    .badge-1p { background: #e0f2fe; color: #0284c7; }
    .badge-2p { background: #fef3c7; color: #b45309; }

    /* SVG viewport */
    .svg-container {
      width: 100%;
      aspect-ratio: 16/11;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
      touch-action: none;
      display: block;
    }
    svg text {
      pointer-events: none;
      user-select: none;
    }
    svg circle {
      pointer-events: none;
    }

    /* Interactive Slider Toolbar */
    .slider-row {
      width: 100%;
      display: flex;
      align-items: center;
      gap: 8px;
      margin-top: 6px;
      font-size: 11px;
      color: #64748b;
      font-weight: 600;
    }
    .slider-row input[type="range"] {
      flex: 1;
      accent-color: #0ea5e9;
      cursor: pointer;
    }
    .slider-row.amber input[type="range"] {
      accent-color: #f59e0b;
    }

    /* Info Badge Callout */
    .callout {
      margin-top: 8px;
      font-size: 11px;
      font-weight: 600;
      line-height: 1.35;
      padding: 6px 8px;
      border-radius: 6px;
      width: 100%;
      text-align: center;
    }
    .callout-1p { background: #e0f2fe; color: #0369a1; }
    .callout-2p { background: #fef3c7; color: #92400e; }

    @media (max-width: 520px) {
      .viewport-grid {
        grid-template-columns: 1fr;
      }
    }
  </style>
</head>
<body>

  <div class="controls">
    <div class="btn-group">
      <button class="btn active" onclick="setMode('side')">Side-by-Side</button>
      <button class="btn" onclick="setMode('1p')">1-Point Focus</button>
      <button class="btn" onclick="setMode('2p')">2-Point Focus</button>
    </div>
    <button id="linesToggle" class="toggle-btn active" onclick="toggleLines()">
      <span>✦</span> Construction Lines
    </button>
  </div>

  <div id="viewGrid" class="viewport-grid">
    
    <div class="perspective-card card-1p">
      <div class="card-header">
        <span>1-Point Perspective</span>
        <span class="badge badge-1p">Head-on</span>
      </div>

      <div class="svg-container">
        <svg id="svg1" viewBox="0 0 300 200">
          <defs>
            <linearGradient id="grad1Front" x1="0" y1="0" x2="0" y2="1">
              <stop offset="0%" stop-color="#bae6fd" />
              <stop offset="100%" stop-color="#7dd3fc" />
            </linearGradient>
            <linearGradient id="grad1Top" x1="0" y1="0" x2="1" y2="1">
              <stop offset="0%" stop-color="#f0f9ff" />
              <stop offset="100%" stop-color="#e0f2fe" />
            </linearGradient>
            <linearGradient id="grad1Side" x1="0" y1="0" x2="1" y2="0">
              <stop offset="0%" stop-color="#38bdf8" />
              <stop offset="100%" stop-color="#0284c7" />
            </linearGradient>
          </defs>

          
          <line x1="0" y1="50" x2="300" y2="50" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="4 3" />
          <text x="8" y="42" fill="#64748b" font-size="9" font-weight="600">Horizon (Eye Level)</text>

          
          <g id="rays1" stroke="#0ea5e9" stroke-width="1" stroke-dasharray="3 3" opacity="0.85"></g>

          
          <polygon id="box1Side" fill="url(#grad1Side)" stroke="#0369a1" stroke-width="1.2" stroke-linejoin="round" />
          <polygon id="box1Top" fill="url(#grad1Top)" stroke="#0369a1" stroke-width="1.2" stroke-linejoin="round" />
          <rect id="box1Front" fill="url(#grad1Front)" stroke="#0284c7" stroke-width="1.8" />

          
          <circle id="vp1Dot" cx="150" cy="50" r="4" fill="#0284c7" />
          <text id="vp1Label" x="150" y="38" text-anchor="middle" fill="#0284c7" font-size="10" font-weight="700">VP 1</text>
        </svg>
      </div>

      <div class="slider-row">
        <span>Position X:</span>
        <input type="range" id="box1X" min="40" max="180" value="70" oninput="render1P()">
      </div>

      <div class="callout callout-1p">
        Front Face = True flat rectangle<br>Depth converges to 1 central VP
      </div>
    </div>

    
    <div class="perspective-card card-2p">
      <div class="card-header">
        <span>2-Point Perspective</span>
        <span class="badge badge-2p">Corner View</span>
      </div>

      <div class="svg-container">
        <svg id="svg2" viewBox="0 0 300 200">
          <defs>
            <linearGradient id="grad2Left" x1="0" y1="0" x2="1" y2="0">
              <stop offset="0%" stop-color="#fde68a" />
              <stop offset="100%" stop-color="#f59e0b" />
            </linearGradient>
            <linearGradient id="grad2Right" x1="0" y1="0" x2="1" y2="0">
              <stop offset="0%" stop-color="#38bdf8" />
              <stop offset="100%" stop-color="#0284c7" />
            </linearGradient>
            <linearGradient id="grad2Top" x1="0" y1="0" x2="1" y2="1">
              <stop offset="0%" stop-color="#ffffff" />
              <stop offset="100%" stop-color="#f1f5f9" />
            </linearGradient>
          </defs>

          
          <line x1="0" y1="50" x2="300" y2="50" stroke="#94a3b8" stroke-width="1.5" stroke-dasharray="4 3" />
          <text x="150" y="42" text-anchor="middle" fill="#64748b" font-size="9" font-weight="600">Horizon (Eye Level)</text>

          
          <g id="rays2Left" stroke="#f59e0b" stroke-width="1" stroke-dasharray="3 3" opacity="0.85"></g>
          <g id="rays2Right" stroke="#0ea5e9" stroke-width="1" stroke-dasharray="3 3" opacity="0.85"></g>

          
          <polygon id="box2Top" fill="url(#grad2Top)" stroke="#475569" stroke-width="1.2" stroke-linejoin="round" />
          <polygon id="box2Left" fill="url(#grad2Left)" stroke="#b45309" stroke-width="1.5" stroke-linejoin="round" />
          <polygon id="box2Right" fill="url(#grad2Right)" stroke="#0369a1" stroke-width="1.5" stroke-linejoin="round" />
          
          
          <line id="box2LeadingEdge" stroke="#1e2945" stroke-width="2.5" stroke-linecap="round" />

          
          <circle cx="20" cy="50" r="4" fill="#d97706" />
          <text x="20" y="38" text-anchor="middle" fill="#d97706" font-size="9" font-weight="700">VP Left</text>

          <circle cx="280" cy="50" r="4" fill="#0284c7" />
          <text x="280" y="38" text-anchor="middle" fill="#0284c7" font-size="9" font-weight="700">VP Right</text>
        </svg>
      </div>

      <div class="slider-row amber">
        <span>Corner X:</span>
        <input type="range" id="box2X" min="100" max="200" value="150" oninput="render2P()">
      </div>

      <div class="callout callout-2p">
        Leading Edge = True vertical<br>Left/Right faces recede to 2 VPs
      </div>
    </div>
  </div>

  <script>
    let showLines = true;

    function setMode(mode) {
      const grid = document.getElementById('viewGrid');
      const btns = document.querySelectorAll('.btn-group .btn');
      btns.forEach(b => b.classList.remove('active'));

      grid.classList.remove('focus-1', 'focus-2');

      if (mode === 'side') {
        btns[0].classList.add('active');
      } else if (mode === '1p') {
        grid.classList.add('focus-1');
        btns[1].classList.add('active');
      } else if (mode === '2p') {
        grid.classList.add('focus-2');
        btns[2].classList.add('active');
      }
    }

    function toggleLines() {
      showLines = !showLines;
      const btn = document.getElementById('linesToggle');
      if (showLines) {
        btn.classList.add('active');
      } else {
        btn.classList.remove('active');
      }
      document.getElementById('rays1').style.display = showLines ? 'block' : 'none';
      document.getElementById('rays2Left').style.display = showLines ? 'block' : 'none';
      document.getElementById('rays2Right').style.display = showLines ? 'block' : 'none';
    }

    // 1-Point Perspective Rendering
    function render1P() {
      const vp = { x: 150, y: 50 };
      const bx = parseFloat(document.getElementById('box1X').value);
      const by = 120;
      const bw = 65;
      const bh = 50;
      const depthT = 0.45; // interpolation factor toward VP

      // Front Face Corners
      const fTL = { x: bx, y: by };
      const fTR = { x: bx + bw, y: by };
      const fBR = { x: bx + bw, y: by + bh };
      const fBL = { x: bx, y: by + bh };

      // Back Face Corners (projected towards VP)
      const bTL = { x: fTL.x + (vp.x - fTL.x) * depthT, y: fTL.y + (vp.y - fTL.y) * depthT };
      const bTR = { x: fTR.x + (vp.x - fTR.x) * depthT, y: fTR.y + (vp.y - fTR.y) * depthT };
      const bBR = { x: fBR.x + (vp.x - fBR.x) * depthT, y: fBR.y + (vp.y - fBR.y) * depthT };
      const bBL = { x: fBL.x + (vp.x - fBL.x) * depthT, y: fBL.y + (vp.y - fBL.y) * depthT };

      // Update Front Face
      const front = document.getElementById('box1Front');
      front.setAttribute('x', bx);
      front.setAttribute('y', by);
      front.setAttribute('width', bw);
      front.setAttribute('height', bh);

      // Top Polygon
      const topPoly = document.getElementById('box1Top');
      topPoly.setAttribute('points', `${fTL.x},${fTL.y} ${bTL.x},${bTL.y} ${bTR.x},${bTR.y} ${fTR.x},${fTR.y}`);

      // Side Polygon (depends on if box is left or right of VP)
      const sidePoly = document.getElementById('box1Side');
      if (bx + bw < vp.x) {
        // Right side visible
        sidePoly.setAttribute('points', `${fTR.x},${fTR.y} ${bTR.x},${bTR.y} ${bBR.x},${bBR.y} ${fBR.x},${fBR.y}`);
        sidePoly.style.display = 'block';
      } else if (bx > vp.x) {
        // Left side visible
        sidePoly.setAttribute('points', `${fTL.x},${fTL.y} ${bTL.x},${bTL.y} ${bBL.x},${bBL.y} ${fBL.x},${fBL.y}`);
        sidePoly.style.display = 'block';
      } else {
        sidePoly.style.display = 'none';
      }

      // Construction Rays
      const rays = document.getElementById('rays1');
      rays.innerHTML = `
        <line x1="${fTL.x}" y1="${fTL.y}" x2="${vp.x}" y2="${vp.y}" />
        <line x1="${fTR.x}" y1="${fTR.y}" x2="${vp.x}" y2="${vp.y}" />
        <line x1="${fBR.x}" y1="${fBR.y}" x2="${vp.x}" y2="${vp.y}" />
        <line x1="${fBL.x}" y1="${fBL.y}" x2="${vp.x}" y2="${vp.y}" />
      `;
    }

    // 2-Point Perspective Rendering
    function render2P() {
      const vpL = { x: 20, y: 50 };
      const vpR = { x: 280, y: 50 };
      const cx = parseFloat(document.getElementById('box2X').value);
      const topY = 110;
      const botY = 170;
      const depthL = 0.45;
      const depthR = 0.45;

      // Leading Corner Edge
      const cTop = { x: cx, y: topY };
      const cBot = { x: cx, y: botY };

      // Left Back Edge
      const lTop = { x: cTop.x + (vpL.x - cTop.x) * depthL, y: cTop.y + (vpL.y - cTop.y) * depthL };
      const lBot = { x: cBot.x + (vpL.x - cBot.x) * depthL, y: cBot.y + (vpL.y - cBot.y) * depthL };

      // Right Back Edge
      const rTop = { x: cTop.x + (vpR.x - cTop.x) * depthR, y: cTop.y + (vpR.y - cTop.y) * depthR };
      const rBot = { x: cBot.x + (vpR.x - cBot.x) * depthR, y: cBot.y + (vpR.y - cBot.y) * depthR };

      // Far Top Corner (Intersection of lTop -> vpR and rTop -> vpL)
      const x1 = lTop.x, y1 = lTop.y, x2 = vpR.x, y2 = vpR.y;
      const x3 = rTop.x, y3 = rTop.y, x4 = vpL.x, y4 = vpL.y;

      const denom = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
      const farTopX = ((x1 * y2 - y1 * x2) * (x3 - x4) - (x1 - x2) * (x3 * y4 - y3 * x4)) / denom;
      const farTopY = ((x1 * y2 - y1 * x2) * (y3 - y4) - (y1 - y2) * (x3 * y4 - y3 * x4)) / denom;

      // Update Left Face
      document.getElementById('box2Left').setAttribute('points', 
        `${cTop.x},${cTop.y} ${lTop.x},${lTop.y} ${lBot.x},${lBot.y} ${cBot.x},${cBot.y}`);

      // Update Right Face
      document.getElementById('box2Right').setAttribute('points', 
        `${cTop.x},${cTop.y} ${rTop.x},${rTop.y} ${rBot.x},${rBot.y} ${cBot.x},${cBot.y}`);

      // Update Top Face
      document.getElementById('box2Top').setAttribute('points', 
        `${cTop.x},${cTop.y} ${lTop.x},${lTop.y} ${farTopX},${farTopY} ${rTop.x},${rTop.y}`);

      // Update Leading Edge
      const leadingEdge = document.getElementById('box2LeadingEdge');
      leadingEdge.setAttribute('x1', cTop.x);
      leadingEdge.setAttribute('y1', cTop.y);
      leadingEdge.setAttribute('x2', cBot.x);
      leadingEdge.setAttribute('y2', cBot.y);

      // Rays Left
      document.getElementById('rays2Left').innerHTML = `
        <line x1="${cTop.x}" y1="${cTop.y}" x2="${vpL.x}" y2="${vpL.y}" />
        <line x1="${cBot.x}" y1="${cBot.y}" x2="${vpL.x}" y2="${vpL.y}" />
        <line x1="${rTop.x}" y1="${rTop.y}" x2="${vpL.x}" y2="${vpL.y}" />
      `;

      // Rays Right
      document.getElementById('rays2Right').innerHTML = `
        <line x1="${cTop.x}" y1="${cTop.y}" x2="${vpR.x}" y2="${vpR.y}" />
        <line x1="${cBot.x}" y1="${cBot.y}" x2="${vpR.x}" y2="${vpR.y}" />
        <line x1="${lTop.x}" y1="${lTop.y}" x2="${vpR.x}" y2="${vpR.y}" />
      `;
    }

    // Initial render
    render1P();
    render2P();
  </script>
</body>
</html>

Understanding Parallel vs Central Perspective Projections

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; font-family: system-ui, -apple-system, sans-serif; }
    body {
      background: #f8f9fa;
      color: #1e2945;
      padding: 10px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 8px;
    }
    @media (min-width: 580px) {
      .grid {
        grid-template-columns: repeat(4, 1fr);
      }
    }
    .proj-card {
      background: #ffffff;
      border: 1.5px solid #e2e8f0;
      border-radius: 10px;
      padding: 8px;
      display: flex;
      flex-direction: column;
      align-items: center;
      cursor: pointer;
      user-select: none;
      transition: box-shadow 0.2s ease, border-color 0.2s ease;
    }
    .proj-card.active {
      border-color: #22b7ff;
      box-shadow: 0 0 0 2px #22b7ff;
      background: #f0f9ff;
    }
    .title {
      font-size: 13px;
      font-weight: 700;
      text-align: center;
      margin-bottom: 4px;
      color: #1e2945;
    }
    .svg-wrap {
      width: 100%;
      height: 86px;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    svg {
      width: 100%;
      height: 100%;
      overflow: visible;
    }
    .badges {
      width: 100%;
      display: flex;
      flex-direction: column;
      gap: 3px;
      margin-top: 6px;
    }
    .badge {
      display: flex;
      justify-content: space-between;
      align-items: center;
      background: #f1f5f9;
      padding: 2px 6px;
      border-radius: 4px;
      font-size: 11px;
      font-weight: 600;
    }
    .badge-label {
      color: #64748b;
      font-size: 10px;
    }
    .badge-val {
      font-weight: 700;
    }
    .val-yes { color: #0284c7; }
    .val-no { color: #d97706; }
    .val-partial { color: #475569; }

    .callout {
      background: #ffffff;
      border: 1.5px solid #22b7ff;
      border-radius: 8px;
      padding: 8px 12px;
      display: flex;
      align-items: center;
      gap: 8px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      box-shadow: 0 2px 6px rgba(34, 183, 255, 0.12);
    }
    .callout-icon {
      font-size: 16px;
      color: #22b7ff;
      flex-shrink: 0;
    }
  </style>
</head>
<body>

  <div class="grid">
    
    <div class="proj-card" onclick="selectCard(0)">
      <div class="title">Orthographic</div>
      <div class="svg-wrap">
        <svg viewBox="0 0 140 85">
          
          <rect x="20" y="8" width="45" height="22" fill="#bae6fd" stroke="#0284c7" stroke-width="1.5"/>
          <text x="42.5" y="22" font-size="8" font-weight="700" fill="#0369a1" text-anchor="middle">TOP</text>
          
          
          <rect x="20" y="40" width="45" height="36" fill="#e0f2fe" stroke="#0284c7" stroke-width="1.5"/>
          <text x="42.5" y="62" font-size="8" font-weight="700" fill="#0369a1" text-anchor="middle">FRONT</text>
          
          
          <rect x="76" y="40" width="28" height="36" fill="#7dd3fc" stroke="#0284c7" stroke-width="1.5"/>
          <text x="90" y="62" font-size="8" font-weight="700" fill="#0369a1" text-anchor="middle">SIDE</text>
          
          
          <line x1="65" y1="40" x2="76" y2="40" stroke="#94a3b8" stroke-dasharray="2 2" stroke-width="1"/>
          <line x1="65" y1="76" x2="76" y2="76" stroke="#94a3b8" stroke-dasharray="2 2" stroke-width="1"/>
          <line x1="20" y1="30" x2="20" y2="40" stroke="#94a3b8" stroke-dasharray="2 2" stroke-width="1"/>
          <line x1="65" y1="30" x2="65" y2="40" stroke="#94a3b8" stroke-dasharray="2 2" stroke-width="1"/>
        </svg>
      </div>
      <div class="badges">
        <div class="badge"><span class="badge-label">∥ Lines:</span><span class="badge-val val-yes">✓ Parallel</span></div>
        <div class="badge"><span class="badge-label">Scale:</span><span class="badge-val val-yes">1:1 True</span></div>
        <div class="badge"><span class="badge-label">Use:</span><span class="badge-val val-partial">Plans</span></div>
      </div>
    </div>

    
    <div class="proj-card" onclick="selectCard(1)">
      <div class="title">Oblique</div>
      <div class="svg-wrap">
        <svg viewBox="0 0 140 85">
          
          <polygon points="25,38 52,16 102,16 75,38" fill="#bae6fd" stroke="#0284c7" stroke-width="1.5"/>
          
          <polygon points="75,38 102,16 102,54 75,76" fill="#7dd3fc" stroke="#0284c7" stroke-width="1.5"/>
          
          <rect x="25" y="38" width="50" height="38" fill="#e0f2fe" stroke="#0284c7" stroke-width="1.5"/>
          
          <line x1="75" y1="38" x2="92" y2="38" stroke="#94a3b8" stroke-dasharray="2 2" stroke-width="1"/>
          <path d="M 88,38 A 12,12 0 0,0 83,31" fill="none" stroke="#f59e0b" stroke-width="1.2"/>
          <text x="96" y="34" font-size="7" font-weight="700" fill="#d97706">45°</text>
        </svg>
      </div>
      <div class="badges">
        <div class="badge"><span class="badge-label">∥ Lines:</span><span class="badge-val val-yes">✓ Parallel</span></div>
        <div class="badge"><span class="badge-label">Scale:</span><span class="badge-val val-partial">Front True</span></div>
        <div class="badge"><span class="badge-label">Use:</span><span class="badge-val val-partial">Diagrams</span></div>
      </div>
    </div>

    
    <div class="proj-card active" onclick="selectCard(2)">
      <div class="title">1-Pt Perspective</div>
      <div class="svg-wrap">
        <svg viewBox="0 0 140 85">
          
          <line x1="5" y1="20" x2="135" y2="20" stroke="#cbd5e1" stroke-width="1"/>
          <circle cx="115" cy="20" r="2.5" fill="#ef4444"/>
          <text x="115" y="14" font-size="7" font-weight="700" fill="#ef4444" text-anchor="middle">VP</text>

          
          <line x1="20" y1="42" x2="115" y2="20" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="1"/>
          <line x1="68" y1="42" x2="115" y2="20" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="1"/>
          <line x1="68" y1="78" x2="115" y2="20" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="1"/>

          
          <polygon points="20,42 42,32 80,32 68,42" fill="#bae6fd" stroke="#0284c7" stroke-width="1.5"/>
          
          <polygon points="68,42 80,32 80,62 68,78" fill="#7dd3fc" stroke="#0284c7" stroke-width="1.5"/>
          
          <rect x="20" y="42" width="48" height="36" fill="#e0f2fe" stroke="#0284c7" stroke-width="1.5"/>
        </svg>
      </div>
      <div class="badges">
        <div class="badge"><span class="badge-label">∥ Lines:</span><span class="badge-val val-no">✗ Converge</span></div>
        <div class="badge"><span class="badge-label">Scale:</span><span class="badge-val val-partial">Front True</span></div>
        <div class="badge"><span class="badge-label">Use:</span><span class="badge-val val-partial">Tracks/Halls</span></div>
      </div>
    </div>

    
    <div class="proj-card" onclick="selectCard(3)">
      <div class="title">2-Pt Perspective</div>
      <div class="svg-wrap">
        <svg viewBox="0 0 140 85">
          
          <line x1="5" y1="18" x2="135" y2="18" stroke="#cbd5e1" stroke-width="1"/>
          <circle cx="10" cy="18" r="2.5" fill="#ef4444"/>
          <circle cx="130" cy="18" r="2.5" fill="#ef4444"/>
          <text x="12" y="12" font-size="7" font-weight="700" fill="#ef4444">VP1</text>
          <text x="128" y="12" font-size="7" font-weight="700" fill="#ef4444" text-anchor="end">VP2</text>

          
          <line x1="70" y1="36" x2="10" y2="18" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="0.8"/>
          <line x1="70" y1="78" x2="10" y2="18" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="0.8"/>
          <line x1="70" y1="36" x2="130" y2="18" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="0.8"/>
          <line x1="70" y1="78" x2="130" y2="18" stroke="#fca5a5" stroke-dasharray="2 2" stroke-width="0.8"/>

          
          <polygon points="70,36 38,28 72,23 104,29" fill="#bae6fd" stroke="#0284c7" stroke-width="1.5"/>
          
          <polygon points="70,36 38,28 38,62 70,78" fill="#e0f2fe" stroke="#0284c7" stroke-width="1.5"/>
          
          <polygon points="70,36 104,29 104,64 70,78" fill="#7dd3fc" stroke="#0284c7" stroke-width="1.5"/>
          
          <line x1="70" y1="36" x2="70" y2="78" stroke="#0369a1" stroke-width="2"/>
        </svg>
      </div>
      <div class="badges">
        <div class="badge"><span class="badge-label">∥ Lines:</span><span class="badge-val val-no">✗ Converge</span></div>
        <div class="badge"><span class="badge-label">Scale:</span><span class="badge-val val-no">Distorted</span></div>
        <div class="badge"><span class="badge-label">Use:</span><span class="badge-val val-partial">Buildings</span></div>
      </div>
    </div>
  </div>

  
  <div class="callout" id="calloutBox">
    <div class="callout-icon">✦</div>
    <div id="calloutText">1-Point: Receding depth lines meet at 1 single horizon point.</div>
  </div>

  <script>
    const explanations = [
      "Orthographic: Flat 90° projections preserve true measurements with zero perspective.",
      "Oblique: True front dimensions, while depth lines extend parallel at a fixed angle.",
      "1-Point: Receding depth lines meet at 1 single horizon point.",
      "2-Point: Angled corner view; edges converge to 2 separate horizon points."
    ];

    function selectCard(index) {
      const cards = document.querySelectorAll('.proj-card');
      cards.forEach((c, i) => {
        if (i === index) c.classList.add('active');
        else c.classList.remove('active');
      });
      document.getElementById('calloutText').textContent = explanations[index];
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      background: #ffffff;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 12px 14px 8px;
      user-select: none;
      min-height: 100%;
    }
    .controls {
      display: flex;
      gap: 10px;
      margin-bottom: 6px;
      z-index: 10;
    }
    .btn {
      background: #f8f9fa;
      border: 2px solid #cbd5e1;
      color: #1e2945;
      padding: 7px 20px;
      border-radius: 20px;
      font-size: 15px;
      font-weight: 700;
      cursor: pointer;
      transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
    }
    .btn:hover {
      background: #e2e8f0;
      border-color: #94a3b8;
    }
    .btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.35);
    }
    .diagram-container {
      width: 100%;
      max-width: 580px;
      display: flex;
      justify-content: center;
    }
    .diagram-svg {
      width: 100%;
      height: auto;
      max-height: 380px;
      display: block;
    }
    .ray {
      stroke: #0284c7;
      stroke-width: 2.2;
      stroke-dasharray: 6 4;
      transition: all 0.4s ease;
    }
    .projected-shape {
      transition: all 0.4s ease;
    }
    .focal-element {
      transition: opacity 0.35s ease;
    }
  </style>
</head>
<body>

  <div class="controls">
    <button id="btnParallel" class="btn active" onclick="setMode('parallel')" aria-label="Show Parallel Projection">Parallel</button>
    <button id="btnCentral" class="btn" onclick="setMode('central')" aria-label="Show Central Projection">Central</button>
  </div>

  <div class="diagram-container">
    <svg class="diagram-svg" viewBox="0 0 580 300" aria-label="3D Projection Comparison Diagram">
      <defs>
        
        <linearGradient id="screenGrad" x1="0%" y1="0%" x2="100%" y2="100%">
          <stop offset="0%" stop-color="#f8fafc" />
          <stop offset="100%" stop-color="#cbd5e1" />
        </linearGradient>
        
        <linearGradient id="cubeTop" x1="0%" y1="0%" x2="100%" y2="100%">
          <stop offset="0%" stop-color="#bae6fd" />
          <stop offset="100%" stop-color="#7dd3fc" />
        </linearGradient>
        <linearGradient id="cubeFront" x1="0%" y1="0%" x2="0%" y2="100%">
          <stop offset="0%" stop-color="#38bdf8" />
          <stop offset="100%" stop-color="#0284c7" />
        </linearGradient>
        <linearGradient id="cubeSide" x1="0%" y1="0%" x2="100%" y2="0%">
          <stop offset="0%" stop-color="#0284c7" />
          <stop offset="100%" stop-color="#0369a1" />
        </linearGradient>
      </defs>

      
      <g id="screenGroup">
        <polygon points="475,30 515,55 515,285 475,260" fill="url(#screenGrad)" stroke="#64748b" stroke-width="2" />
        <text x="495" y="24" text-anchor="middle" font-size="15" font-weight="700" fill="#1e2945">Screen</text>
      </g>

      
      <g id="raysGroup">
        <line id="ray1" class="ray" x1="50" y1="120" x2="485" y2="120" />
        <line id="ray2" class="ray" x1="50" y1="180" x2="485" y2="180" />
        <line id="ray3" class="ray" x1="50" y1="90"  x2="500" y2="90" />
        <line id="ray4" class="ray" x1="50" y1="150" x2="500" y2="150" />
      </g>

      
      <g id="cubeGroup">
        
        <polygon points="200,120 235,90 295,90 260,120" fill="url(#cubeTop)" stroke="#0369a1" stroke-width="1.5" />
        
        <polygon points="260,120 295,90 295,150 260,180" fill="url(#cubeSide)" stroke="#0369a1" stroke-width="1.5" />
        
        <polygon points="200,120 260,120 260,180 200,180" fill="url(#cubeFront)" stroke="#0369a1" stroke-width="1.5" opacity="0.95" />
        <text x="247" y="208" text-anchor="middle" font-size="15" font-weight="700" fill="#1e2945">3D Object</text>
      </g>

      
      <g id="projectionGroup">
        <polygon id="projTop" class="projected-shape" points="480,120 495,90 510,90 495,120" fill="#38bdf8" opacity="0.5" />
        <polygon id="projSide" class="projected-shape" points="495,120 510,90 510,150 495,180" fill="#0284c7" opacity="0.6" />
        <polygon id="projFront" class="projected-shape" points="480,120 495,120 495,180 480,180" fill="#0284c7" opacity="0.85" stroke="#0369a1" stroke-width="1.5" />
      </g>

      
      
      <g id="parallelSource" class="focal-element" opacity="1">
        <line x1="50" y1="70" x2="50" y2="200" stroke="#0284c7" stroke-width="4.5" stroke-linecap="round" />
        <circle cx="50" cy="90" r="5" fill="#0284c7" />
        <circle cx="50" cy="120" r="5" fill="#0284c7" />
        <circle cx="50" cy="150" r="5" fill="#0284c7" />
        <circle cx="50" cy="180" r="5" fill="#0284c7" />
        <text x="50" y="226" text-anchor="middle" font-size="15" font-weight="700" fill="#0369a1">Parallel</text>
      </g>

      
      <g id="centralSource" class="focal-element" opacity="0" pointer-events="none">
        <circle cx="50" cy="150" r="9" fill="#0284c7" />
        <circle cx="50" cy="150" r="3.5" fill="#ffffff" />
        
        <text x="50" y="125" text-anchor="middle" font-size="22">👁️</text>
        <text x="50" y="180" text-anchor="middle" font-size="15" font-weight="700" fill="#0369a1">Focal Point</text>
      </g>
    </svg>
  </div>

  <script>
    function setMode(mode) {
      const btnP = document.getElementById('btnParallel');
      const btnC = document.getElementById('btnCentral');
      const srcP = document.getElementById('parallelSource');
      const srcC = document.getElementById('centralSource');
      
      const r1 = document.getElementById('ray1');
      const r2 = document.getElementById('ray2');
      const r3 = document.getElementById('ray3');
      const r4 = document.getElementById('ray4');

      const pFront = document.getElementById('projFront');
      const pTop = document.getElementById('projTop');
      const pSide = document.getElementById('projSide');

      if (mode === 'parallel') {
        btnP.classList.add('active');
        btnC.classList.remove('active');
        
        srcP.style.opacity = '1';
        srcC.style.opacity = '0';

        // Parallel horizontal rays
        r1.setAttribute('x1', '50'); r1.setAttribute('y1', '120'); r1.setAttribute('x2', '480'); r1.setAttribute('y2', '120');
        r2.setAttribute('x1', '50'); r2.setAttribute('y1', '180'); r2.setAttribute('x2', '480'); r2.setAttribute('y2', '180');
        r3.setAttribute('x1', '50'); r3.setAttribute('y1', '90');  r3.setAttribute('x2', '495'); r3.setAttribute('y2', '90');
        r4.setAttribute('x1', '50'); r4.setAttribute('y1', '150'); r4.setAttribute('x2', '495'); r4.setAttribute('y2', '150');

        // Preserved 1:1 projection
        pTop.setAttribute('points', '480,120 495,90 510,90 495,120');
        pSide.setAttribute('points', '495,120 510,90 510,150 495,180');
        pFront.setAttribute('points', '480,120 495,120 495,180 480,180');
      } else {
        btnC.classList.add('active');
        btnP.classList.remove('active');

        srcP.style.opacity = '0';
        srcC.style.opacity = '1';

        // Radiating rays from focal point (50, 150)
        r1.setAttribute('x1', '50'); r1.setAttribute('y1', '150'); r1.setAttribute('x2', '480'); r1.setAttribute('y2', '64');
        r2.setAttribute('x1', '50'); r2.setAttribute('y1', '150'); r2.setAttribute('x2', '480'); r2.setAttribute('y2', '236');
        r3.setAttribute('x1', '50'); r3.setAttribute('y1', '150'); r3.setAttribute('x2', '495'); r3.setAttribute('y2', '46');
        r4.setAttribute('x1', '50'); r4.setAttribute('y1', '150'); r4.setAttribute('x2', '495'); r4.setAttribute('y2', '150');

        // Magnified perspective projection
        pTop.setAttribute('points', '480,64 495,46 510,68 495,98');
        pSide.setAttribute('points', '495,98 510,68 510,184 495,206');
        pFront.setAttribute('points', '480,64 495,98 495,206 480,236');
      }
    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      min-height: 100%;
      background: transparent;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      padding: 8px;
    }
    .grid {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
      gap: 16px;
      width: 100%;
      max-width: 720px;
      margin: 0 auto;
    }
    .panel {
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 4px;
    }
    .title-badge {
      font-size: 13px;
      font-weight: 700;
      letter-spacing: 0.03em;
      color: #0f172a;
      margin-bottom: 8px;
      text-transform: uppercase;
      text-align: center;
    }
    svg {
      width: 100%;
      height: auto;
      max-height: 270px;
      display: block;
    }
    .shape-front {
      fill: #e0f2fe;
      stroke: #0ea5e9;
      stroke-width: 2;
      stroke-linejoin: round;
    }
    .shape-side {
      fill: #bae6fd;
      stroke: #0284c7;
      stroke-width: 2;
      stroke-linejoin: round;
    }
    .shape-top {
      fill: #f1f5f9;
      stroke: #64748b;
      stroke-width: 2;
      stroke-linejoin: round;
    }
    .dim-line {
      stroke: #94a3b8;
      stroke-width: 1.2;
      stroke-dasharray: 3 3;
    }
    .angle-arc {
      fill: none;
      stroke: #e11d48;
      stroke-width: 1.5;
    }
    .label {
      font-size: 11px;
      fill: #1e2945;
      font-weight: 700;
      text-anchor: middle;
      font-family: inherit;
    }
    .label-muted {
      font-size: 10px;
      fill: #64748b;
      font-weight: 600;
      text-anchor: middle;
      font-family: inherit;
    }
    .highlight-badge {
      font-size: 10px;
      font-weight: 700;
      fill: #0284c7;
      text-anchor: middle;
    }
  </style>
</head>
<body>
  <div class="grid">
    
    <div class="panel">
      <div class="title-badge">Orthographic Multi-View</div>
      <svg viewBox="0 0 280 240" aria-label="Orthographic Multi-View Diagram">
        
        <g transform="translate(45, 22)">
          
          <text x="35" y="-7" class="label-muted">TOP VIEW</text>
          
          <rect x="0" y="0" width="70" height="20" class="shape-top" />
          <rect x="0" y="20" width="70" height="20" class="shape-top" />
          
          <line x1="0" y1="20" x2="70" y2="20" stroke="#64748b" stroke-width="1.5" />
        </g>

        
        <line x1="45" y1="62" x2="45" y2="95" class="dim-line" />
        <line x1="115" y1="62" x2="115" y2="95" class="dim-line" />
        <line x1="115" y1="125" x2="155" y2="125" class="dim-line" />
        <line x1="115" y1="175" x2="155" y2="175" class="dim-line" />

        
        <g transform="translate(45, 95)">
          
          <rect x="0" y="30" width="70" height="50" class="shape-front" />
          
          <polygon points="0,30 35,0 70,30" class="shape-front" />
          <text x="35" y="58" class="label">FRONT</text>

          
          <path d="M 0,72 L 8,72 L 8,80" fill="none" stroke="#0ea5e9" stroke-width="1.2" />
        </g>

        
        <g transform="translate(155, 95)">
          <rect x="0" y="30" width="60" height="50" class="shape-side" />
          <rect x="0" y="5" width="60" height="25" class="shape-side" opacity="0.85" />
          <text x="30" y="58" class="label">RIGHT</text>

          
          <path d="M 52,80 L 52,72 L 60,72" fill="none" stroke="#0284c7" stroke-width="1.2" />
        </g>

        
        <rect x="25" y="195" width="105" height="22" rx="4" fill="#e0f2fe" stroke="#bae6fd" stroke-width="1" />
        <text x="77" y="210" class="highlight-badge">True Shape & 90°</text>

        <rect x="145" y="195" width="85" height="22" rx="4" fill="#f1f5f9" stroke="#cbd5e1" stroke-width="1" />
        <text x="187" y="210" class="label-muted">2D Flat Views</text>
      </svg>
    </div>

    
    <div class="panel">
      <div class="title-badge">Oblique Projection</div>
      <svg viewBox="0 0 280 240" aria-label="Oblique Projection Diagram">
        
        <line x1="125" y1="180" x2="195" y2="180" stroke="#94a3b8" stroke-width="1" stroke-dasharray="3 3" />
        <line x1="125" y1="180" x2="175" y2="130" stroke="#e11d48" stroke-width="1.5" />
        <path d="M 150,180 A 25 25 0 0 0 143,162" class="angle-arc" />
        <text x="160" y="172" fill="#e11d48" font-size="11px" font-weight="700">45°</text>

        
        
        <polygon points="125,180 175,130 175,80 125,130" class="shape-side" />
        
        
        <polygon points="90,100 140,50 175,80 125,130" class="shape-side" opacity="0.85" />
        
        
        <polygon points="55,130 105,80 140,50 90,100" class="shape-top" />

        
        <polygon points="55,130 90,100 125,130" class="shape-front" />
        <rect x="55" y="130" width="70" height="50" class="shape-front" />
        <text x="90" y="158" class="label">FRONT</text>

        
        <path d="M 55,172 L 63,172 L 63,180" fill="none" stroke="#0ea5e9" stroke-width="1.2" />

        
        <rect x="25" y="195" width="110" height="22" rx="4" fill="#e0f2fe" stroke="#bae6fd" stroke-width="1" />
        <text x="80" y="210" class="highlight-badge">True Front Shape</text>

        <rect x="145" y="195" width="110" height="22" rx="4" fill="#ffe4e6" stroke="#fecdd3" stroke-width="1" />
        <text x="200" y="210" fill="#e11d48" font-size="10px" font-weight="700" text-anchor="middle">45° Parallel Depth</text>
      </svg>
    </div>
  </div>
</body>
</html>

OGM.9.TRN.4

Aligned learning resources

Related diagrams