Function buildParentFaceMap

js/main.js:3696–3816

* Build a mapping from each subdivided face to its nearest original face * using a grid-accelerated nearest-centroid lookup, with face normal * tiebreaking to prevent boundary faces from being mapped to the wrong * original face (e.g. a subdivided face on a cube edge mapped to the * adjacent fac

(subdivGeo)

      // Count triangles in this shell
      let count = 0;
      for (let tt = 0; tt < triCount; tt++) if (shellIds[tt] === s) count++;
      const outPos = new Float32Array(count * 9);
      const outNrm = srcNrm ? new Float32Array(count * 9) : null;
      let dst = 0;
      for (let tt = 0; tt < triCount; tt++) {
        if (shellIds[tt] !== s) continue;
        const src = tt * 9;
        outPos.set(srcPos.subarray(src, src + 9), dst);
        if (outNrm) outNrm.set(srcNrm.subarray(src, src + 9), dst);
        dst += 9;
      }
      const geo = new THREE.BufferGeometry();
      geo.setAttribute('position', new THREE.BufferAttribute(outPos, 3));
      if (outNrm) geo.setAttribute('normal', new THREE.BufferAttribute(outNrm, 3));
      addDiagFaces(geo, SHELL_COLORS[s % SHELL_COLORS.length], 0.55);
    }
  } else if (kind === 'intersects' && lastAdvancedDiag && lastAdvancedDiag.intersectFaces) {
    const geo = buildExclusionOverlayGeo(currentGeometry, lastAdvancedDiag.intersectFaces);
    addDiagFaces(geo, 0xff0000, 0.7, true);
  } else if (kind === 'bodyIntersects' && lastAdvancedDiag && lastAdvancedDiag.bodyIntersectFaces) {
    const geo = buildExclusionOverlayGeo(currentGeometry, lastAdvancedDiag.bodyIntersectFaces);
    addDiagFaces(geo, 0xf59e0b, 0.7, true);
  } else if (kind === 'overlaps' && lastAdvancedDiag && lastAdvancedDiag.overlapFaces) {
    const geo = buildExclusionOverlayGeo(currentGeometry, lastAdvancedDiag.overlapFaces);
    addDiagFaces(geo, 0xf59e0b, 0.7);
  }
}

/**
 * Build a single issue line element with a "Show" toggle button.
 * @param {string} text  – the issue description
 * @param {string} kind  – highlight kind key
 * @returns {HTMLElement}
 */
function makeDiagLine(text, kind) {
  const row = document.createElement('div');
  row.style.cssText = 'display:flex;justify-content:space-between;align-items:baseline;gap:8px';
  const span = document.createElement('span');
  span.textContent = '\u26a0 ' + text;
  const btn = document.createElement('button');
  btn.className = 'diag-show-btn';
  btn.dataset.kind = kind;
  btn.textContent = activeDiagHighlight === kind ? t('diag.hide') : t('diag.show');
  btn.addEventListener('click', () => toggleDiagHighlight(kind));
  row.appendChild(span);
  row.appendChild(btn);
  return row;
}

function renderFastDiag(diag) {
  meshDiagFast.innerHTML = '';

  const defects = diag.openEdges > 0 || diag.nonManifoldEdges > 0;
  if (!defects) meshDiagFast.textContent = t('diag.meshOk');
  if (diag.openEdges > 0)
    meshDiagFast.appendChild(makeDiagLine(t('diag.openEdges', { n: diag.openEdges }), 'openEdges'));
  if (diag.nonManifoldEdges > 0)
    meshDiagFast.appendChild(makeDiagLine(t('diag.nonManifoldEdges', { n: diag.nonManifoldEdges }), 'nonManifold'));