Function transformCameraPose

src/utils/sim3dTransforms.ts:175–200

(
  newFromOld: Sim3d,
  qvec: [number, number, number, number],
  tvec: [number, number, number]
)

 * @returns Transformed qvec and tvec
 */
export function transformCameraPose(
  newFromOld: Sim3d,
  qvec: [number, number, number, number],
  tvec: [number, number, number]
): { qvec: [number, number, number, number]; tvec: [number, number, number] } {
  // Step 1: Create Sim3d from camera pose with scale=1
  // Note: COLMAP uses [w, x, y, z], Three.js uses (x, y, z, w)
  const camFromWorld: Sim3d = {
    scale: 1,
    rotation: new THREE.Quaternion(qvec[1], qvec[2], qvec[3], qvec[0]),
    translation: new THREE.Vector3(tvec[0], tvec[1], tvec[2]),
  };

  // Step 2: cam_from_new_world = cam_from_old_world * Inverse(new_from_old_world)
  const oldFromNew = inverseSim3d(newFromOld);
  const camFromNew = composeSim3d(camFromWorld, oldFromNew);

  // Step 3: Scale translation by original scale (CRITICAL - from COLMAP source)
  const scaledT = camFromNew.translation.clone().multiplyScalar(newFromOld.scale);

  // Step 4: Convert back to COLMAP qvec format [w, x, y, z]
  return {
    qvec: [camFromNew.rotation.w, camFromNew.rotation.x, camFromNew.rotation.y, camFromNew.rotation.z],
    tvec: [scaledT.x, scaledT.y, scaledT.z],
  };
}

// ============================================================================
// Reconstruction-level Transforms