Function inverseSim3d

src/utils/sim3dTransforms.ts:118–133

(bFromA: Sim3d)

 * - translation_inv = (rotation_inv * translation) / -scale
 */
export function inverseSim3d(bFromA: Sim3d): Sim3d {
  const scaleInv = 1 / bFromA.scale;
  const rotationInv = bFromA.rotation.clone().invert();

  // t_inv = (R_inv * t) / -scale = R_inv * t * (-1/scale)
  const translationInv = bFromA.translation
    .clone()
    .applyQuaternion(rotationInv)
    .multiplyScalar(-scaleInv);

  return {
    scale: scaleInv,
    rotation: rotationInv,
    translation: translationInv,
  };
}

/**
 * Compose two Sim3d transforms: c_from_a = c_from_b * b_from_a