docs: private void mapMouseToPlane(Simple1DOFCamera camera, Point point2d, double[] vec) {
      // Far plane
      camera.unproject(point2d.x, point2d.y, -100., far);
      // Near plane
      camera.unproject(point2d.x, point2d.y, 1., near);
      // Delta vector: far -= near.
      VMath.minusEquals(far, near);
      // Intersection with z=0 plane:
      // far.z - a * near.z = 0 -> a = far.z / near.z
      if (near[2] < 0 || near[2] > 0) {
        double a = far[2] / near[2];
        vec[0] = far[0] - a * near[0];
        vec[1] = far[1] - a * near[1];
        vec[2] = 0;
      }
    }