private void back_and_forth(double mirror) {
    CameraUniversalOmni model = createModel(mirror);

    UniOmniPtoS_F64 pixelToUnit = new UniOmniPtoS_F64();
    pixelToUnit.setModel(model);

    UniOmniStoP_F64 unitToPixel = new UniOmniStoP_F64();
    unitToPixel.setModel(model);

    List<Point2D_F64> listPixels = new ArrayList<>();
    listPixels.add(new Point2D_F64(320, 240));
    listPixels.add(new Point2D_F64(320, 200));
    listPixels.add(new Point2D_F64(320, 280));
    listPixels.add(new Point2D_F64(280, 240));
    listPixels.add(new Point2D_F64(360, 240));
    listPixels.add(new Point2D_F64(280, 240));
    listPixels.add(new Point2D_F64(240, 180));

    for (Point2D_F64 pixel : listPixels) {
      Point3D_F64 circle = new Point3D_F64(10, 10, 10);
      pixelToUnit.compute(pixel.x, pixel.y, circle); // directly forward on unit sphere

      // it should be on the unit circle
      assertEquals(1.0, circle.norm(), GrlConstants.DOUBLE_TEST_TOL);

      Point2D_F64 found = new Point2D_F64();
      unitToPixel.compute(circle.x, circle.y, circle.z, found);

      assertEquals(pixel.x, found.x, GrlConstants.DOUBLE_TEST_TOL_SQRT);
      assertEquals(pixel.y, found.y, GrlConstants.DOUBLE_TEST_TOL_SQRT);
    }
  }
  private void centerIsCenter(double mirror) {
    CameraUniversalOmni model = createModel(mirror);

    UniOmniPtoS_F64 alg = new UniOmniPtoS_F64();
    alg.setModel(model);

    Point3D_F64 found = new Point3D_F64(10, 10, 10);
    alg.compute(320, 240, found); // directly forward on unit sphere

    assertEquals(0, found.x, GrlConstants.DOUBLE_TEST_TOL);
    assertEquals(0, found.y, GrlConstants.DOUBLE_TEST_TOL);
    assertEquals(1, found.z, GrlConstants.DOUBLE_TEST_TOL);
  }