3D points projection using multiple camera

I am using Python with OpenCV 3.4.

I have a system composed of 2 cameras that I want to use to track an object and get its trajectory, then its speed.

I am currently able to calibrate intrinsically and extrinsically each of my cameras. I can track my object through the video and get the 2d coordinates in my video plan.

My problem now is that I would like to project my points from my both 2D plan into 3D points. I've tried functions as triangulatePoints but it seems it's not working in a proper way. Here is my actual function to get 3d coords. It returns some coordinates that seems a little bit off compared to the actual coordinates

def get_3d_coord(left_two_d_coords, right_two_d_coords):

    pt1 = left_two_d_coords.reshape((len(left_two_d_coords), 1, 2))
    pt2 = right_two_d_coords.reshape((len(right_two_d_coords), 1, 2))

    extrinsic_left_camera_matrix, left_distortion_coeffs, extrinsic_left_rotation_vector, \
        extrinsic_left_translation_vector = trajectory_utils.get_extrinsic_parameters(
            1)

    extrinsic_right_camera_matrix, right_distortion_coeffs, extrinsic_right_rotation_vector, \
        extrinsic_right_translation_vector = trajectory_utils.get_extrinsic_parameters(
            2)

    #returns arrays of the same size
    (pt1, pt2) = correspondingPoints(pt1, pt2)



    projection1 = computeProjMat(extrinsic_left_camera_matrix,
                                    extrinsic_left_rotation_vector, extrinsic_left_translation_vector)
    projection2 = computeProjMat(extrinsic_right_camera_matrix,
                                    extrinsic_right_rotation_vector, extrinsic_right_translation_vector)

    out = cv2.triangulatePoints(projection1, projection2, pt1, pt2)

    oc = []
    for idx, elem in enumerate(out[0]):
        oc.append((out[0][idx], out[1][idx], out[2][idx], out[3][idx]))

    oc = np.array(oc, dtype=np.float32)

    point3D = []

    for idx, elem in enumerate(oc):
        W = out[3][idx]
        obj = [None] * 4
        obj[0] = out[0][idx] / W
        obj[1] = out[1][idx] / W
        obj[2] = out[2][idx] / W
        obj[3] = 1

        pt3d = [obj[0], obj[1], obj[2]]
        point3D.append(pt3d)

    return point3D

from 3D points projection using multiple camera