ModuleNotFoundError: No module named 'face_geometry'

[djipco]

When I try to run head_posture_rt.py, I get the following error:

Traceback (most recent call last):
  File ".\head_posture_rt.py", line 6, in <module>
    from face_geometry import get_metric_landmarks, PCF, canonical_metric_landmarks, procrustes_landmark_basis
ModuleNotFoundError: No module named 'face_geometry'

Is there anything else to install besides mediapipe?

P.S. Thanks for these examples, by the way!

[Rassibassi]

Hi,

the face_geometry module is within the same folder. So nothing else to install, other than numpy, opencv-python, mediapipe and pillow. It's strange that the import from webcamsource import WebcamSource seems to work when you call head_posture_rt.py.

Are you calling head_posture_rt.py from within the git reps root folder?

A quick hack to make things work, is just to comment the line with the face_geometry import, and just copy the functions and classes from that file into head_posture_rt.py.

Let me know if this problem persists, I'll write a little readme.

Best, Rasmus

[Rassibassi]

So, I added a README with install instructions for all the necessary packages, including an environment.yml, with all required version numbers. I'm using anaconda, so hope that's not a problem.

I tested the instructions and it works on my system, which is Ubuntu.

[djipco]

I wrongly assumed that face_geometry came from the mediapipe library. That's why I was confused. It's working fine now. Thanks for the clarification.

By the way, do you know what units are used by the vectors returned by cv2.solvePnP() ? I believe the rotation vector is expressed in radians but what about the translation vector? Are the values pixels or some other relative unit?

Thanks again.

[Rassibassi]

Not sure what the units are, but the unit of the Canonical Face Model from mediapipe is in cm. The vectors describe a translation/rotation from the Canonical Face Model to the 3D detected face (from model coordinate system to camera coordinate system).

(see here for a png version of the Canonical Face Model with indices of the points, same indices as held by the variable, points_idx, in the code)

The documentation of solvePnP says: rvec | Output rotation vector (see Rodrigues ) that, together with tvec , brings points from the model coordinate system to the camera coordinate system. tvec | Output translation vector.

The two vectors rotation_vector and translation_vector (rvec and tvec) are very similar to the pose_transform_mat obtained from the get_metric_landmarks() of my python mediapipe version. They actually should be the same, e.g. pose_transform_mat[:3,:3] and cv2.Rodrigues(rotation_vector)[0] should be the same, and also the last column of pose_transform_mat should be the same as tvec. However, somewhere a sign flip creeps in, see my comment here. This also means, one actually does not need the cv2.solvePnP() call, because all the information is already available in the pose_transform_mat, just in some kind of flipped coordinate system. Thus, one can just get the output of cv2.solvePnP() by looking at pose_transform_mat and applying some sign flips here and there. This again means that pose_transform_mat is in the same metric space as rotation_vector and translation_vector.

Sorry, I went on a tangent here, but (hence the above) my best guess is that rotation_vector is in radians and translation_vector is in cm.

If you'd like to read up on "3D reconstruction" of camera pictures see here, scroll a bit down to Detailed Description, where the camera calibration is explained. Or here