I am trying to project points on an image after estimating its pose as shown in this OpenCV tutorial, but for any textured "base image" instead of a chessboard image.
To match the base image with a frame from my webcam, I'm using ORB and FLANN and it is working perfectly. The 2D border around the image is correctly rendered with cv2.findHomography and cv2.perspectiveTransform(border_points, homography_matrix) to map the points and cv2.polylines to draw them.
Now I should be able to draw 3D axes on the image's surface using the homography matrix, but I'm stuck not knowing how I would do it nor finding how to do it anywhere. What am I missing here?
# target_pts and webcam_pts are arrays of 2D points generated by ORB
homography_matrix, _ = cv2.findHomography(target_pts, webcam_pts, cv2.RANSAC, 5.0)
_, rvecs, tvecs, _ = cv2.decomposeHomographyMat(homography_matrix, calibration_matrix)
axis = np.float32([[3,0,0], [0,3,0], [0,0,-3]]).reshape(-1,3)
# TODO: cv2.Rodrigues() for rvecs ?
axis_points, _ = cv2.projectPoints(axis, rvecs[0], tvecs[0], calibration_matrix, calibration_coefficients)
# Draw axis_points on image
# ...