In applications of augmented reality or virtual reality, fiducials are often manually applied to objects in a scene so that the objects can be recognized in images of the scene → Fiduciary_marker

• Feature Matching + Homography to find Objects at OpenCV Python
• opencv python fiducial demo Python code using numpy & cv2.
• Tutorial: OpenCV haartraining (Rapid Object Detection With A Cascade of Boosted Classifiers Based on Haar-like Features)

ARTag “Magic Lens” and “Magic Mirror” systems use arrays of the square ARTag markers added to objects or the environment allowing a computer vision algorithm to calculate the camera “pose” in real time, allowing the CG (computer graphics) virtual camera to be aligned.