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)

• reacTIVision a toolkit for tangible multi-touch surfaces.
  • reacTIVision is an open source, cross-platform computer vision framework for the fast and robust tracking of fiducial markers attached onto physical objects, as well as for multi-touch finger tracking. It was mainly designed as a toolkit for the rapid development of table-based tangible user interfaces (TUI) and multi-touch interactive surfaces. {{ http://raw.githubusercontent.com/mattvenn/fiducial/master/artags/artag_rotate.jpg?200}} [[http://www.artag.net/|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.