Monday, March 07, 2005
How it works
ARToolKit uses computer vision techniques to calculate the real camera viewpoint relative to a real world marker. There are several steps as shown in images below. First the live video image (left) is turned into a binary (black or white) image based on a lighting threshold value (center). This image is then searched for square regions. ARToolKit finds all the squares in the binary image, many of which are not the tracking markers. For each square, the pattern inside the square is captured and matched again some pre-trained pattern templates. If there is a match, then ARToolKit has found one of the AR tracking markers. ARToolKit then uses the known square size and pattern orientation to calculate the position of the real video camera relative to the physical marker. A 3x4 matrix is filled in with the video camera real world coordinates relative to the card. This matrix is then used to set the position of the virtual camera coordinates. Since the virtual and real camera coordinates are the same, the computer graphics that are drawn precisely overlay the real marker (right). The OpenGL API is used for setting the virtual camera coordinates and drawing the virtual images.
# posted by Paul Mason @ 6:00 PM 
