These elements may be used on their own, or in concert with miniatures to map out combats, and exploration or to introduce other visual media into the game without resorting to printing or drawing these items.; Webcam enabled computer-assisted wargames use computer vision to process firing with images of the camera. In the case of an external USB camera, it is placed behind the firing unit selected (third person shooter) in the direction of the target. When a tablet is used the rear webcam is selected. Precise positioning of the webcam behind the shooting unit is not required : it is sufficient both the shooting unit and the target unit are displayed on the captured image for the shot to be valid. This makes the usage of a tablet very practical for these games. Target detection algorithms (improved magic wand contour, polygon simplification, convex hull algorithms, polygon degree of convexity) allow to analyze the characteristics of the target and to estimate the distance to the target. Damage is computed by taking into the account distance (in distance units) between the firing unit and the target, the type of gun (anti-tank value) of the firing unit and the thickness of the armor of the target (defend value).