Finding the ball is of essential importance for successful play. Although it seems to be an easy task, detecting the ball clearly demonstrates the difficulties of computer vision. Figure 3 shows some images of the ball. Its appearance varies greatly in size, shape, and color. Furthermore, it can be easily confused with robot markers. The detection of the ball can be summarized in three steps: (a) determine all clusters of the ball's color class and their sizes, (b) discard all clusters for which no transition to the floor can be found, and (c) choose the biggest cluster. Obstacles are detected as large clusters of the dark obstacle color. If clusters are close to each other, they are merged.
