Abstract: First, a process of moving an object such as a train is executed. Then, the influential ranges of virtual winds that are correlated with the object in advance are moved with a movement of the object. Based on the moved influential ranges of the virtual winds, it is judged whether each particle object is influenced by the virtual winds. The position of each particle object for which a judgment has been made that it is influenced by a virtual wind is determined in accordance with the direction of the influential virtual wind. Particle objects that have contacted the object are deleted. The object and the position-determined particle objects are drawn in a frame buffer. An image drawn in the frame buffer is displayed on a display screen.