Method for drawing object having rough model and detailed model

Detailed model data having numerous polygons and rough model data having fewer polygons are prepared for one object. A rectangular parallelepiped including the entire object is defined as a bounding box. A virtual three-dimensional space is perspective-transformed to divide an image-drawing field, which is an image drawing range, into a far image-drawing field and a near image-drawing field according to a distance from a viewpoint of virtual camera. When at least a part of the bounding box is included in the far image-drawing field, polygons of rough model data included in the far image-drawing field are drawn in a frame buffer. When at least a part of the bounding box is included in the near image-drawing field, polygons of detailed model data included in the near image-drawing field are drawn in a frame buffer.