A model object MOB (tree) having a plurality of part objects (branches) POB1 and POB2 each of which has a projection shape is arranged in an object space. Each of the POB1 and POB2 has a projecting portion formed on a display surface on which an image is drawn. The POB1 and POB2 are rotated so that the display surfaces thereof are directed toward a virtual camera VC. A Z texture for setting bump shapes on the display surfaces by pixel unit or forming a virtual projection shape on each of the display surfaces is mapped on the POB1 and POB2. When the VC rotates about a Y-axis and an X-axis while being directed toward a column-shaped part object (trunk) COB, the POB1 and POB2 are rotated so that the display surfaces thereof are directed toward the VC.
Rotational image generation method, program, and information storage medium and virtual camera