It is intended to solve the problem that, when an operator performs an
operation using two-dimensional input means while seeing a picture frame
seen from a viewpoint of the operator, an input operation is difficult to
perform when the direction of the line of sight of the operator is
unstable, since a designated direction greatly deviates in a world
coordinate system. For that purpose, viewpoint information is detected,
and an instruction of the operator for operating a position of a pointer
image is input. A designated direction in a pointer coordinate system is
obtained in accordance with the operator's instruction, and the pointer
image is generated based on the designated direction. The pointer
coordinate system is changed from the detected viewpoint information in
accordance with a specific instruction of the operator.