First, at the point light source mode, a transformation processing for transforming a source video signal to obtain the shadow video signal V4 will be described with reference to FIGS. 7A and 7B. Note that, as with FIGS. 4A and 4B, FIG. 7A is a drawing of viewing the X-Y plane of the world coordinate system from the view point PZ set on the Z-axis of the world coordinate system, and FIG. 7B is a d