Filed on July 21, 2004.

1. A three-dimensional image generating apparatus for generating a three-dimensional image according to an operator's operation input, comprising: an operation input detecting means for detecting the operator's operation input; an object data storing means for storing object data for rendering objects forming a three-dimensional image; a displaying means for displaying an image projected onto a projection screen within a virtual three-dimensional space; a virtual three-dimensional space generating means for generating said virtual three-dimensional space based on the operation input detected by said operation input detecting means and the object data stored in said object data storing means; a viewpoint controlling means for controlling a viewpoint within the virtual three-dimensional space generated by said virtual three-dimensional space generating means; a display image generating means for generating said image of said virtual three-dimensional space seen from the viewpoint controlled by said viewpoint controlling means, which is projected onto said projection screen; a depth value storing means for storing a depth value of each pixel of the image generated by said display image generating means; an object arrangement position storing means for storing at least an arrangement position of a specific object in said virtual three-dimensional space; a determination point setting means for setting a predetermined number of determination points in a predetermined area containing the arrangement position of said specific object in said image; a determining means for determining whether or not a first depth value of the predetermined number of determination points set by said determination point setting means is smaller than a second depth value of said specific object; and a degree-of-hiding calculating means for calculating a degree of hiding of said specific object according to the number of said determination points where it is determined by said determining means that said first depth value is smaller than said second depth value.

2. A three-dimensional image generating apparatus according to claim 1, wherein said determination point setting means sets said determination points in an area adjacent to and embracing said specific object projected onto said projection screen.

3. A three-dimensional image generating apparatus according to claim 1, wherein in case where said specific object in said virtual three-dimensional space is projected onto said projection screen, said determination point setting means sets said determination points on the circumference of a circle adjacent to and embracing the specific object projected onto the projection screen.