Virtual image generation apparatus and method

Abstract

A virtual image generation apparatus comprising shape data memory for storing shape data pertaining to obstacles and the like, position data specifier for specifying position data for the subjects, overlap determiner for determining, on the basis of shape data and position data, whether or not physical objects located between a visual point and a subject should overlap and be visible from the visual point, and image generator for generating virtual images wherein physical objects are processed by prescribed show-through processing (mesh processing, translucent processing, or the like) when it is determined that an overlapping state exists. Accurate overlap determinations can be made using a vector that extends from the visual point towards an object and a vector that extends from an obstacle towards the object, and mesh processing or other show-through processing used to produce a suitable display of the subject obscured by a physical object.

1. A virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator-controlled object moving relative to virtual terrain objects, the operator-controlled object and the terrain objects being defined within a three-dimensional virtual space, the virtual generation apparatus comprising:
 shape data memory which stores shape data defining shapes of the terrain objects present in the virtual space;    position specification means which specifies position of the operator-controlled object with respect to the terrain objects;    overlap determination means which determines, on the basis of the shape data and the position data, whether or not a terrain object is located between the viewpoint and the operator-controlled object; and    image generation means which generates image data for displaying on a monitor screen the operator-controlled object and the terrain objects viewed from the viewpoint, wherein a terrain object is processed so as to be displayed as a show-through image generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern through which the operator-controlled object can be viewed in the event that the overlap determination means determines that the operator-controlled object is located behind the terrain object when viewed from the viewpoint, and wherein the terrain object is processed so as to be displayed as a non-show-through image in the event that both the operator-controlled object and the terrain object are viewed without a prescribed overlapping state from the viewpoint.    
     
     
       2. A virtual image generation apparatus as defined in  claim 1 , wherein the overlap determination means compares a displacement from a prescribed ground point for a first reference point specified for the operator-controlled object with a displacement from a ground point for a second reference point specified for the terrain object, and in the event that the displacement for the first reference point is smaller than the displacement for the second reference point, decides that the operator-controlled object is located behind the terrain object when viewed from the viewpoint. 
     
     
       3. A virtual image generation apparatus as defined in  claim 1 , wherein said terrain objects include one or more of an explosion, an enemy robot, an obstacle background, a building and topographical features. 
     
     
       4. A virtual image generation apparatus as defined in  claim 1 , wherein said show-through image for the terrain object overlapping the operator-controlled object is rendered translucent. 
     
     
       5. A virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator-controlled object moving relative to virtual terrain objects, the operator-controlled object and the terrain objects being defined within a three-dimensional virtual space, comprising:
 shape data memory which stores shape data defining shapes of the terrain objects present in the virtual space;    position specification means which specifies position of the operator-controlled object with respect to the terrain objects;    overlap determination means which determines, on the basis of the shape data and the position data, whether or not a terrain object is located between the viewpoint and the operator-controlled object; and    image generation means which generates image data for displaying on the monitor the operator-controlled object and the terrain objects viewed from the viewpoint, wherein a terrain object is processed so as to be displayed as a show-through image generated by displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern through which the operator-controlled object can be viewed in the event that the overlap determination means determines that the operator-controlled object is located behind the terrain object when viewed from the viewpoint;    wherein the overlap determination means computes a first vector which extends in a direction in which the operator-controlled object is observed from the view-point and a second vector which extends from the terrain object towards the operator-controlled object, computes the angle formed by the obtained first vector and second vector, and, in the event that this angle falls within a prescribed relationship with regard to a prescribed reference angle, determines that the operator controlled object is located behind the terrain object when viewed from the viewpoint.    
     
     
       6. A virtual image generation apparatus as defined in  claim 5 , wherein the overlap determination means makes a determination that the operator-controlled object is located behind the object when viewed from the viewpoint in the event that the angle falls within the prescribed relationship with regard to the reference angle as well as in the event that a displacement of the operator-controlled object is smaller than a displacement of the terrain object, wherein the displacement of the operator-controlled object is the displacement from a prescribed ground point for a first reference point specified for the operator-controlled object and the displacement of the terrain object is the displacement from a ground point for a second reference point specified for the terrain object. 
     
     
       7. A virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator-controlled object moving relative to virtual terrain objects, the operator-controlled object and the terrain objects being defined within a three-dimensional virtual space, the virtual generation apparatus comprising:
 shape data memory which stores shape data defining shapes of the terrain objects present in the virtual space;    position specification means which specifies position of the operator-controlled object with respect to the terrain objects;    overlap determination means which determines, on the basis of the shape data and the position data, whether or not a terrain object is located between the viewpoint and the operator-controlled object; and    image generation means which generates image data for displaying on a monitor screen the operator-controlled object and the terrain objects viewed from the viewpoint, wherein a terrain object is processed so as to be displayed as a show-through image generated by displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a mesh form pattern with an alternating sequence of pixels for displaying the terrain object and pixels for displaying the operator-controlled object and through which the operator-controlled object can be viewed in the event that the overlap determination means determines that the operator-controlled object is located behind the terrain object when viewed from the viewpoint, and wherein the terrain object is processed so as to be displayed as a non-show-through image in the event that both the operator-controlled object and the terrain object are viewed without a prescribed overlapping state from the viewpoint.    
     
     
       8. A virtual image generation method which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator-controlled object moving relative to virtual terrain objects, the operator-controlled object and the terrain objects being defined within a three-dimensional virtual space, the method comprising the steps of:
 storing shape data defining shapes of the terrain objects;    computing the position of the operator-controlled object with respect to the terrain objects;    determining, on the basis of the shape data and the position data, for the operator-controlled object, whether a terrain object is located between the viewpoint and the operator-controlled object in an overlapping state when viewed from the viewpoint; and    generating / data for displaying on the monitor the operator-controlled object and the terrain objects viewed from the viewpoint, in which a terrain object in an overlapping state is processed so as to be displayed as a show-through image generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern through which the operator controlled object can be viewed in the event that the terrain object is located between the viewpoint and the operator-controlled object in an overlapping state when viewed from the viewpoint, and in which a terrain object disposed in a state other than the overlapping state is displayed as a non-show-through image.    
     
     
       9. A virtual image generation method as defined in  claim 8 , wherein said terrain objects include one or more of an explosion, an enemy robot, an obstacle background, a building and topographical features. 
     
     
       10. An information storing medium for use with a virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator-controlled object moving relative to virtual terrain objects, the operator-controled object and the terrain objects being defined within a three-dimensional virtual space, the information storing medium storing a program which executes the steps of:
 supplying shape data defining shapes of objects to be displayed;    computing position of the operator-controled object with respect to the terrain objects;    determining, on the basis of the shape data relating to the terrain objects present in the virtual space and the position data, for the operator-controled object, whether any of the terrain objects is located between the viewpoint and the operator-controlled object in an overlapping state when viewed from the viewpoint; and    generating image data for displaying on the monitor the operator-controlled object and the objects viewed from the viewpoint, in which any terrain object in an overlapping state is processed so as to be displayed as a show-through image generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controled object in a prescribed pattern through which the operator controlled object can be viewed in the event that the terrain object is located between the viewpoint and the operator-controlled object in an overlapping state when viewed from the viewpoint, and in which any of the terrain objects disposed in a state other than the overlapping state is displayed as a non-show-through image.    
     
     
       11. An information storing method as defined in  claim 10 , wherein said terrain objects include one or more of an explosion, an enemy robot, an obstacle background, a building and topographical features. 
     
     
       12. A game device which generates images observed from a viewpoint to be displayed on a monitor, the images including a player-controlled object moving relative to image terrain objects, the player-controlled object and the terrain objects being defined within a three-dimensional virtual space, the game device comprising:
 an input means with which a game player operates a computer game;    shape data memory which stores shape data defining shapes of the terrain objects present in the virtual space;    a position data specifier which specifies a current position for the player-controlled object with respect to the terrain objects;    overlap determination means which determines, on the basis of the shape data and the position data, whether or not a terrain object is located between the viewpoint and the player-controlled object; and    an image generator which generates image data for displaying on the monitor screen the player-controlled object and the terrain objects viewed from the viewpoint wherein a terrain object is processed so as to be displayed as a show-through image generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern through which the player-controlled object is viewed in the event that the overlap determiner determines that the player-controlled object is located behind the terrain object in an overlapping state when viewed from the viewpoint, and wherein a terrain object is displayed without such show-through image effect in the event that the player-controlled object and the terrain object are disposed in a state other than the overlapping state.    
     
     
       13. A game device as defined by  claim 12 , wherein the overlap determiner:
 compares a displacement from a ground point for a first reference point for the player-controlled object with a displacement from the ground point for a second reference point for the terrain object; and    determines whether an overlap state, in which the player-controlled object is located behind the terrain object when viewed from the viewpoint, exists in accordance with whether the displacement for the first reference point is smaller than the displacement for the second reference point.    
     
     
       14. A game device as defined in  claim 12 , wherein said terrain objects include one or more of an explosion, an enemy robot, an obstacle background, a building and topographical features defined in the three-dimensional virtual space. 
     
     
       15. A game device as defined in  claim 12 , wherein said show-through image is rendered translucent. 
     
     
       16. A game device which generates images observed from a viewpoint to be displayed on a monitor, the images including a player-controlled object moving relative to virtual terrain objects, the player-controlled object and the terrain objects being defined within a three-dimensional virtual space, the game device comprising:
 an input means with which a game player operates a computer game;  
 shape data memory which stores shape data defining shapes of the terrain objects present in the virtual space;  
 a position data specifier which specifies a current position for the player-controlled object with respect to the terrain objects;  
 overlap determination meansa processor which determines, on the basis of the shape data and the position data, whether a terrain object is located between the viewpoint and the player-controlled object; and  
 an image generator which generates image data for displaying on the monitor screen the player-controlled object and the terrain objects viewed from the viewpoint wherein a terrain object is processed so as to be rendered as a show-through image through which the player-controlled object is viewed in the event that the overlap determiner  processor determines that the player-controlled object is intervened by the terrain object in an overlapping state when viewed from the viewpoint,  
 wherein said overlap determiner  processor computes a first vector that extends in a direction in which said player-controlled object is observed from said viewpoint, and a second vector that extends from said terrain object towards said player-controlled object, computes an angle formed by said first vector and said second vector, and determines whether or not said player controlled object is intervened by the terrain object when viewed from the viewpoint in an overlap state in accordance with whether said angle falls within a prescribed relationship with a reference angle.  
 
     
     
       17. A game device as defined by  claim 16 , wherein the overlap determiner  processor:
 compares a displacement from a ground point for a first reference point for the player-controlled object with a displacement from the ground point for a second reference point for the terrain object; and  
 determines whether an overlap state, in which the player-controlled object is intervened by the terrain object when viewed from the viewpoint, exists in accordance with whether an angle falls within a prescribed relationship with a reference angle and the displacement for the first reference point is smaller than the displacement for the second reference point.  
 
     
     
       18. A computer system comprising a graphic image processor wherein various objects are defined in a three-dimensional virtual space and programs are executed in response to an operator's instruction so that an operator-controlled object moves against a terrain composed of terrain objects defined in the three-dimensional virtual space and images of the operator controlled object and the terrain objects viewed from at least one viewpoint are generated for displaying on a monitor, the computer system comprising:
 an input means which is manually controlled by an operator, the image of the operator-controlled object moves in response to the operator's control with the input means;    shape data memory stored with shape data for objects; and    processing means for generating images of the operator-controlled object and the terrain objects for displaying on the monitor,    wherein the processing means determines positions of the operator-controlled object with respect to the terrain objects and, in the event that a terrain object is located between the viewpoint and the operator-controlled object in the three-dimensional virtual space when viewed from the viewpoint, generates a portion of the terrain object overlapping with the operator-controlled object with a show-through image effect generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern.    
     
     
       19. The computer system of  claim 18 , wherein said show-through image effect is rendered by processing said overlapping portion with a translucent effect. 
     
     
       20. A computer system defining various objects in a three-dimensional virtual space and executing programs that respond to an operator's instruction so that a operator-controlled object moves against a terrain composed of terrain objects defined in the three-dimensional virtual space and images of such objects viewed from a viewpoint are generated for displaying on a monitor, the computer system comprising:
 an input means which is manually controlled by an operator, the image of the operator-controlled object moving in response to the operator's control with the input means; and    processing means for generating images of the operator-controlled object and the terrain objects for displaying on a monitor,    wherein the processing means determines positions of the operator-controlled object with respect to the terrain objects and, in the event that a terrain object is located between the viewpoint and the operator-controlled object in the three-dimensional virtual space when viewed from the viewpoint, generates a portion of the terrain object overlapping with the operator-controlled object with a show-through image effect generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern.    
     
     
       21. A method of generating images on a computer system, the computer system defining objects in a three-dimensional virtual space, the objects including an operator-controlled object and a terrain composed of terrain objects, and wherein the computer system generates images of the objects viewed from a viewpoint for displaying on a monitor, the method comprising the steps of:
 receiving signals from an input means controlled by an operator;    processing the signals so that operator-controlled object moves relative to their terrain objects in response to the signals;    determining the positions of the operator controlled object with respect to the terrain;    generating images of the operator-controlled object and the terrain objects viewed from the viewpoint for displaying on the monitor,    wherein, in the event that a terrain object is located between the viewpoint and the operator-controlled object in the three dimensional virtual space when viewed from the viewpoint, a portion of the terrain object overlapping with the operator controlled object is generated with a show-through effect generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern.    
     
     
       22. An information storing medium for use with a game provided by a computer system, wherein the game comprises objects in a three-dimensional virtual space, the objects including an operator-controlled object and a terrain composed of terrain objects, and wherein the computer system generates images of the objects viewed from a viewpoint for displaying on a monitor, the medium storing a program which executes the steps of:
 receiving signals from an input means controlled by an operator;    processing the signals so that operator-controlled object moves relative to their terrain objects in response to the signals;    determining positions of the operator controlled object with respect to the terrain objects; and    generating images of the operator-controlled object and the terrain objects viewed from the viewpoint for displaying on the monitor,    wherein, in the event that a terrain object is located between the viewpoint and the operator-controlled object in the three dimensional virtual space when viewed from the viewpoint, a portion of the terrain object overlapping with the operator controlled object is generated with a show-through effect generated by alternately displaying pixels indicative of the terrain object and pixels indicative of the operator-controlled object in a prescribed pattern.    
     
     
       23. A virtual image generation apparatus for a game, wherein the game comprises an operator-controlled object moving relative to terrain objects within a three-dimensional virtual space, the virtual image generation apparatus comprising:
 shape data memory which stores data defining shapes of a plurality of terrain objects within the three-dimensional virtual space;    position specification means which specifies a position of the operator-controlled object within the virtual space;    overlap determination means which determines whether one of the terrain objects is located between a viewpoint and the operator-controlled object;    first image generation means which generates image data for the operator-controlled object and the plurality of terrain objects as viewed from the viewpoint; and    second image generation means which generates image data for the operator-controlled object and the terrain objects comprising alternately generating pixels indicative of at least one of the terrain objects and indicative of the operator-controlled object in a prescribed pattern if the overlap determination means determines that the operator-controlled object is located behind the at least one terrain object when viewed from the viewpoint.    
     
     
       24. A virtual image generation method for a game, wherein the game comprises an operator-controlled object moving relative to terrain objects within a three-dimensional virtual space, the virtual image generation method comprising the steps of:
 storing data defining shapes of a plurality of terrain objects within the three-dimensional virtual space;    computing the position of the operator-controlled object within the virtual space;    determining whether one of the terrain objects is located between a viewpoint and the operator-controlled object; and    generating image data for the operator-controlled object and the plurality of terrain objects as viewed from the viewpoint;    wherein generating image data for the operator-controlled object and at least one of the terrain objects comprises alternately generating pixels indicative of the at least one terrain object and indicative of the operator-controlled object in a prescribed pattern if the operator-controlled object is located behind the at least one terrain object when viewed from the viewpoint.    
     
     
       25. An information storing medium storing a program for a game, wherein the game comprises an operator-controlled object moving relative to terrain objects within a three-dimensional virtual space, the program which executes the steps of:
 storing data defining shapes of a plurality of terrain objects within the three-dimensional virtual space;    computing the position of the operator-controlled object within the virtual space;    determining whether one of the terrain objects is located between a viewpoint and the operator-controlled object; and    generating image data for the operator-controlled object and the terrain objects as viewed from the viewpoint;    wherein generating image data for the operator-controlled object and at least one of the terrain objects comprises alternately generating pixels indicative of the at least one terrain object and indicative of the operator-controlled object in a prescribed pattern if the operator-controlled object is located behind the at least one terrain object when viewed from the viewpoint.    
     
     
       26. A computer system configured as a game device, wherein the game device comprises an operator-controlled object moving relative to terrain objects within a three-dimensional virtual space, the computer system comprising:
 an input means for operating the operator-controlled object;    first generating means for generating image data of the operator-controlled object and a plurality of terrain objects from a plurality of viewpoints,    processing means for determining the position of the operator-controlled object with respect to the plurality of terrain objects as viewed from a viewpoint; and    second generating means for generating image data for the operator-controlled object and the terrain objects comprising alternately generating pixels indicative of at least one of the terrain objects and indicative of the operator-controlled object in a prescribed pattern if the operator-controlled object is located behind the at least one terrain object when viewed from the viewpoint.    
     
     
       27. A game device, wherein the game device comprises a player-controlled object moving relative to terrain objects within a three-dimensional virtual space, the game device comprising:
 a controller for operating the player-controlled object;    a shape data memory which stores data defining shapes of a plurality of terrain objects present in the three-dimensional virtual space;    a position data specifier which specifies a current position for the player-controlled object within the virtual space;    an overlap determination processor which determines whether one of the terrain objects is located between a viewpoint and the player-controlled object; and    an image generator which generates image data for the player-controlled object and the terrain objects as viewed from the viewpoint and image data for the player-controlled object and the terrain object comprising alternately generating pixels indicative of at least one of the terrain objects and indicative of the player-controlled object in a prescribed pattern if the overlap determination processor determines that the player-controlled object is located behind the at least one terrain object when viewed from the viewpoint.    
     
     
       28. A virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator- controlled object moving relative to virtual physical objects, the operator - controlled object and the vector physical objects being defined within a three - dimensional virtual space, the virtual generation apparatus comprising:      shape data memory which stores shape data defining shapes of the virtual physical objects present in the virtual space;        position data specification means for specifying position data of the operator - controlled object with respect to the virtual physical objects;        a processor that determines, on the basis of the shape data and the position data, whether or not one of the virtual physical objects is located between the viewpoint and the operator - controlled object; and        image generation means for generating image data for displaying on the monitor the operator - controlled object and the virtual physical objects viewed from the viewpoint, wherein one of the virtual physical objects is processed so as to be displayed as a show - through image generated in a prescribed pattern through which the operator - controlled object can be viewed in the event that the processor determines that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object,        wherein the virtual physical object is processed so as to be displayed as a non - show - through image in the event that both the operator - controlled object and the virtual physical object are viewed without a prescribed overlapping state from the viewpoint, and        the processor computes a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector that extends from the virtual physical object towards the operator - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       29. The virtual image generation apparatus of  claim 28 , wherein the shape data memory further stores a plurality of flags indicating whether the processor should determine whether the virtual physical objects are located between the viewpoint and the operator- controlled object, and      wherein when one of the plurality of flags indicates that the processor should not determine whether the virtual physical objects are located between the viewpoint and the operator - controlled object, the processor does not make the determination.     
     
     
       30. The virtual image generation apparatus of  claim 28 , further comprising:
   a status flag register that stores a status flag indicating whether or not a height of the virtual physical object is such that the operator - controlled object is substantially obscured by the virtual physical object.     
     
     
       31. A virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator- controlled object moving relative to virtual physical objects, the operator - controlled object and the virtual physical objects being defined within a three - dimensional virtual space, comprising:      shape data memory which stores shape data defining shapes of the virtual physical objects present in the virtual space;        position data specification means for specifying position data of the operator - controlled object with respect to the virtual physical objects;        a processor that determines, on the basis of the shape data and the position data, whether or not one of the virtual physical objects is located between the viewpoint and the operator - controlled object; and        image generation means for generating image data for displaying on the monitor the operator - controlled object and the virtual physical objects viewed from the viewpoint, wherein one of the virtual physical objects is processed so as to be displayed as a show - through image generated in a prescribed pattern through which the operator - controlled object can be viewed in the event that the processor determines that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object,        wherein the processor computes a first vector which extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector which extends from the virtual physical object towards the operator - controlled object; computes an angle formed by the first vector and second vector; and, in the event that the angle falls within a prescribed relationship with regard to a prescribed reference angle, determines that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object.     
     
     
       32. A computer- implemented virtual image generation method which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator - controlled object moving relative to virtual physical objects, the operator - controlled object and the virtual physical objects being defined within a three - dimensional virtual space, the method comprising the steps performed by a computer of:      storing, in a memory, shape data defining shapes of the virtual physical objects;        computing position data of the operator - controlled object with respect to the virtual physical objects;        determining, on the basis of the shape data and the position data, for the operator - controlled object, whether one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlapping state when viewed from the viewpoint;        generating image data for displaying on the monitor the operator - controlled object and the virtual physical objects viewed from the viewpoint, in which a virtual physical object determined to be in an overlapping state is processed so as to be displayed as a show - through image generated in a prescribed pattern through which the operator - controlled object can be viewed in the event that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlapping state when viewed from the viewpoint, and in which the one of the virtual physical objects is determined to be in a state other than the overlapping state is displayed as a non - show - through image;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector that extends from the virtual physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       33. The virtual image generating method of  claim 32 , further comprising:
   storing a status flag indicating whether or not a height of the virtual physical object is such that the operator - controlled object is substantially obscured by the virtual physical object.     
     
     
       34. A memory for use with a virtual image generation apparatus which generates images observed from a viewpoint to be displayed on a monitor, the images including an operator- controlled object moving relative to virtual physical objects, the operator - controlled object and the virtual physical objects being defined within a three - dimensional virtual space, the memory storing a program executable by a processor to perform the steps of:      supplying shape data defining shapes of objects to be displayed;        computing position data of the operator - controlled object with respect to the virtual physical objects;        determining, on the basis of the shape data relating to the virtual physical objects present in the virtual space and the position data, for the operator - controlled object, whether any of the virtual physical objects are located between the viewpoint and the operator - controlled object in an overlapping state when viewed from the viewpoint;        generating image data for displaying on the monitor the operator - controlled object and the objects viewed from the viewpoint, in which any of the virtual physical objects in an overlapping state are processed so as to be displayed as a show - through image generated in a prescribed pattern through which the operator - controlled object can be viewed in the event that any of the virtual physical objects are located between the viewpoint and the operator - controlled object in an overlapping state when viewed from the viewpoint, and in which any of the virtual physical objects disposed in a state other than the overlapping state are displayed as a non - show - through image;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector that extends from the vector physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not any of the virtual physical objects are located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       35. A game device which generates images observed from a viewpoint to be displayed on a monitor, the images including a player- controlled object moving relative to virtual physical objects, the player - controlled object and the virtual physical objects being defined within a three - dimensional virtual space, the game device comprising:      an input means with which a game player operates a computer game;        shape data memory which stores shape data defining shapes of the virtual physical objects present in the virtual space;        a position data specifier which specifies current position data for the player - controlled object with respect to the virtual physical objects;        a processor that determines, on the basis of the shape data and the position data, whether or not one of the virtual physical objects is located between the viewpoint and the player - controlled object; and        an image generator which generates image data for displaying on the monitor screen the player - controlled object and the virtual physical objects viewed from the viewpoint wherein the one of virtual physical objects is processed so as to be displayed as a show - through image generated in a prescribed pattern through which the player - controlled object is viewed in the event that the processor determines that the one of the virtual physical objects is located between the viewpoint and the player - controlled object in an overlapping state when viewed from the viewpoint, and wherein a virtual physical object is displayed without such show - through image effect in the event that the player - controlled object and the one of the virtual physical objects are disposed in a state other than the overlapping state,        wherein the processor computes a first vector that extends in a direction in which the player - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the player - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the one of the virtual physical objects is located between the viewpoint and the player - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       36. A computer system comprising a graphic image processor wherein various objects are defined in a three- dimensional virtual space and programs are executed in response to an operator's instruction so that an operator - controlled object moves relative to virtual physical objects defined in the three - dimensional virtual space and images of the operator - controlled object and the virtual physical objects viewed from a viewpoint are generated for displaying on a monitor, the computer system comprising:      an input means manually controlled by an operator for receiving operator commands to move the image of the operator - controlled object;        shape data memory stored with shape data for objects;        position data specification means for specifying position data of the operator - controlled object with respect to the virtual physical objects;        a processor that determines, on the basis of the shape data and the position data, whether or not one of the virtual physical objects is located between the viewpoint and the operator - controlled object; and        processing means for generating images of the operator - controlled object and the virtual physical objects for displaying on the monitor,        wherein the processor determines positions of the operator - controlled object with respect to the virtual physical objects and, in the event that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in the three - dimensional virtual space when viewed from the viewpoint, generates a portion of the virtual physical object overlapping with the operator - controlled object with a show - through image effect generated in a prescribed pattern, and        the processor computes a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the one of the vector physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       37. The game device of  claim 36 , further comprising:
   a status flag register that stores a status flag indicating whether or not a height of the virtual physical object is such that the operator - controlled object is substantially obscured by the virtual physical object.     
     
     
       38. A computer system defining objects in a three- dimensional virtual space and executing programs that respond to an operator instruction so that an operator - controlled object moves relative to virtual physical objects defined in the three - dimensional virtual space and images of such objects viewed from a viewpoint are generated for displaying on a monitor, the computer system comprising:      an input means manually controlled by an operator for receiving operator commands to move the image of the operator - controlled object;        shape data memory stored with shape data for objects;        position data specification means for specifying position data of the operator - controlled object with respect to the virtual physical objects;        a processor for determining, on the basis of the shape data and the position data, whether or not one of the virtual physical objects is located between the viewpoint and the operator - controlled object; and        a processor for generating images of the operator - controlled object and the virtual physical objects for displaying on a monitor,        wherein the processor for determining determines positions of the operator - controlled object with respect to the virtual physical objects and, in the event that the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in the three - dimensional virtual space when viewed from the viewpoint, generates a portion of the virtual physical object overlapping with the operator - controlled object with a show - through image effect generated in a prescribed pattern, and        the processor for determining computes a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector that extends from the virtual physical object towards the operator - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       39. A computer- implemented method of generating images on a computer system, the computer system defining objects in a three - dimensional virtual space, the objects including an operator - controlled object and virtual physical objects, and wherein the computer system generates images of the objects viewed from a viewpoint for displaying on a monitor, the method comprising the steps performed by a computer of:      receiving signals from an input means controlled by an operator;        processing the signals so that operator - controlled object moves relative to the virtual physical objects in response to the signals;        determining the positions of the operator controlled object with respect to the virtual physical objects;        generating images of the operator - controlled object and the virtual physical objects viewed from the viewpoint for displaying on the monitor,        wherein, in the event that one of the virtual physical objects is located between the viewpoint and the operator - controlled object in the three - dimensional virtual space when viewed from the viewpoint, a portion of the one of the virtual physical objects overlapping with the operator controlled object is generated with a show - through effect generated in a prescribed pattern;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       40. A memory for use with a game provided by a computer system, wherein the game comprises objects in a three- dimensional virtual space, the objects including an operator - controlled object and virtual physical objects, and wherein the computer system generates images of the objects viewed from a viewpoint for displaying on a monitor, the memory storing a program executable by a processor to perform the steps of:      receiving signals from an input means controlled by an operator;        processing the signals so that operator - controlled object moves relative to the virtual physical objects in response to the signals;        determining positions of the operator - controlled object with respect to the virtual physical objects;        generating images of the operator - controlled object and the virtual physical objects viewed from the viewpoint for displaying on the monitor,        wherein, in the event that one of the virtual physical objects is located between the viewpoint and the operator - controlled object in the three - dimensional virtual space when viewed from the viewpoint, a portion of the one of the virtual physical objects overlapping with the operator - controlled object is generated with a show - through effect generated in a prescribed pattern;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       41. A virtual image generation apparatus for a game, wherein the game comprises an operator- controlled object moving relative to virtual physical objects within a three - dimensional virtual space, the virtual image generation apparatus comprising:      shape data memory which stores data defining shapes of a plurality of virtual physical objects within the three - dimensional virtual space;        position data specification means for specifying a position of the operator - controlled object within the virtual space;        a processor for determining whether at least one of the virtual physical objects is located between a viewpoint and the operator - controlled object;        first image generation means for generating image data for the operator - controlled object and the plurality of virtual physical objects as viewed from the viewpoint; and        second image generation means for generating image data for the operator - controlled object and the virtual physical objects in a prescribed pattern if the processor determines that the at least one of the virtual physical objects is located between the viewpoint and the operator - controlled object when viewed from the viewpoint,        wherein the processor computes a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint and a second vector that extends from the at least one of the virtual physical objects towards the operator - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the at least one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       42. A computer- implemented virtual image generation method for a game, wherein the game comprises an operator - controlled object moving relative to virtual physical objects within a three - dimensional virtual space, the method comprising the steps performed by a computer of:      storing, in a memory, data defining shapes of a plurality of virtual physical objects within the three - dimensional virtual space;        computing the position of the operator - controlled object within the virtual space;        determining whether one of the virtual physical objects is located between a viewpoint and the operator - controlled object;        generating image data for the operator - controlled object and the plurality of virtual physical objects as viewed from the viewpoint,        wherein generating image data for the operator - controlled object and at least one of the virtual physical objects is generated in a prescribed pattern if the one of the virtual physical objects is located between the viewpoint and the operator - controlled object when viewed from the viewpoint;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not the at least one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       43. A memory storing a program for a game, wherein the game comprises an operator- controlled object moving relative to virtual physical objects within a three - dimensional virtual space, the program executable by a processor to perform the steps of:      storing data defining shapes of a plurality of virtual physical objects within the three - dimensional virtual space;        computing the position of the operator - controlled object within the virtual space;        determining whether one of the virtual physical objects is located between a viewpoint and the operator - controlled object;        generating image data for the operator - controlled object and the virtual physical objects as viewed from the viewpoint,        wherein generating image data for the operator - controlled object and at least one of the virtual physical objects is generated in a prescribed pattern if the one of the virtual physical objects is located between the viewpoint and the operator - controlled object when viewed from the viewpoint;        computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object;        computing an angle formed by the first vector and the second vector; and        determining whether or not the one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       44. A computer system configured as a game device, wherein the game device comprises an operator- controlled object moving relative to virtual physical objects within a three - dimensional virtual space, the computer system comprising:      a controller for operating the operator - controlled object;        first generating means for generating image data of the operator - controlled object and a plurality of virtual physical objects from a viewpoint,        means for determining the position of the operator - controlled object with respect to the virtual physical objects as viewed from the viewpoint;        second generating means for generating image data for the operator - controlled object and the virtual physical objects in a prescribed pattern if at least one of the virtual physical objects is located between the viewpoint and the operator - controlled object when viewed from the viewpoint; and        a processor for computing a first vector that extends in a direction in which the operator - controlled object is observed from the viewpoint, and a second vector that extends from the virtual physical object towards the operator - controlled object,        wherein the processor computes an angle formed by the first vector and the second vector, and determines whether or not the at least one of the virtual physical objects is located between the viewpoint and the operator - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       45. A game device, wherein the game device comprises a player- controlled object moving relative to virtual physical objects within a three - dimensional virtual space, the game device comprising:      a controller for operating the player - controlled object;        a shape data memory which stores data defining shapes of a plurality of virtual physical objects present in the three - dimensional virtual space;        a position data specifier which specifies a current position for the player - controlled object within the virtual space;        a processor that determines whether at least one of the virtual physical objects is located between a viewpoint and the player - controlled object;        an image generator which generates image data for the player - controlled object and the virtual physical objects as viewed from the viewpoint and image data for the player - controlled object and the virtual physical object in a prescribed pattern if the processor determines that the at least one of the virtual physical objects is located between the viewpoint and the player - controlled object when viewed from the viewpoint,        wherein the processor computes a first vector that extends in a direction in which the player - controlled object is observed from the viewpoint and a second vector that extends from the virtual physical object towards the player - controlled object, computes an angle formed by the first vector and the second vector, and determines whether or not the at least one of the vector physical objects is located between the viewpoint and the player - controlled object in an overlap state when viewed from the viewpoint in accordance with whether the angle falls within a prescribed relationship with a reference angle.     
     
     
       46. The game device of  claim 45 , further comprising:
   a status flag register that stores a status flag indicating whether or not a height of the virtual physical object is such that the operator - controlled object is substantially obscured by the virtual physical object.