Game machine and game program

• US 20030216175A1
• Filed: 11/06/2002
• Published: 11/20/2003
• Est. Priority Date: 05/16/2002
• Status: Active Grant

• Current Assignee: Nintendo Company Limited
• Original Assignee: Nintendo Company Limited
• Inventors: Osako, Satoru, Morimura, Naoya
• Granted Patent: US 7,104,891 B2
• Time in Patent Office: Days
• US Class Current: 463/31
• CPC Class Codes: A63F 13/10 Control of the course of the game, e.g. start, progess, end
• CPC Class Codes: A63F 13/45 Controlling the progress of the video game
• CPC Class Codes: A63F 13/52 involving aspects of the displayed game scene
• CPC Class Codes: A63F 2300/66 for rendering three dimensional images
• CPC Class Codes: A63F 2300/6646 for the computation and display of the shadow of an object or character
• CPC Class Codes: G06T 15/60 Shadow generation

Abstract

A partial shadow volume having a predetermined height defined by a contour of a character object and light coming from a light source is formed based on undulations of a land object, and is then stored in advance in a DVD-ROM 300 or the like. A CPU 10 reads this partial shadow volume for placing the partial shadow volume at a point of intersection of the land object and a line extending from character object placement coordinates to a light direction. The placed partial shadow volume is rendered by using the stencil buffer 16. Based on values in the stencil buffer 16, a shadow of the character object cast on the land object is rendered. Thus, a realistic shadow can be rendered with processing load required for shadow rendering processing being reduced.

Claims

1. A game machine for carrying out game processing to display a state in which a first object casts a shadow formed by light from a light source on a second object in a virtual three-dimensional game space, the game machine comprising:

partial shadow volume storage means for storing a partial shadow volume formed based on a contour of the first object and a direction of the light from the light source and having a predetermined height in the direction of the light based on undulations of the second object;

partial shadow volume placing means for placing the partial shadow volume at shadow volume placement coordinates; and

shadow rendering means for rendering the shadow of the first object cast on the second object based on the partial shadow volume placed by the partial shadow volume placing means.

2. The game machine according to claim 1, wherein

the partial shadow volume placing means further includes shadow volume placement coordinates calculating means for calculating, as the shadow volume placement coordinates, a point of intersection of a line extending from predetermined coordinates on the first object in the direction of the light and the second object.

3. The game machine according to claim 1, wherein

the height of the partial shadow volume is determined so that, even when a shadowed area of the second object cast with the shadow of the first object is arbitrarily varied in the course of a game, the entire shadowed area is always included inside the partial shadow volume.

4. The game machine according to claim 1, wherein

the height of the partial shadow volume is defined by a first height in a direction toward the light source with reference to the shadow volume placement coordinates and a second height in a direction away from the light source with reference to the shadow volume placement coordinates, and

the first height and the second height are determined so that, even when a shadowed area of the second object cast with the shadow of the first object is arbitrarily varied in the course of a game, the entire shadowed area is always included inside the partial shadow volume, and that the first height and the second height are minimum.

5. The game machine according to claim 4, wherein

the first height is determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game in the direction toward the light source with reference to the shadow volume placement coordinates, and

the second height is determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game in the direction away from the light source with reference to the shadow volume placement coordinates.

6. The game machine according to claim 4, wherein

the first height and the second height are commonly determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game.

7. The game machine according to claim 1, wherein

the partial shadow volume storage means stores the partial shadow volume formed in advance of the game processing based on the undulations of the second object.

8. The game machine according to claim 1, further comprising:

maximum undulation calculating means for calculating a maximum undulation of a shadowed area of the second object cast with the shadow of the first object; and

partial shadow volume generating means for generating the partial shadow volume having a height corresponding to the maximum undulation calculated by the maximum undulation calculating means, and causing the partial shadow volume to be stored in the partial shadow volume storage means.

9. The game machine according to claim 8, wherein

the maximum undulation calculating means detects maximum coordinates of the shadowed area that are furthest from the shadow volume placement coordinates in the direction toward the light source and minimum coordinates of the shadowed area that are furthest from the shadow volume placement coordinates in the direction away from the light source, and determines the height of the partial shadow volume based on the detected maximum coordinates and the detected minimum coordinates.

10. The game machine according to claim 9, further comprising contour polygon storage means for storing a contour polygon corresponding to a contour of the first object projected in the direction of the light, wherein

the maximum undulation calculating means detects the maximum coordinates and the minimum coordinates by placing the contour polygon at the shadow volume placement coordinates, and then shifting the contour polygon to the direction of the light and the direction opposite from the direction of the light.

11. The game machine according to claim 10, further comprising contour polygon generating means for generating the contour polygon based on the contour of the first object and the light coming from the light source, and causing the contour polygon to be stored in the contour polygon storage means.

12. A game program to be executed on a game machine for carrying out game processing to display a state in which a first object casts a shadow formed by light from a light source on a second object in a virtual three-dimensional game space, the game program to cause the game machine to execute steps comprising:

reading a partial shadow volume formed based on a contour of the first object and a direction of the light from the light source and having a predetermined height in the direction of the light based on undulations of the second object;

placing the partial shadow volume at shadow volume placement coordinates; and

rendering the shadow of the first object cast on the second object based on the partial shadow volume placed in partial shadow volume placing step.

13. The game program according to claim 12, wherein

the partial shadow volume placing step further includes a step of calculating, as the shadow volume placement coordinates, a point of intersection of a line extending from predetermined coordinates on the first object in the direction of the light and the second object.

14. The game program according to claim 12, wherein

the height of the partial shadow volume is determined so that, even when a shadowed area of the second object cast with the shadow of the first object is arbitrarily varied in the course of a game, the entire shadowed area is always included inside the partial shadow volume.

15. The game program according to claim 12, wherein

the height of the partial shadow volume is defined by a first height in a direction toward the light source with reference to the shadow volume placement coordinates and a second height in a direction away from the light source with reference to the shadow volume placement coordinates, and

the first height and the second height are determined so that, even when a shadowed area of the second object cast with the shadow of the first object is arbitrarily varied in the course of a game, the entire shadowed area is always included inside the partial shadow volume, and that the first height and the second height are minimum.

16. The game program according to claim 15, wherein

the first height is determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game in the direction toward the light source with reference to the shadow volume placement coordinates, and

the second height is determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game in the direction away from the light source with reference to the shadow volume placement coordinates.

17. The game program according to claim 15, wherein

the first height and the second height are commonly determined based on a maximum undulation of the shadowed area that is arbitrarily varied in the course of the game.

18. The game program according to claim 12, wherein

in the partial shadow volume reading step, the partial shadow volume formed in advance of the game processing based on the undulations of the second object is read.

19. The game program according to claim 12, to cause the game machine to further execute steps comprising:

calculating a maximum undulation of a shadowed area of the second object cast with the shadow of the first object; and

generating the partial shadow volume having a height corresponding to the maximum undulation calculated in the maximum undulation calculating step, temporarily storing the partial shadow volume, and causing the partial shadow volume to be read in the partial shadow volume reading step.

20. The game program according to claim 19, wherein

in the maximum undulation calculating step, maximum coordinates of the shadowed area that are furthest from the shadow volume placement coordinates in the direction toward the light source and minimum coordinates of the shadowed area that are furthest from the shadow volume placement coordinates in the direction away from the light source are detected, the height of the partial shadow volume is determined based on the detected maximum coordinates and the detected minimum coordinates.

21. The game program according to claim 20, to cause the game machine to further execute a step of reading a contour polygon corresponding to a contour of the first object projected in the direction of the light, wherein

in the maximum undulation calculating step, the maximum coordinates and the minimum coordinates are detected after the contour polygon is placed at the shadow volume placement coordinates and then the contour polygon is shifted to the direction of the light and the direction opposite from the direction of the light.

22. The game program according to claim 21, to cause the game machine to further execute a step of generating the contour polygon based on the contour of the first object and the light coming from the light source, temporarily storing the contour polygon, and causing the contour polygon to be read in the contour polygon reading step.