Game system and game program

• US 20030228905A1
• Filed: 04/08/2003
• Published: 12/11/2003
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: Nintendo Company Limited
• Original Assignee: Nintendo Company Limited
• Inventors: Osako, Satoru
• Granted Patent: US 6,971,957 B2
• Time in Patent Office: Days
• US Class Current: 463/32
• 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 DVD-ROM 300 previously stores a plurality of shadow volume data corresponding to respective attitudes of an object which casts a shadow. A CPU 10 sets a shadow volume corresponding to the attitude of the object by performing interpolation based on the shadow volume data as necessary. Based on the thus-set shadow volume, a GPU 11 performs determination regarding a shadow region by using a stencil buffer 16. Based on the determination results, the GPU 11 updates luminance information of each pixel stored in a color buffer 14. According to this configuration, in the case where a game apparatus uses the shadow volume to draw a shadow, it is possible to reduce the processing load caused by setting the shadow volume while drawing a more realistic shadow corresponding to the attitude of the object which casts a shadow.

Claims

1. A game system for displaying a shadow of an object in a three-dimensional game space by using a shadow volume, the game system comprising:

attitude changing means for changing an attitude of the object;

first shadow volume data storing means having previously stored therein first shadow volume data corresponding to a first attitude of the object;

second shadow volume data storing means having previously stored therein second volume data corresponding to a second attitude of the object which is different from the first attitude;

shadow volume setting means for setting the shadow volume based on the first shadow volume data when the attitude of the object, which is changed by the attitude changing means, at a certain point in time is identical to the first attitude and for setting the shadow volume based on the second shadow volume data when the attitude of the object at the certain point in time is identical to the second attitude; and

shadow drawing means for drawing a shadow of the object at the certain point in time based on the shadow volume set by the shadow volume setting means.

2. The game system according to claim 1, wherein the shadow volume setting means sets the shadow volume by interpolation based on the first shadow volume data and the second shadow volume data when the attitude of the object at the certain point in time is different from both the first attitude and the second attitude.

3. The game system according to claim 2, wherein the interpolation is linear interpolation.

4. The game system according to claim 1, wherein the second shadow volume data is offset data referencing the first shadow volume data.

5. The game system according to claim 1, wherein:

the attitude changing means rotates the object about a prescribed axis in an object coordinate system;

the second attitude is an attitude of the object rotated around the prescribed axis by a certain angle from the first attitude; and

the shadow volume setting means sets the shadow volume based on the angle of rotation of the object around the prescribed axis.

6. The game system according to claim 5, wherein when the attitude of the object at the certain point in time is equal to the third attitude which is in a prescribed relationship to the first attitude, the shadow volume setting means sets the shadow volume by using the first shadow volume data, which is left unchanged or is suitably changed, as shadow volume data corresponding to the third attitude.

7. The game system according to claim 6, wherein shapes of the object are symmetric with respect to a plane including the prescribed axis.

8. The game system according to claim 6, wherein the third attitude is an attitude of the object rotated around the prescribed axis by 180°

from the first attitude.

9. A game program executed by a computer in a game apparatus for displaying a shadow of an object in a three-dimensional game space by using a shadow volume, the game program causing the computer to execute:

an attitude changing step for changing an attitude of the object;

a first shadow volume data reading step for reading a previously stored first shadow volume data corresponding to a first attitude of the object;

a second shadow volume data reading step for reading a previously stored second shadow volume data corresponding to a second attitude of the object which is different from the first attitude;

a shadow volume setting step for setting the shadow volume based on the first shadow volume data when the attitude of the object, which is changed by the attitude changing step, at a certain point in time is identical to the first attitude and for setting the shadow volume based on the second shadow volume data when the attitude of the object at the certain point in time is identical to the second attitude; and

a shadow drawing step for drawing a shadow of the object at the certain point in time based on the shadow volume set by the shadow volume setting step.

10. The game program according to claim 9, wherein when the attitude of the object at the certain point in time is different from both the first attitude and the second attitude, the shadow volume setting step sets the shadow volume by interpolation based on the first shadow volume data and the second shadow volume data.

11. The game program according to claim 10, wherein the interpolation is linear interpolation.

12. The game program according to claim 9, wherein the second shadow volume data is offset data referencing the first shadow volume data.

13. The game program according to claim 9, wherein:

the attitude changing step rotates the object about a prescribed axis in an object coordinate system;

the second attitude is an attitude of the object rotated around the prescribed axis by a certain angle from the first attitude; and

the shadow volume setting step sets the shadow volume based on the angle of rotation of the object around the prescribed axis.

14. The game program according to claim 9, wherein when the attitude of the object at the certain point in time is equal to the third attitude which is in a prescribed relationship to the first attitude, the shadow volume setting step sets the shadow volume by using the first shadow volume data, which is left unchanged or is suitably changed, as shadow volume data corresponding to the third attitude.

15. The game program according to claim 14, wherein shapes of the object are symmetric with respect to a plane including the prescribed axis.

16. The game program according to claim 14, wherein the third attitude is an attitude of the object rotated around the prescribed axis by 180°

from the first attitude.