A method is provided for displaying a video game character traversing a video game playfield, for use with a system which includes a video screen display, a user-controlled graphics controller and digital memory; wherein the video game character follows a path within the playfield, the method comprising the steps of: storing multiple collision blocks that define respective path segments; dividing the playfield into multiple path blocks that comprise the path; storing character collision-type information; storing references from individual path blocks to individual collision blocks; displaying character movement through the playfield from path block to path block along the path in response to user input to the graphics controller; controlling the display of character movement by causing the character image to follow a path defined by the path segments of individual collision blocks; and changing the stored character collision-type information when the character path passes a prescribed location on the playfield.
Yuji Naka, Masanobu Yamamoto
Original Assignee: Sega of America, Inc.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to video games, and more specifically, to video games that employ a playfield that scrolls relative to a game character in order to show character motion through the playfield.
2. Description of the Related Art
Video games are well known in which a game character, or sprite, follows a prescribed path through a scrolled playfield in response to the commands of a user who is playing the game. The user operates an input device which includes a control console which may include a "joy stick" used to control character movement. A user command issued through the input device for the character to move right results in the playfield scrolling to the left which creates the impression that the character is moving to the right relative to the playfield. Conversely, a user command for the character to move left results in the playfield scrolling to the right which creates the impression that the character is moving to the left. During such scrolling the character image ordinarily remains fixed near the center of the screen display despite the appearance of movement relative to the playfield.
In typical video games, the input device permits the user to command the character to perform numerous activities such as to jump or to crouch down or to speed-up or to slow-down. Often, a game character takes on different appearances as it engages in different activities. For example, when the character moves at slower speeds, its legs, arms and torso may be fully visible as the playfield scrolls slowly. However, when the character speeds up, most of the character image may be portrayed as a blur with only the character head being fully recognizable while the playfield scrolls rapidly. Moreover, the character may have one portrayal when it crouches and another portrayal when it jumps. Additionally, there may be special character antics that involve a series of images, such as tumbling, throwing a kick or "flying" through the air.
A challenge associated with implementing such video games is to produce a playfield which has a variety of images and obstacles. For example, there may be mountains to climb, canyons to jump over or enemies to defeat. In the midst of all of this activity, changes in the appearance and movements of the character and the playfield must occur smoothly and quickly so as not to distract the user or detract from the excitement of a high speed action packed video game.
Consequently, certain uniform techniques often are employed to control the movement and appearance of game characters and the playfield. These techniques include defining a path to be followed by the character through the playfield. The character moves along the path in response to user commands. For example, if the path ascends to the right, and the user commands the character to move to the right, then the character is depicted climbing the path to the right as the playfield scrolls to the left. If the user subsequently commands the character to move back towards the left, then the character will be shown descending the path to the left as the playfield scrolls to the right.
The image of the character moving along the path is produced under the control of a computer program. Character movement is constrained by the program such that as the character moves left or right, it always tries to maintain contact with the path. If the character jumps, for example, it soon returns (falls) to the path. If the path includes a discontinuity such as an on-screen image of a cliff, for example, then a character running off the edge of the cliff might fall to another path at the base of the cliff; or it might jump across the chasm at the edge of the cliff and land on a path opposite the cliff. The user controls character movement, but the program ensures that the character generally follows the path.
While paths through the playfield generally have been an acceptable way to constrain character movement, there have been shortcomings with there use. For example, a typical earlier method for making sure that a character follows the path is to use collision blocks. As the character moves in response to user commands, a computer program references stored collision blocks to determine the exact path to be followed in response to such commands. Specifically, the playfield is divided into graphics blocks. As the character traverses individual graphics path blocks, a path control program references individual collision blocks that correspond to such graphics path blocks. A collision block is used to determine, for example, whether the path within a graphics path blocks is level, inclined or drops off a cliff.
A problem associated with such earlier methods is that it may be desirable to define two different paths through the same region of a graphics path block. Unfortunately, a collision block typically defines only a single path, and each graphics path block corresponds to only one collision block. Therefore, it has been difficult to provide multiple paths through the same region of a graphics path block.
Thus, there has been a need for improved techniques which permit multiple paths through the same region of a graphics path block. The present invention meets these needs.
SUMMARY OF THE INVENTION
In one aspect, the invention involves a method for displaying a video game character traversing a video game playfield, for use with a system which includes a video screen display, a user-controlled graphics controller and digital memory. The playfield is displayed as a series of scrolled screen displays. The video game character follows a path within the playfield. The progress of the game character in traversing the playfield is indicated by scrolling the playfield relative to the game character.
Multiple collision blocks used to define respective path segments are stored in digital memory. The playfield is divided into multiple graphics path blocks that comprise the path. Stored character collision type information indicates whether a particular character is to be regarded as either a first character collision type or a second character collision type. References are provided from individual graphics path blocks to individual collision blocks. At least one reference is dependent upon the character collision type of a character traversing a particular graphics path block. Character movement through the playfield in response to user input to the graphics controller is displayed on the screen display. The displayed character image follows a path defined by the path segments of individual collision blocks referenced to individual graphics path blocks that comprise the path. The stored character collision type information is changed when the character passes a prescribed location on the playfield such that after the change, the stored character collision type information indicates a different character collision type than before the change.
Therefore, for example, the character is able to follow a path that crosses over itself. As the character approaches the cross-over a first time, it stores one type of collision information, and it follows one branch of the cross-over without colliding with the other branch. As the character approaches the cross-over a second time, it stores another type collision information, and it follows another branch of the cross-over without colliding with the first branch.
These and other purposes and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description in conjunction with the appended drawings in which: