0.9 Slick0190: sprite sheet animation, part 2

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• Preview
• General background information
  • The SpriteSheet class
  • The Animation class
• Discussion and sample code
  • The class named Slick0190
  • The init method
  • The update method
  • The render method
• Run the program
• Summary
• What's next?
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules designed to teach you about the anatomy of a game engine.

Although the modules in this collection will concentrate on the Java game library named Slick2D, theconcepts involved and the knowledge that you will gain is applicable to different game engines written in different programming languages as well.

The purpose of this module is to teach you how to use objects of the SpriteSheet class and the Animation class to perform more complex sprite sheet animations than was the case in the earlier moduletitled Slick0180: Sprite sheet animation, part 1 .

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the imagesand listings while you are reading about them.

Figures

• Figure 1 . The sprite sheet.
• Figure 2 . Sprite running to the right.
• Figure 3 . Sprite answering nature's call.
• Figure 4 . Sprite running to the left.

Listings

• Listing 1 . Beginning of the class named Slick0190.
• Listing 2 . Beginning of the init method.
• Listing 3 . Begin populating the Animation object.
• Listing 4 . Add images from the bottom row of
• Listing 5 . Finish populating the animation object.
• Listing 6 . Beginning of the update method.
• Listing 7 . Compute display locations for first 20 frames.
• Listing 8 . Don't change position for middle group of sprite images
• Listing 9 . Run from right to left.
• Listing 10 . The render method.
• Listing 11 . Source code for Slick0190.

Preview

I will present and explain a program that uses both rows of sprites from the sprite sheet shown in Figure 1 . The program uses a SpriteSheet object and an Animation object to produce an animation of a dog playing and answering nature's call. (Note that the overall sprite sheet image is quite small, and the image shown in Figure 1 was enlarged for this presentation.)

Description of the animation

This animation begins with the sprite running from left to right across the game window. Then the sprite stops on the right side of the game window and answers nature's call. Although it isn't shown here, the sprite turns andfaces left during that process. Then the sprite runs from right to left across the game window. This pattern repeats for as long as the program runs, and is illustrated by the three screen shots that follow.

Sprite running to the right

Figure 2 shows the sprite running from left to right. This is a flipped version of one of the images in the top row of Figure 1 .

Sprite answering nature's call