generate barcode in c# windows application TILE-BASED GAME DESIGN in Font

Paint Code 128 in Font TILE-BASED GAME DESIGN

//Create the cat's bounce vector var bounce_Player:VectorModel = VectorMath.bounce(v1, v0.ln); //Bounce the cat gameObject.vx = bounce_Player.vx; gameObject.vy = bounce_Player.vy; enemySquashed = true; } else { //No collision } return enemySquashed; } This is a distance-based collision check. If the method returns true, _enemySquashed is set to true, and the application class stops blitting the hedgehog and stops checking for a collision.

The squashing effect can be improved with a little explosion when the cat hits the hedgehog. Run the PlayAnimation SWF and squash the hedgehog. You ll see a quick, two-frame cartoon explosion, as shown in Figure 8-27.

The animation is made up of two tiles from the tile sheet. A timer is used to display the tiles 200 milliseconds apart. Each frame of the animation is blitted to the stage, much as we ve been blitting all the other game objects. However, because the animation frames must be displayed persistently on the stage between clicks of the timer, we need to employ a little programming gymnastics. Let s see how it all works. When the code detects a collision between the cat and the hedgehog, it does the following: Captures the hedgehog s x and y positions in explosion_X and explosion_Y variables Starts the _animationTimer, which is set to fire every 200 milliseconds Sends the explosion s x and y values to the playExplosion method Sets the _hedgehogModel to null. if ( _collisionController.enemyCollision (_catModel, _hedgehogModel) ) { //Capture the hedgehog's position _explosion_X = _hedgehogModel.xPos; _explosion_Y = _hedgehogModel.yPos; //Start the timer _animationTimer = new Timer(200); _animationTimer.start(); //Send the explosion's x and y values to the //playExplosion method playExplosion(_explosion_X, _explosion_Y); //Null the hedgehog _hedgehogModel = null; } The playExplosion method blits each frame of the animation from the tile sheet. It does so while the timer s currentCount property is less than the number of animation frames. currentCount is a built-in property of the Timer class that tells you how many times the timer has fired. It counts each tick of the clock. When the currentCount property is greater than the number of animation frames, it stops the timer and sets the _explosion flag to false. private function playExplosion(x:Number, y:Number):void { //The number of frames in the animation var animationFrames:uint = 2;

//Animate while the _animationTimer's currentCount //is less than the number of frames in the animation. The first //frame will be 0 , the second will be 1 if(_animationTimer.currentCount < animationFrames) { //Find the tiles on the third row of the tile sheet var sourceRectangle:Rectangle = new Rectangle ( _animationTimer.currentCount * MAX_TILE_SIZE, 3 * MAX_TILE_SIZE, MAX_TILE_SIZE, MAX_TILE_SIZE ); //The point on the stage where the animation should //be displayed. This will be the same as the //hedgehog's original position var destinationPoint:Point = new Point(x, y); _foregroundBitmapData.copyPixels ( _tileSheetBitmapData, sourceRectangle, destinationPoint, null, null, true ); } //If the maximum number of animation frames //has been reached, stop the _animationTimer //and set the _explosion variable to false else { //Stop and reset the timer _animationTimer.stop(); } } This is a pretty straightforward blit display system, but how does it know which tiles to use for the animation Figure 8-28 shows the two tiles in the tile sheet that are used as frames in the animation. They re both on row 3, and the first one is at column 0. This is important, so keep it in mind as I explain how these tiles are found.

Figure 8-28. The animation frames start at column 0, row 3. Here s the section of code that finds the correct position on the tile sheet: var sourceRectangle:Rectangle = new Rectangle ( _animationTimer.currentCount * MAX_TILE_SIZE, 3 * MAX_TILE_SIZE, MAX_TILE_SIZE, MAX_TILE_SIZE ); Remember that a Rectangle object s constructor arguments are as follows: ( x position, y position, width, height ); The x position in this case refers to the position of the tile on the tile sheet: _animationTimer.currentCount * MAX_TILE_SIZE The value of currentCount will be zero when the timer first starts. That means you can read the preceding line of code like this: 0 * 64