Creating an Optimized Post-Retro Game - The Essential Guide to Flash Games - page 516

dispatchEvent(new CustomEventSound(CustomEventSound.PLAY_SOUND,

Main.SOUND_PLAYER_SHOOT, false, 0, 8, 1));

tempProjectile = projectileManager.projectilePool.pop();
var projectileRadians:Number = (player.frame / 360) * 6.28;

//+ 16 to get it to the center of a 32x32 sprite
tempProjectile.x=(player.point.x+16)+Math.cos(projectileRadians);

tempProjectile.y =(player.point.y+16) + Math.sin(projectileRadians);

tempProjectile.x = player.x+16;
tempProjectile.y = player.y + 16;
tempProjectile.nextX = tempProjectile.x;
tempProjectile.nextY = tempProjectile.y;

tempProjectile.dx = rotationVectorList[player.frame].x;
tempProjectile.dy = rotationVectorList[player.frame].y;

tempProjectile.speed = 5;
tempProjectile.frame = 0;
tempProjectile.bitmapData = tempProjectile.animationList[0];
projectileManager.projectiles.push(tempProjectile);
projectileManager.lastProjectileShot=0;
}else {
projectileManager.lastProjectileShot+=step;
}
The preceding function is the actual entire projectile firing code. We only need be concerned with
these two lines:
tempProjectile.dx = rotationVectorList[player.frame].x;
tempProjectile.dy = rotationVectorList[player.frame].y;
The player object's current frame index is the rotated BitmapData in the player.animationList
array that represents the player's current rotated direction. The projectiles pull their dx and dy
values from the rotationVectorList array using the same index using the x value for dx and the
y value for dy .

Optimizing screen-based blit scrolling with
ScrollRect
There are many ways to scroll a screen when programming in AS3. In the previous chapter, we
looked at tile-based blit rendering over a 360-degree scrolling playfield. In this chapter, we will
look at an optimized method to scroll a screen that is not necessarily made up of tiles (although it
could be). We are going to draw all of our assets for the game as vector shapes, add some
simple glow filters, and cache those as BitmapData . We will draw all of these game objects to a
world-sized Bitmapdata canvas, but only display the current viewable window to the user. We will
scroll our screen using a different method than the Camera2D class from Chapter 10.
In our experience, the fastest way to scroll a bitmap screen in AS3 is to use the scrollRect
Rectangle property of the Bitmap instance that holds our world canvas. We simply change the x