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Spent a few hours this past weekend sqeezing every last bit of efficiency out of a starfield generator for Space Survivor.  Fortunately, this was made extremely easy with Richard Lord’s very fine Flint Particle System.

The basic concept:

• Set up 4 particle emitters just outside the 4 edges of the screen
• Feed the Starfield a velocity vector from your ship’s movement engine
• use the velocity vector to give each generated particle a velocity opposite that of the ship
• use the built-in garbage collector of the Flint Particle System to destroy stars that go off screen

There are still some issues with it, like pre-filling the screen with stars, but here’s a demo of it in action.  Code is below the fold:

To use the starfield generator, simply ad the starfield to your stage or a clip with:

Where _width and _height are the width and height of your viewport.
And then in your game loop:

Where velX and velY are the X and Y components of the velocity vector of your Object in Space.
And finally, here is the Starfield Class: