Daniel R.

Given that pixel bender is boundless (i.e. defined over an infinite plane of discrete pixel coordinates) I had to introduce the notion of a border pixel to make handling edge cases easier. Since most of the area in a generation is dead I decided to use white for a pixel that is dead (easier on the eyes) and black for a pixel that was alive. My initial attempt at the algorithm ran into a bug with the kernel export for Flash Player feature. After some rewriting I had a working pixel bender kernel that implemented the logic (albeit unoptimized):

<languageVersion : 1.0;>
// $Id: GameOfLife.pbk 57 2008-09-16 02:55:33Z danielr $
kernel GameOfLife
<   namespace : "Daniel Rinehart";
vendor : "NeoPhi.com";
version : 1;
description : "Conway's Game of Life";
>
{
    input image4 src;
    output pixel4 dst;

    void
    evaluatePixel()
    {
        pixel4 border = pixel4(1.0, 0.0, 0.0, 1.0);
        pixel4 dead = pixel4(1.0, 1.0, 1.0, 1.0);
        pixel4 alive = pixel4(0.0, 0.0, 0.0, 1.0);

        pixel4 me = sampleNearest(src, outCoord());

        // default to no change in pixel
        dst = me;

        // I would like to write "all(equal(border, me))" but that's buggy in Flash
        if (!((border.r == me.r) && (border.g == me.g) && (border.b == me.b)))
        {
            int aliveNeighborCount = 0;
            float2 offset = float2(pixelSize(src).x, pixelSize(src).y);

            // Find out how many of my neighbors are alive
            // left
            pixel4 test = sampleNearest(src, outCoord() + (offset * float2(-1.0, 0.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // upper left
            test = sampleNearest(src, outCoord() + (offset * float2(-1.0, -1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // up
            test = sampleNearest(src, outCoord() + (offset * float2(0.0, -1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // upper right
            test = sampleNearest(src, outCoord() + (offset * float2(1.0, -1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // right
            test = sampleNearest(src, outCoord() + (offset * float2(1.0, 0.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // lower right
            test = sampleNearest(src, outCoord() + (offset * float2(1.0, 1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // down
            test = sampleNearest(src, outCoord() + (offset * float2(0.0, 1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }
            // lower left
            test = sampleNearest(src, outCoord() + (offset * float2(-1.0, 1.0)));
            if ((alive.r == test.r) && (alive.g == test.g) && (alive.b == test.b))
            {
                aliveNeighborCount++;
            }

            // As per: http://en.wikipedia.org/wiki/Conway%27s_Game_of_Life
            // 1. Any live cell with fewer than two live neighbours dies, as if by loneliness.
            // 2. Any live cell with more than three live neighbours dies, as if by overcrowding.
            // 3. Any live cell with two or three live neighbours lives, unchanged, to the next generation.
            if (((alive.r == me.r) && (alive.g == me.g) && (alive.b == me.b)) && ((aliveNeighborCount < 2) || (aliveNeighborCount > 3)))
            {
                dst = dead;
            }
            // 4. Any dead cell with exactly three live neighbours comes to life.
            if (((dead.r == me.r) && (dead.g == me.g) && (dead.b == me.b)) && (aliveNeighborCount == 3))
            {
                dst = alive;
            }
        }
    }
}

Now with a working filter I used some of the recent posts by Mike Chambers on how to embed a pixel bender kernel into MXML. However, since I wasn't using it as a filter and wanted more control over the flow I leveraged the ShaderJob class.

var shader:Shader = new Shader(new gameOfLife() as ByteArray);
shader.data.src.input = current;
var result:BitmapData = new BitmapData(current.width, current.height);
var shaderJob:ShaderJob = new ShaderJob(shader, result, current.width, current.height);
shaderJob.addEventListener(ShaderEvent.COMPLETE, handleShaderDone);
shaderJob.start();

Slap a minimal UI around it and you have (click to launch, view-source enabled, Flash Player 10 required):