Jozef Chúťka's blog

Pixel Bender for Flash Player lets you play some more advanced games. Based on your needs you can force your kernels to “eat” not only BitmapData, but also ByteArray-s or Vector-s. With this knowledge, you can simply use Pixel Bender kernels for some fast math or processing like 3D engines (3D to 2D projection) etc. Lets have a look at some simple demos, how to push vector and raw bytes directly into shader via ShaderJob:

Vector.<Number>

Simple (one-dimension) vector may be recognized by pixel bender as 3-channel input just as simple as providing correct width/height for shader:

var src:Vector.<Number> = new Vector.<Number>();
while(someLooping)
{
    src.push(x);
    src.push(y);
    src.push(z);
}

var shader:Shader = new Shader(code);
shader.data.src.input = src;
shader.data.src.width = src.length / 3; // forces pixel bender to use image3 as input
shader.data.src.height = 1;

var res:Vector.<Number> = new Vector.<Number>();
var job:ShaderJob = new ShaderJob(shader, res, src.length / 3, 1);
job.start(true);

for(var i:uint=0; i<src.length; i+=3)
{
    x = res[i];
    y = res[i+1];
    z = res[i+2];
}

ByteArray

If you are more in “low-level” things, try using raw bytes as input. Do not forget to setup LITTLE_ENDIAN for source and result variables. Also make sure width*height*4 results in source bytes length.

var src:ByteArray = new ByteArray();
src.endian = Endian.LITTLE_ENDIAN;
src.position = 0;
while(someLooping)
{
    src.writeFloat(x);
    src.writeFloat(y);
    src.writeFloat(z);
}

var shader:Shader = new Shader(code);
shader.data.src.input = src;
shader.data.src.width = 256; // e.g.
shader.data.src.height = src.length/4/256;

var res:ByteArray = new ByteArray();
res.endian = Endian.LITTLE_ENDIAN;

var job:ShaderJob = new ShaderJob(shader, res, 256, src.length/4/256);
job.start(true);

res.position = 0;
for(var i:uint = 0; i<src.length/4; i++)
{
    x = res.readFloat();
    y = res.readFloat();
    z = res.readFloat();
}

Lets have a look at how pixel bender handles input and outputs. As with current version of pixel bender/flash player it seems like:

'res' : cannot have 1 or 2 channel outputs

… but you can use 3 or 4 channel outputs (float3, pixel3).

<languageVersion : 1.0;>
kernel threed <namespace : "sk.yoz";vendor : "Yoz";version : 1;>
{
    input image3 src;
    output float3 res; // or pixel3
    void evaluatePixel()
    {
        res = sample(src, outCoord());
        // we have res.x, res.y and res.z
    }
}

Where to go from here:

• Using Pixel Bender to calculate information
• Number crunching with as3 and pixelbender
• Using Pixel Bender with Flash Builder 4 as a number crunching engine
• Flash 10, Massive amounts of 3D particles with Alchemy (source included).