When I set out to write a very simple Pixel Bender (PB) kernel/script thingy, I expected it to be relatively straight-forward, mostly because Adobe has been so good writing quality documentation for its products and/or there is a wealth of info on their products produced by their users. Unfortunately I didn’t find the dev guide in the Help menu and I missed some key AS3 bits from the links I’ll post below, but even so I still had a lot of trouble finding some info that really should already have been out on the interwebs. So this post is to fill in the gaps when going from AS3 to Pixel Bender.
Hope it helps

Best resources for beginners

Here’s the best tutorials and explanations I’ve found so far:

• The official guide and reference. Slap that F1 key! Also, don’t forget the Help menu in the toolkit like I did (there’s the PB-specific language spec and dev guide there).
• Using PB as a calculator. Completes the official tutorial.
• Great in-depth article with general+performance tips.
• Very straight-forward examples + comedy. Can’t go wrong there.
• Nice user article on optimizations and some speed tests (turns out, for input bitmapData beats ByteArray beats Vector.)

Syntax overview

As a casual programmer of high-level languages and no mid- to low-level ones, I was thrown off by PB’s awkward syntax. It’s strongly typed, which is fine, except I’m not familiar with low-level languages like C or any previous shader language (PB is based on GLSL from what I hear). Here’s a basic difference:

AS3: var i:Number = 12;
…in PB is: float i = 12.0;
The decimal in 12.0 tells PB it’s a floating point number. If it was just 12 PB would think it’s an int.

When dealing with “vectors” (which are arrays, as in Flash 10’s odd use of the word “vector”) it’s float2 i = float2(12.0, 2.0). Notice there’s no brackets or anything suggesting any type of array present. It’s simply the type + how big the array is, eg float3. It goes up to 4, for the 4 channels in images: Red, Green, Blue, Alpha). Then, as you can see, intializing the array is a simple matter of putting in the numbers you said would be there. So float4(1.0, 24.2, 0.1, 3.4) is valid whereas float2(1.0, 24.2, 2) is not, because there’s an extra number in there and it’s an int (adding insult to injury).

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