When iterating through an array that was generated by some built-in function (such as getVector()), check to make sure you’re rounding the input first. If you get an “out of range” error but your code is fucking perfect, then it’s probably because the rectangle used as input by getVector is skipping a row of pixels because the x,y of said rectangle is being rounded UP. For example, 12.51 becomes 13 but since the rectangle is limited by certain dimensions it simply (stupidly, moronically, fucking ridiculously) truncates the dimensions by one row or column. So when it turns the pixel data into a 1D array it’s missing a whole chunk of data which causes your pre-computed (with the correct dimensions) array length to be too high… hence the iterator will hit a number outside the array’s range.

Judging by the number of results Google returns, this is a pretty fringe case (that or I’m exceptionally stupid… hush). Regardless, it’s a problem that has been plaguing me for the past few months. If it weren’t for my genius programmery brother I would have never found it either. But thanks to him I’m now savvy to what’s termed as “rounding errors”. They even sound evil.

Here’s an example with code…
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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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Makin’ games

I’ve been working on a couple game concepts and want to prototype a few more before committing to one to build out. I’ve been hacking the hell out of Flixel, which I’ve decided to use for a most of the games. There’s a screenshot of game3 on the right there. Weird, eh? Also fugly, but it’s placeholder art so there. I have a new collision detection system for it that I’ll be posting about eventually (at least, I’ve never heard of it before).

The microtransaction (MTX) dilemma

I’m really excited about all the new services that have been released to allow Flash developers to monetize their games through microtransactions. I fucking hate ads, plus the ROI of them in Flash games is usually shit. Many many years ago I knew microtransactions (MTX) were the future of digital content and I’m pleased to see the idea coming to the mainstream (in America at least, Asia was quicker on it as usual).

The problem I’m seeing with MTX is that Flash developers need to try a lot harder by making much bigger games in order to really reap the rewards. Before, you could make a pretty simple, fun and addictive game and monetize it easily with ads. But with MTX, you can’t do that as easily since you need to build more content for players to buy into. For example, to me, putting premium content in a Tower Defense game isn’t viable–the game concept is so small that I doubt anyone is going to pay anything for more turrets or maps (for example). There just isn’t enough game there.

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