Question

I’m working a game.

The game requires entities to analyse an image and head towards pixels with specific properties (high red channel, etc.)

I’ve looked into Pixel Bender, but this only seems useful for writing new colors to the image. At the moment, even at a low resolution (200×200) just one entity scanning the image slows to 1-2 Frames/second.

I’m embedding the image and instance it as a Bitmap as a child of the stage. The 1-2 FPS situation is using BitmapData.getPixel() (on each pixel) with a distance calculation beforehand.

I’m wondering if there’s any way I can do this more efficiently… My first thought was some sort of spatial partioning coupled with splitting the image up into many smaller pieces.

I also feel like Pixel Bender should be able to help somehow, however I’ve had little experience with it.

Cheers for any help.
Jonathan

Answer 1

Let us call the pixels which entities head towards “attractors” because they attract the entities.

You describe a low frame rate due to scanning for attractors. This indicates that you may possibly be scanning an image at every frame. You don’t specify whether the image scanned is static or changes as frequently as, e.g., a video input. If the image is changing with every frame, so that you must re-calculate attractors somehow, then what you are attempting is real-time computer vision with the ABC Virtual Machine, please see below.

If you have an unchanging image, then the most important optimization you can make is to scan the image one time only, then save a summary (or “memoization”) of the locations of the attractors. At each rendering frame, rather than scan the entire image, you can search the list or array of known attractors. When the user causes the image to change, you can recalculate from scratch, or update your calculations incrementally — as you see fit.

If you are attempting to do real-time computer vision with ActionScript 3, I suggest you look at the new vector types of Flash 10.1 and also that you look into using either abcsx to write ABC assembly code, or use Adobe’s Alchemy to compile C onto the Flash runtime. ABC is the byte code of Flash. In other words, reconsider the use of AS3 for real-time computer vision.