Hands-On Optimization - Collisions

[TiefighT]

Howdy,

The stickied optimization thread has some great stuff in it, but I always learn better when I get my hands dirty. The point of this thread is to give a place for everyone to actually go in and see if they can optimize working code (or at least watch other people go in and optimize working code ).

I'm obviously focusing on collision detection here, and for our first run at it I figured we could start with the most straight-forward method I can think of - each object handling its own movement and detection. I'm all for looking at the other approaches (centralized handling w/ bookeeping, tilebased, etc.), but ya gotta start somewhere .

So without furter adeu...

De-Centralized Method
Basic Description
Each square calls a central function to preform it's collision detection and movement on enterFrame. I've taken all the steps I can think of to remove any redundant checks (squares only check for collisions with objects created after themselves, if they have a collision, they tell the other square to skip it's check, etc.). Regardless, its all pretty basic, so I am sure there is plenty of room for improvement.

Examples
Note - either use the .html or download the .swf and open it in the standalone player for the most consistent results (prevents scaling).

Instructions
*Upper Left Button - Adds a square
*Upper Right Button - Removes a square
*Lower left text - maximum velocity (changable)
*Lower right text - current FPS

Full collision detection: .html .swf
This one has everything turned on.
With 30 objects on screen, my FPS stays around 29-30.

No Physics: .html .swf
Same basic idea, but I commented out the meat of the object-object calculations (still goes through the loops, just doesn't do anything inside of them).
With 30 on screen, I get about 38 fps, which means the physics crap is taking some decent calculation time

Walls Only: .html .swf
This time I skip the object-object checks completely.
I can get a crapload (90-100ish) of objects on the screen before FPS takes a hit.

"Optimized" Full Collision: .html .swf
On this one I went through and stored off any object references (i.e. "object._x") to a variable which I used in place of the actual reference whenever possible. The end result was the FPS taking a severe nose dive to around...
30 objects on screen, 22ish FPS.
Fun stuff :/

.FLA source: Click Me
Just what it sounds like, the original .FLA. This version does not have any of the optimization stuff I did in the last example (since it didn't help FPS, I didn't see much of a point). As for the content, pretty much everything of importance is in frame 1 of the Actions level, main timeline.

Let me know and I'll go through and explain what I did in the code in more depth.

So whadaya say?

Edit: Oh yah, and I am using Flash 5 (doing it from the home machine), sorry for any inconvenience :/