var irect:Rectangle = rect.intersection(rect2);
Then use irect for the clipRect property of draw(), after some coordinate compensation (and after irect is found to be larger than 1×1). This will make Flash draw ONLY the portion of the clips we’re concerned with, drastically reducing draw time, in most cases (especially when testing big clips against small clips).

Besides calling “new”, draw() has the biggest impact on performance (sometimes more-so, depending on the size of the clip to draw), which is why the gain is so large.

private function i_hitTestCircle2(clip1:Sprite, clip2:Sprite):Boolean
{
	var dx:Number = clip2.x - clip1.x;
	var dy:Number = clip2.y  - clip1.y ;

	var radii:Number = ((clip1.width * .5) + (clip2.width * .5));
	return ((dx * dx) + (dy * dy) < radii * radii);
}

hitTest (50000 iterations)
Player version: MAC 10,1,51,28 (regular)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
hitTest                                                      54     0.00
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
hitTestCircle (50000 iterations)
Player version: MAC 10,1,51,28 (regular)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
hitTestCircle                                               133     0.00
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
hitTestCircle2 (50000 iterations)
Player version: MAC 10,1,51,28 (regular)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
hitTestCircle2                                               56     0.00
–––––––––––––––––––––––––––––––––––––––––––––––

Sure, Box2D actually does the right thing w.r.t collision (and PushButton is integrated with it out of box). Even if you don’t care about the physical response part, the algorithms that Box2D uses to _detect_ collisions are smart and would get you the performance improvement I described.

Before we go 1.0 we are going to do a major code style update to match Flex style (http://code.google.com/p/pushbuttonengine/issues/detail?id=56) as well as reorganize the codebase to make it easier to work with… Our bad. :)

That is a good point. Here is the result with clips that are about 3 times larger:

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
checkBitmapDataHitInternal (10000 iterations)
Uses BitmapData.hitTest to check for collision. BitmapData not cached.
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
[function]                                                 8087     0.81
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
checkBitmapDataHitDynamic (10000 iterations)
Uses BitmapData.hitTest to check for collision. BitmapData not cached. M
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
[function]                                                 1848     0.18
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

Note, that is with cacheAsBitmap set to true.

mike chambers

mesh@adobe.com

You are exactly correct. Setting cacheAsBitmap = true on the author time clips brings the performance to the same level as the dynamic clips.

Here is the relevant section:

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
checkBitmapDataHitDynamic (10000 iterations)
Uses BitmapData.hitTest to check for collision. BitmapData not cached. M
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
[function]                                                 1844     0.18
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
checkBitmapDataHitInternal - cacheAsBitmap (10000 iterations)
Uses BitmapData.hitTest to check for collision. BitmapData not cached.
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
[function]                                                 1805     0.18
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

Ill update the post to reflect this. Good catch.

mike chambers

mesh@adobe.com

Thats not completely true because speed of BitmapData.hitTest is largely depending on the size of objects. For objects with size of only couple of pixels, its lightning-fast. But try objects of hundreds or thousands of pixels and it gets so slow that it cant even finish this test.

Other collision techniques, like math-based or checking bounds, are not affected by the size.

So you cant just compare these results directly.

Feel free to rewrite the circle collision and Ill add it to the test.

Thanks…

mike chambers

mesh@adobe.com