Which one executes faster: hitTestObject or Point.distance? - actionscript-3

Question

I am trying to optimize my collision detection alghorithm written in AS3.
I am wondering if there is any improvements in performance if I use
Point.distance(pointObject1, pointObject2);
between two objects instead of using
object1.hitTestObject(object2);
My objects are all more or less convex so the border doesn't really matter.

Answer 1

Point.distance is much more faster (4 and more times!) if your test objects are complicated containers with several children inside. If you use simple Sprite's it'll be only near 25% difference in functions execution time.
It's so, because Point.distance is just counting a hypotenuse from Pythagoras' theorem. So, we've got only 2 subtractions, 1 addition and 3 involutions to count. Many modern processors have involution instruction, so it's fast. If we use hitTest, there are much more actions to be performed. And the number of these actions will grow with the complexity of hitTest'ing Sprite (because it's harder to count it's bounds).
I've just made some tests. The result confirmed that I was right.
var ar:Vector.<Sprite> = Vector.<Sprite>([]); //Sprites for hitTest
for(var i:int = 0; i < 100000; i++) {
var sp:Sprite = new Sprite(); //!The results will be other, is case of use a huge container with come objects here!
sp.graphics.drawCircle(0, 0, randomIntBetween(1, 200)); //add some shapes
sp.graphics.drawRect(0, 0, randomIntBetween(1, 200), randomIntBetween(1, 200));
sp.x = randomIntBetween(-800, 800);
sp.y = randomIntBetween(-800, 600);
sp.rotation = randomIntBetween(-360, 360); //rotate and scale in random way
sp.scaleX = sp.scaleY = Math.random();
ar.push(sp);
}
var tim:Number = new Date().time;
for each(var spr:Sprite in ar) {
ar[0].hitTestObject(spr);
}
tim = new Date().time - tim;
trace(tim);
var pn:Vector.<Point> = Vector.<Point>([]); //Points for Point.distance
for(i = 0; i < 100000; i++) {
var point:Point = new Point(randomIntBetween(-800, 800), randomIntBetween(-800, 800));
pn.push(point);
}
tim = new Date().time;
for each(var pnt:Point in pn) {
Point.distance(pn[0], pnt);
}
tim = new Date().time - tim;
trace(tim);

Answer 2

Actually, you can't compare those two with each other. If all your objects are single-pixel bitmaps the distance test would work fine. But I imagine that is not the case.
hitTestObject essentially checks the bounding rectangles of the objects, so it's pretty fast.
You could always check the distance to see if they're close enough before doing a pixel level check, because it's more expensive and you don't want to do it too much.
The distance check is great for when you set up circular bounds around an object and determining that two such circles do not intersect. If they do intersect then you have to do another check with hitTestObject to ensure the two object shapes actually overlap. So essentially you would use both, the distance check as a first pass check and hitTestObject as a follow up for accuracy.