Forums → Programming Forum → How to make a perfect hitTest in as2?

The reason is that in flash, the hitTest function only detects collisions between bounding boxes, which are perfect rectangles which encompass the entire clips.
The only way to create perfect collisions between objects without going through an in-depth math-based engine is to check one specific point with a full movie clip.

Example:
onClipEvent(enterFrame){
if(this.hitTest(_root._xmouse,_root._ymouse,true)){
trace("hit&quot
}
}

The function hitTest can be used in two ways:
mc1.hitTets(mc2)
or
mc1.hitTest(pointx,pointy,true)
The third parameter in the second method tells flash whether to use just the bounding box, or evaluate the exact shape of the clip, which only works if flash is working with a point rather than a second full movie clip.

Yeah, but remember that you can find loads of nice perfect hit test classes for free with google. For now, it's not fundamental that you understand how they work before using them.

@arobegamr

onClipEvent(enterFrame){
if(this.hitTest(_root._xmouse,_root._ymouse,true)){
trace("hit&quot
}
}

You mean in the example that: mouse is an object which you give the intance name: mouse?
and in the code you dont need "trace("hit&quot" right? You need to add the function there?

no, _xmouse e _ymouse are the two built-in flash variables for the mouse coordinates, but you can replace them with the coordinates of the point you want to hitTest.
and yes, you have to replace trace("hit&quot with all the stuff that you want to happen if the collision is happening.

but if a write "_xmouse" then which object will my hero hits?
can you write me the code: my character (which i move with tehe arrows) called hero, the object that my hero hits called wall? I would be really glad if you would do that for me.

Perfect hitTests cannot refer to a second movieclip, only a point. In the second example, _xmouse is not a clip, but a coordinate. By specifying _xmouse,_ymouse, you are telling flash to detect a collision with the mouse cursor.

It is, however, possible to check all corners of the hero's bounding box, while using the full second movie clip. For an example of how to do this, check out tonypa's tutorial: [url=http://www.tonypa.pri.ee/tbw/start.html]

(The tutorial covers much more than just that, and there is a lot more useful information)

Thanks now i get it, but still dont understand xmouse and ymouse.
BTW is this code ok:

onClipEvent(enterFrame){
if(this.hitTest(_root._x=200,_root._y=200,true)){
this._y-= 5;
}
}

?

Oseb: Your code isn't ok, what you're effectively doing is setting variables in your hittest coding - _root._x = 200. Depending on the outcome of setting this it will return either true or false I believe, but not any usable Number. Either remove the =200, or try getting your x and y values from somewhere else

I think I know what you're trying to do, Oseb, but if you want to detect collision between the object and the coordinate (200,200), then you need to remove the _root._x=

Just have this as you're code:
onClipEvent(enterFrame){
if(this.hitTest(200,200,true)){
this._y-=5
}

Thanks arobegamr!
But i have problem with the tird line: this._y-=5 if i add this then when my character reach the point he will be bounce back and if i hold the button then he will hit the wall perfectly, now i want to do the same. I mean don't dounce back just hit it.

onClipEvent(enterFrame){
if(this.hitTest(200,200,true)){
this._y-=5
}

Now i want this code with only y cordinate in. Then how is it writen?
Because i deleted the first 200 but then the second one became the firts one (its became from Y to X coordinate). I want that my char wont go under Y 200 (its like a floor).

onClipEvent(enterFrame){
if(this.hitTest(_root._x=200,_root._y=200,true)){
this._y-= 5;
}
}

onClipEvent(enterFrame) {

if(Math.sqrt((_x-_root.enemy_mc._x)^2 + (_y-_root.enemy_mc._y)^2) > (_width/2 + _root.enemy_mc._width/2)) {
//do this stuff if we overlap
}

}

I want that my blue circle stops on the black wall. If my wall intance name is wall and my character's is char. Then with this code how is it sounds like?

onClipEvent(enterFrame) {
if(Math.sqrt((_x-_root.wall_char._x)^2 + (_y-_root.wall_char._y)^2) > (_width/2 + _root.wall_char._width/2)) {
_root.char._y-= 5;
}
}

this?

Then with this code how is it sounds like?

onClipEvent(enterFrame) {
if(Math.sqrt((_x-_root.wall_char._x)^2 + (_y-_root.wall_char._y)^2) > (_width/2 + _root.wall_char._width/2)) {
_root.char._y-= 5;
}
}

this?

Here is the link of my image:

http://kepfeltoltes.hu/view/110530/ma_www.kepfeltoltes.hu_.jpg