[AS3] Calculating angle for shooting bullets

[bastrix]

Hi all,

This is what im trying to do:

I have a character in middle of the screen that I can move around. The idea is that I can aim with the mouse, so wherever the mouse is pointing the character will shot a bullet in that direction until its out of the screen.

I've done the maths before where I had the rotation and I could calculate how to move an object depending on the actual rotation value. But how would I do this if I only have the Cords of my character and the mouseX and mouseY cords of where I just clicked?

Any idea?

Thanks

[hey]

Something like this:

dx = object.x - mouseX;
dy = object.y - mouseY;
Radians = Math.atan2(dy, dx);

Then you can have the projectile move with something like:

Projectile.x += Math.cos(Radians) * 5;
Projectile.y += Math.sin(Radians) * 5;

[lordofduct]

trig yo...


The specific function you want is ArcTangent, and there is a nice arctan that solves the repeating aspect of it (because top and bottom can resolve the same)


Math.atan2(j, i)

where j and i are the members of the vector <i,j> pointing from the player to the mouse.

j = mouseY - player.y
i = mouseX - player.x

[bastrix]

Thats what I needed... thanks! I think I'm gonna have go through a few trigonometry tutorials ...

[northmantif]

var speed:Number = 10;
var bull:MovieClip;//represents bullet dynamically adding from library;
var bulletAngle;
addEventListener(Event.ENTER_FRAME, moving);

function moving(e:Event):void 
{
        mc.rotation = Math.atan2( mc.y -  mouseY,  mc.x - mouseX) / Math.PI * 180 -90;
        //mc represents something that should fire the bullet (cannon, soldier etc.)
        //and in my case it is a movieClip placed manually on stage 
}
stage.addEventListener(MouseEvent.CLICK, shot);

function shot(e:MouseEvent):void 
{  
        bull = new Bullet();    //new instance of Bullet        
        addChild(bull);

        bull.x = mc.x
        bull.y = mc.y;
        bull.rotation = (mc.rotation -90)* Math.PI/180;
        bulletAngle = bull.rotation ;
        bull.addEventListener(Event.ENTER_FRAME, movingBull);
}

function movingBull(e:Event):void 
{
    e.target.x += Math.cos(bulletAngle)*speed;
    e.target.y += Math.sin(bulletAngle)*speed;
}

that's what I use