edit Point?

[j pearce]

how can I change a Point variable without using new Point?
In the constructor I have this to establish the variable:

public var target:Point = new Point(0,0);

but in the looped function I want the target to equal mouseX,mouseY in real time i.e.

target.x = mouseX;
target.y = mouseY;

something like that (it must just change the existing point, not create a new one).
thanks

[matbury]

Hi j,

Yes, that's how you do it. See: http://help.adobe.com/en_US/FlashPla...ropertySummary

I hope this helps!

[j pearce]

Originally Posted by matbury

Hi j,

Yes, that's how you do it. See:

I hope this helps!

Hi thanks yeah that did help Think the reason it didn't work was that one of my other calculations was messing up. Basically what i'm doing is making an MC rotate to face the mouse and move towards it at a certain speed - works fine in AS2 but cant get it to work in AS3! Is there any difference between trig functions in AS2 & AS3?

Here's what I have:

package {
    import flash.display.*;
    import flash.events.*;
    import flash.geom.*;

    public class EnemySub extends MovieClip {
        public var target:Point = new Point(550,400);
        public var speed:Number = 20;
        public var xDiff:Number;
        public var yDiff:Number;
        public var hyp:Number;
        public var Angle1:Number;
        public var Angle2:Number;
        public var ShipSpeedMS:Number = 15;
        public var FinalShipSpeed:Number;
        public var DivisionFactor:Number = 30;
        public var hypDPS:Number;
        public var xDPS:Number;
        public var yDPS:Number;
        public var hypDPSPercentage:Number;
        public function EnemySub() {
            x = 200;
            y = 200;
        }
        public function EnemySubMove():void {
            //Target
            target.x = mouseX;
            target.y = mouseY;

            //Rotation
            xDiff = this.x - target.x;
            yDiff = this.y - target.y;
            hyp = Math.sqrt((xDiff * xDiff)+(yDiff * yDiff));
            Angle1 = (Math.atan2((target.y-this.y),(target.x-this.x)));
            Angle2 = Angle1*(180/Math.PI);
            this.graphic.rotation = Angle2;

            //ETA & Speed
            FinalShipSpeed = ShipSpeedMS/DivisionFactor;
            hypDPS = (FinalShipSpeed/hyp)*100;
            hypDPSPercentage = (FinalShipSpeed/hyp)*100;
            xDPS = ((xDiff/100)*hypDPSPercentage);
            yDPS = ((yDiff/100)*hypDPSPercentage);

            //Movement

            this.x -= xDPS;
            this.y -= yDPS;


        }
    }
}

Just seems to go where ever it likes because I think one of the trig functions is wrong... Any ideas anyone? BTW, if I just set the point coords it works fine, but by changing them whilst it moves to the mouse x & y it screws up...
Thanks.

[matbury]

Maths stays the same no matter what language you're using!

Check out the docs on Point again, there's some interesting functions for calculating distances, etc.

On your question, here's Keith Peter's approach (Copied and pasted from this book: http://www.apress.com/9781590597910). Arrow is a Sprite in the FLA library - you'll have to draw it yourself:

package {
    import flash.display.Sprite;
    import flash.events.Event;
    
    public class RotateToMouse extends Sprite {
        
        private var arrow:Arrow;
        
        public function RotateToMouse() {
            init();
        }
        
        private function init():void {
            arrow = new Arrow();
            addChild(arrow);
            arrow.x = stage.stageWidth / 2;
            arrow.y = stage.stageHeight / 2;
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
        
        public function onEnterFrame(event:Event):void {
            var dx:Number = mouseX - arrow.x;
            var dy:Number = mouseY - arrow.y;
            var radians:Number = Math.atan2(dy, dx);
            arrow.rotation = radians * 180 / Math.PI;
        }
    }
}

BTW, I love Keith Peter's book. It covers all the basics of dynamic 2D and 3D interactive animation and is project based so you get plenty of hands-on learning opportunities.

[j pearce]

Thanks mate I really appreciate this

[matbury]

You're welcome! Glad to help.