Getting a start touchPoint and end touchPoint to determine velocity AS3

Question

I'm trying to throw an object and create the angle and velocity the object is moving based on the beginning touch point and end touch point. So far I am able to track the touch points while dragging the object mySprite. I also have static gravity in place for when the object is released. However, I'm having a hard time figuring out how to link the two together.

I have a function onTouchEnd() that detects when the object is released and that's where the gravity kicks in. But right now nothing happens.

What am I missing to be able to pinpoint the start and end touch points and then save the angle between the two for the object's trajectory? Sorry for being such a noob.

EDIT: updated code using localX, localY

package  {
import flash.display.MovieClip;
import flash.events.*;
import flash.ui.Multitouch;
import flash.ui.MultitouchInputMode;
import flash.display.Sprite;

public class ThrowIt extends MovieClip{
    public var bg:Sprite = new Sprite();
    public var mySprite:Sprite = new Sprite(); 
    Multitouch.inputMode = MultitouchInputMode.TOUCH_POINT;
    public var startX:int;
    public var endX:int;
    public var startY:int;
    public var endY:int;
    public var angle:int;
    //public var speed:Number = 10; //this will change based on mouse speed
    public var moving:Number = 0;
    public var speedLimit:Number = 35;
    public var scale_x:Number = Math.cos(angle);
    public var scale_y:Number = Math.sin(angle);
    public var posY:Number = stage.y;
    public var goingUp:Boolean = false;
    public var goingDown:Boolean = false;
    //public var velocityX:Number = (speed*scale_x);
    //public var velocityY:Number = (speed*scale_y);

    public function ThrowIt() {
        mySprite.graphics.beginFill(0x336699); 
        mySprite.graphics.drawRect(0,0,40,40); 
        //addChild(bg);
        addChild(mySprite); 
        mySprite.addEventListener(TouchEvent.TOUCH_BEGIN, onTouchBegin); 
        mySprite.addEventListener(TouchEvent.TOUCH_END, onTouchEnd);
    }

    function onTouchBegin(e:TouchEvent) { 
        mySprite.startTouchDrag(e.touchPointID, false);

        /*TRACK THE START POINT OF THE DRAG HERE*/
        /*NEED THE X AND Y POSITION TO FIGURE OUT ANGLE AND VELOCITY OF OBJECT*/
        startX = e.localX;
        startY = e.localY;
        trace("the starting x is " + startX); 

    } 

    function onTouchEnd(e:TouchEvent) { 
        mySprite.stopTouchDrag(e.touchPointID); 
        /*TRACK THE END POINT OF THE DRAG HERE*/
        /*AGAIN, NEED BOTH THE X AND Y POSITION*/

        endY = e.localY;
        endX = e.localX;

        //angle = (endX - startX)*Math.PI(180);

        /*AFTER GETTING THE VELOCITY FIGURED OUT, THROW OBJECT*/
        if(!goingUp){
            goingUp = true;
            //moving = speedLimit*-1;
            moving = (startY - endY)*-1;
            moving += .2;
            mySprite.y += moving;
            mySprite.y = Math.min(mySprite.y, stage.stageHeight - 510); //min position of the object
            mySprite.y = Math.max(mySprite.y, 0); ///max position of the object
        }
        if(moving < 0){//if mySprite is still going up
            moving *= 1 - speedLimit/250;//decrease moving slightly
            if(moving > -speedLimit*.1){//if moving is small enough
                moving *= -1;//then begin to go down
            }
        }
        if(moving > 0 && moving <= speedLimit){//if mySprite is going down
            moving *= 1 + speedLimit/400;//increase the falling speed
        }
        mySprite.y += moving;
        //WHEN OBJECT GOES BELOW THE STAGE, DELETE IT AND STOP TRACKING EVENTS
        if(mySprite.y >= stage.stageHeight){
            removeChild(mySprite);
            mySprite.removeEventListener(TouchEvent.TOUCH_END, onTouchEnd);
            mySprite.removeEventListener(TouchEvent.TOUCH_BEGIN, onTouchBegin);

            trace("removed");
        }
    }


}

}

Answer 1

Calculating your angle using just x value seem strange, try this:

angle = Math.atan( (startY - endY) / (startX - endX) );  // in rad

This will give you the angle in radian.

For calculating the velocity you must have a timing variable between the start and the end touch. You can use getTimer() to get beginTime and endTime in your functions onTouchBegin and onTouchEnd respectively.

After that you just have to calculate velocity with distance and time.

distance = Math.sqrt( ((startX - endX)*(startX - endX)) / ((startY - endY)*(startY - endY)) );
velocity = distance / (endTime-beginTime); // in pixel/ms

Hope that helps ;)