rotation angle and spawn point of laser beam in flash game - actionscript-3

Question

I am trying to figure out the rotation angle and generation point of a laser beam that shoots up from a Cannon on Mouse Click. I am using ActionScript 3 and Flash for the same.
I rotate the beam based on my mouse cursor position which I feel works just fine. The
The issue is the generation point of my laser beam and it goes out of order. I want it to snap to the cannon ie its rotation point has to be the cannon. How do I do this in Flash?
Please have a look at the image file to get so that I am more clear.
Here is the code snippet that does the rotation and position logic in actionscript
laserBeamRight = new RightLaserBeam();
stage.addChild(laserBeamRight);
laserBeamRight.x = 812.65;
laserBeamRight.y = 400.1;
var angle2:Number = Math.atan2(stage.mouseY - laserBeamRight.y, stage.mouseX - laserBeamRight.x);
laserBeamRight.rotation = 180 * angle2/Math.PI;
I have hardcoded values for the position. They represent the right cannons position in the stage.
Here is the image file that shows the problem.
So I want the beam is targeting the mouse crosshair which is fine but I want it to be fixed and rotated around the cannon.
Another image with two beams at different angles. X position is right but Y position looks out of place because of the angle
One last image which clearly shows my problem.
The X position is right so is the Y position but it is originating from the center point of the beam and not the end point or the tail of the beam. I want the tail of the beam to be snapped to the cannons position. I tried changing the pivot point of the beam movie clip inside flash to the tail but that did not help.
Any idea?

Answer 1

First of all, adjust laser MC so that its anchor point is at its beginning instead of the middle, then align it to the turret's center as you do already. Then, when you are about to hit an object at specific (x,y), calculate rotation using Math.atan2() for the translated coordinates of mouse cursor (employ turret.globalToLocal(new Point(event.stageX,event.stageY)), then you should scale the laser so its end will hit the cursor position, change its scaleX. Note that you should do all transitions in one coordinate space (turret's), you apparently turn the turret's cannon part already, so you can do the same for your laser, and add it as part of a turret, probably positioning it behind the cannon part. An example:
// laser MC is like this: *>>>>>>>-------
// * is anchr point, laser is aligned righwards
const laserlength:Number=500; // the length of the laser, the X of the point you want to hit the cursor
....
function fireLaser(e:MouseEvent):void {
// creates a laser
var laser:Laser=new Laser();
laser.x=turret.centerX; // where to position the laser beginning
laser.y=turret.centerY; // relative to the turret
turret.addChildAt(laser,0); // add as a part of turret, behind everything
var cursor:Point=turret.globalToLocal(new Point(e.stageX,e.stageY));
laser.rotation=Math.atan2(cursor.y-laser.y,cursor.x-laser.x)*180/Math.PI;
// rad-to-deg conversion
laser.scaleX=Point.distance(cursor,new Point(turret.centerX,turret.centerY))/laserlength;
// lasers.push(laser); // expecting you to do this so laser should fade with time
}