Hello everybody!
Here is a new example of
animation created with Flash CS3 and Actionscript 3.0 .
In this case, I simulate the trail of an object in movement.
As always I underline the fact that this example is purely didactic (not to say that my graphics can be ugly) and therefore once learned the logic and the techniques of the code, it will be up to you to personalize the SWF to your liking with the better graphics.
Free your fantasy and let it take over the control...
This is the final result:
I create a FLA and I save it as "main.fla".
Into which, I have a MovieClip in library named "mc_clip" to which I associate the class named Clip (let Flash create it for you).
I create the Document Class, an AS file saved as "Main.as", implemented the following way:
Code:
package
{
import flash.display.MovieClip;
import flash.events.Event;
public class Main extends MovieClip
{
private var clip_mc:MovieClip;
private const RADIUS:int=120;
private const FRICTION:Number=.95;
public function Main()
{
init();
}
private function init():void
{
stage.frameRate=31;
createClip();
}
private function createClip():void
{
clip_mc=new Clip();
clip_mc.x=stage.stageWidth/2+Math.cos(clip_mc.angle*2)*RADIUS;
clip_mc.y=stage.stageHeight/2+Math.sin(clip_mc.angle*3)*RADIUS;
clip_mc.angle=0;
addChild(clip_mc);
clip_mc.addEventListener(Event.ENTER_FRAME,go);
}
private function go(evt:Event):void
{
evt.target.x=stage.stageWidth/2+Math.cos(clip_mc.angle*2)*RADIUS;
evt.target.y=stage.stageHeight/2+Math.sin(clip_mc.angle*3)*RADIUS;
evt.target.angle+=.05;
var copy_mc:MovieClip=new Clip();
addChild(copy_mc);
copy_mc.x=evt.target.x;
copy_mc.y=evt.target.y;
copy_mc.addEventListener(Event.ENTER_FRAME,goCopy);
}
private function goCopy(evt:Event):void
{
evt.target.alpha*=FRICTION;
evt.target.scaleY=evt.target.alpha;
if(evt.target.alpha<=.3)
{
evt.target.removeEventListener(Event.ENTER_FRAME,goCopy);
var m:MovieClip=evt.target as MovieClip;
removeChild(m);
}
}
}
}
Let us analyse the code
Properties
a variable of type MovieClip which will instance the class Clip associated to the MovieClip "mc_clip" placed in the FLA"s library
private var clip_mc:MovieClip;
a constant containing the radius value of the angle used to move the MovieClip
private const RADIUS:int=120;
a constant used as friction ( see
this tutorial )
private const FRICTION:Number=.95;
Constructor function
I call the method init
init();
Methods
init();
I impost the frame rate
stage.frameRate=31;
I call the method createClip
createClip();
createClip();
I create a new Clip
clip_mc=new Clip();
I impost the x and y using sinus and co sinus. To start the animation, I will use the same logic of sinus and co sinus so the clip will already have the initial coordinates and when I attach the clip, no scat will be seen.
clip_mc.x=stage.stageWidth/2+Math.cos(clip_mc.angle*2)*RADIUS;
clip_mc.y=stage.stageHeight/2+Math.sin(clip_mc.angle*3)*RADIUS;
I add a property to clip_mc named "angle" and I impost it to zero
clip_mc.angle=0;
I add clip_mc to the stage
addChild(clip_mc);
I add ENTER_FRAME to clip_mc which will call the method go as many times by seconds based on the frame rate (in this case, the method go will be called 31 times)
clip_mc.addEventListener(Event.ENTER_FRAME,go);
go(evt:Event):void
I assign x and y to clip_mc based on the values obtained on simple
trigonometry
evt.target.x=stage.stageWidth/2+Math.cos(clip_mc.angle*2)*RADIUS;
evt.target.y=stage.stageHeight/2+Math.sin(clip_mc.angle*3)*RADIUS;
I increase the property angle of clip_mc
evt.target.angle+=.05;
I create another Clip named copy_mc
var copy_mc:MovieClip=new Clip();
I add it to the stage
addChild(copy_mc);
I assign the same coordinate x and y of clip_mc to copy_mc
copy_mc.x=evt.target.x;
copy_mc.y=evt.target.y;
copy_mc will have its own ENTER_FRAME which will call the method goCopy
copy_mc.addEventListener(Event.ENTER_FRAME,goCopy) ;
goCopy(evt:Event):void
I apply the friction to the property alpha of copy_mc
evt.target.alpha*=FRICTION;
I impost the property scelY of copy_mc with a value equal to its alpha
evt.target.scaleY=evt.target.alpha;
I check if the alpha of copy_mc is lesser then 0.3
if(evt.target.alpha<=.3)
{
If it is, I stop the ENTER_FRAME of copy_mc
evt.target.removeEventListener(Event.ENTER_FRAME,g oCopy);
I remove copy_mc
var m:MovieClip=evt.target as MovieClip;
removeChild(m);
}
See you soon!
15-11-07, 06:51
Re: Trail effect
Re: Trail effect
Re: Trail effect
Linear Mode
