How to change MovieClip transparency based on mouse position? - actionscript-3

Question

So, I'm trying to make a grid of rectangles each get more transparent the closer the mouse is to it.
Using some basic maths, I thought I had got it, but instead it seems I got a weird graphic bug(maybe?) shown here:
The middle of the rings is where the mouse is.
Part of code that deals with transparency:
private function update(e:Event = null):void
{
for (var i:int = 0; i < buttons.length; i++) {
lightFact = getDistance(buttons[i])
lightBrightness = lightPower - (lightFact * 10)
buttons[i].alpha = lightBrightness
}
}
getDistance is just getting distance from the block to the mouse.
Each rectangle is a movie clip, if that matters.

Answer 1

If you are trying to do this:
Then I think your problem is basically that your alpha value is ranging from 0 to about 3000 or something like that. That's going to cause strange effects. The value needs to range smoothly from 0 to 1 (so it needs to be a floating point number as in Number).
Here is the code which generated the image above which I wrote for you that will get you started in the right direction:
package
{
import flash.display.*;
import flash.events.*;
public class lightFactTest extends MovieClip
{
private var boxesArray: Array = new Array();
private var xDist: Number = 0;
private var yDist: Number = 0;
private var d: Number = 0;
private var size_Glow : Number = 0;
private var size_Radius : Number = 0;
public function lightFactTest(): void
{
// creates a background for rectangles array.
var BG_box: Sprite = new Sprite();
BG_box.graphics.lineStyle();
BG_box.graphics.beginFill(0x080839);
BG_box.graphics.drawRect(0, 0, stage.stageWidth, stage.stageHeight);
BG_box.graphics.endFill();
addChild(BG_box);
//# creates a grid of sprites (rectangles).
for (var i:int = 0; i < (stage.stageWidth / 10); i++)
{
for (var j:int = 0; j < (stage.stageHeight / 10); j++)
{
var box: Sprite = new Sprite();
box.graphics.lineStyle();
box.graphics.beginFill(0xFFFFFF);
box.graphics.drawRect(0, 0, 10, 10);
box.graphics.endFill();
addChild(box);
box.x += i*10; //+ 50;
box.y += j*10; //+ 50;
boxesArray.push(box);
}
}
addEventListener(Event.ENTER_FRAME, lightCalc);
}
private function lightCalc(e: Event): void
{
size_Glow = 3.5;
size_Radius = 0.64;
//# iterates through the array calculating each distance and then alpha.
for (var i:int = 0; i < boxesArray.length; i++)
{
xDist = Math.abs(stage.mouseX - boxesArray[i].x);
yDist = Math.abs(stage.mouseY - boxesArray[i].y);
//var d: Number = Math.pow(xDist * xDist + yDist * yDist, 0.5);
d = Math.sqrt(xDist * xDist + yDist * yDist) / (size_Radius / 5);
//# This is the code that you really need to focus on...
boxesArray[i].alpha = Math.min(1 / d * 10, 1 ) * (Math.PI / 0.5 - Math.min(size_Radius, 0) ) * size_Glow;
}
}
}
}
Hope that helps!