dynamic-gradient mask acts like rectangle

[pet-theory]

Hi:

I'm trying to:

1) draw a gradient with code
2) use it as a mask on a bitmap

the masked bitmap is embedded and instantiated: new EmbeddedClass()
the mask is created via a new Shape()
that Shape uses the graphics object methods to draw it: beginGradientFill, draw Rect, etc.
the gradient has an alphas array like this: [0, 255], so it goes from visible to invisible (I've checked this)
the actual masking: maskedBitmap.mask=maskShape;

the result is a solid mask, not a gradient mask...how can I apply a dynamic gradient mask?

the code is not pretty but here it goes:

package {
	import flash.display.Bitmap;
	import flash.display.BitmapData;
	import flash.display.BitmapDataChannel;
	import flash.display.DisplayObject;
	import flash.display.InterpolationMethod;
	import flash.display.Shape;
	import flash.display.SpreadMethod;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.filters.DisplacementMapFilter;
	import flash.geom.Matrix;
	import flash.geom.Point;

	public class TestIt extends Sprite
	{
		[Embed(source="images/desert.jpg")] internal var Desert:Class;
		internal var picture:Bitmap;
		internal var rippleMap:BitmapData
		internal var rippleFilter:DisplacementMapFilter;
		internal var offset:Point;
		internal var bandMask:Shape;
		internal var bgPicture:Bitmap;
		public function TestIt()
		{
		//put embedded picture in a bitmap
		picture= new Desert();
		//clone a background for when the foreground picture is partly masked
		bgPicture=new Bitmap(picture.bitmapData.clone());
		addChild(bgPicture);
		addChild(picture);
		//create a displacement map based on blue, with a lot of noise along y
		rippleMap=new BitmapData(picture.width, picture.height/2);
		rippleFilter=new DisplacementMapFilter(rippleMap, new Point(0,50), 100, BitmapDataChannel.BLUE, 0, 55, "clamp", 0, 0);
		//listen to enterframe and animate the filter by continously offsetting the filter's displacement map's perlin noise
		addEventListener(Event.ENTER_FRAME, makeRipple) 
		offset=new Point(0,0);
		//create a gradient to use as a mask
		bandMask=new Shape();
		var colors:Array=[0xffffff, 0x0000FF];
        var alphas:Array=[100,0];
        var ratios:Array=[0, 255];
        var spread:String=SpreadMethod.PAD;
        var inter:String=InterpolationMethod.LINEAR_RGB;
        var focal:int=0
        var mat:Matrix=new Matrix();
        mat.createGradientBox(640, 200, -Math.PI/2);
  	    bandMask.graphics.beginGradientFill("linear",colors,alphas,ratios,mat, spread, inter, focal);
		bandMask.graphics.drawRect(0, 50, 640,200)
		bandMask.graphics.endFill();
		bandMask.blendMode="layer"
		//put the mask on the display list and mask the picture
		addChild (bandMask);
		picture.mask=bandMask;
		}
		
		internal function makeRipple(evt:Event):void {
			//move the first octave of the perlin noise
			offset.x+=.2;
			offset.y+=.6;
			rippleMap.perlinNoise(150,20, 5, 89, true, true, BitmapDataChannel.BLUE, false, [offset]);
			picture.filters=[rippleFilter];
		}
		}
	
	}

basically, I'm using the DisplacementMapFilter to make heat rise from the horizon in the desert, but I'd like the ripples to fade out gradually into the sky by using a gradient mask

I'm considering alternatives, like merging the gradient right onto the displacement map (to fade the perlin noise gradually wherever I want)

that would probably be easier on the processer, less alphaing, but still, I'd like to know how to get a dynamic gradient mask working

[csdstudio]

Unless they've changed the mask behavior, masks have always been just on or off. Nothing in between, just based on the shape of the mask, not its color or alpha values.

[pet-theory]

...so I doubt that AS3 will turn back the clock

but I never actually drew a gradient dynamically in Flash 8, so I don't know if that is possible in 8 or AS3

perhaps in both it is only possible with a gradient created in the IDE, so we have to wait for Blaze? I hope not.

[Incrue]

Originally Posted by csdstudio

Unless they've changed the mask behavior, masks have always
been just on or off. Nothing in between, just based on the shape of the mask, not its color or alpha values.

And this is what?
http://www.gotoandlearn.com/ (click in Creating alpha masks)

[Tink]

you can create gradient masks by using a BitmapData as the mask (might be Bitmap in AS 3.0).

[senocular]

For AS2 you'd have to use cacheAsBitmap - Id suspect the same might be true for AS3, but I have yet to try it so I am not sure.

[pet-theory]

I turned the shape mask into a bitmap, as per Tink, but it still does not work.

Then after a little experimentation, I found that even a normal fill with alpha set to zero acts as a mask. Hm.

So maybe this has nothing to do with gradients:

shapeMask=new Shape();
 shapeMask.graphics.beginFill(0xFFFFFF, 0);
shapeMask.graphics.drawRect(0, 0, 640,200)
shapeMask.graphics.endFill();
bitmapDataMask=new BitmapData(640, 200,true, 0xFFFFFFF)
bitmapDataMask.draw(shapeMask);
bitmapMask=new Bitmap(bitmapDataMask);
//put the mask on the display list and mask the picture
addChild (bitmapMask);
picture.mask=bitmapMask;

A rectangular mask is applied, even though the alpha is zero.

[csdstudio]

Originally Posted by Incrue

And this is what?
http://www.gotoandlearn.com/ (click in Creating alpha masks)

Like I said, unless they've changed it! That is really cool. I stand corrected.

[gburks]

This was the tutorial that taught me how to do it (its been available since Flash 8's cacheAsBitmap):

http://www.devx.com/webdev/Article/29296/1954?pf=true

Basically, it says that you need to use ActionScript rather than the designer interface to tell your gradient that it is the mask. Instead of right clicking your mask layer and making it a mask there, use code like this:

maskee.cacheAsBitmap = true;
maskMC.cacheAsBitmap = true;
maskee.setMask("maskMC");

.. it will cache both the mask and the maskee as a bitmap and make the gradient layer gradually unmask the maskee layer, rather than showing its entire rectangle.

[Incrue]

Originally Posted by csdstudio

Like I said, unless they've changed it! That is really cool. I stand corrected.

You sayd

masks have -- always -- been just on or off.

Its not -always- cos f8 has changed it from a long time, Bitmapdata masks are not an AS3 new object.
Pet theory was asking how to do in AS3 some old f8 stuff