Texture Mask

author:
Daniel Sperl
description:
A mesh style that discards alpha values below a certain threshold; useful for masks.
compatible:
v2.0
tag:
mask, stencil, alpha
homepage:
https://gist.github.com/PrimaryFeather/d13b8d14d329a364c7cb

Overview

Starling 1.7 added support for stencil masks via a new property on display objects (“mask”). One way to create such a mask is to use the new “Canvas” class for drawing a vector shape.

However, for complex shapes, it's easier to simply use the pixels of a certain texture as a mask. That's what this class is for.

The Adobe Flash Plugin is needed to display this content.

Starling 2

The version for Starling 2 is implemented as a mesh style. This allows you to assign it to any mesh object (like Quad, Image, or even MovieClip). Any pixels with an alpha value below a certain threshold will be discarded. You can display such an object anywhere in the display tree, but it is especially useful as a stencil mask.

// get a sprite with some content
var sprite:Sprite = createMySprite();
addChild(sprite);
 
// create the image that will act as a mask, and assign the "TextureMaskStyle"
var mask:Image = new Image(assets.getTexture("shape"));
var style:TextureMaskStyle = new TextureMaskStyle();
mask.style = style;
sprite.mask = mask;
 
// change threshold to fine-tune the result
style.threshold = 0.3;

Starling 1.7

To use this extension with Starling 1.7, use the TextureMask class instead.

A “TextureMask” is actually a conventional display object, very similar to the “Image” class. The main difference to an image is that any pixels with an alpha value below a certain threshold will be discarded.

// get a sprite with some content
var sprite:Sprite = createMySprite();
addChild(sprite);
 
// create a "TextureMask" and assign it to the "mask" property
var textureMask:TextureMask = new TextureMask(assets.getTexture("shape"));
sprite.mask = textureMask;
 
// change threshold to fine-tune the result
textureMask.threshold = 0.3;

Changelog

  • 2015/05/07: First public version
  • 2016/02/18: Created Starling 2 version

User Comments

Feel free to edit this part of the page if you want to add information that's lacking in the above description.
Questions are better asked in the forum, though.

  extensions/texture_mask.txt · Last modified: 2018/04/04 11:43 by daniel
 
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