Alpha value in shaders

[GBagley]

Hi,

 

I'm starting to play with shaders (AbstractFilter) in PIXI, but have gotten stuck trying to use the alpha value. It seems that in the vertex shader the attribute aColor.a (the alpha) is always at 1.0, even though in pixi I'm specifying that the alpha on the graphics object is lower. Which alpha value from pixi is being passed to the shader? Example here:

 

http://jsfiddle.net/tLc5c8yd/

 

In this, one box has an alpha of 0.6 and the other has an alpha of 1.0. In the vertex shader, I'm trying to change the emitted color of the vertex based on the alpha (>= 1.0 is red, < 1 is green) but they both come up the same color.

[xerver]

I think there is a misunderstanding, aColor is for "colorizing" or tinting an object. Your tint is white (by default) so you get vec4(1.0, 1.0, 1.0, 1.0).

aColor is not the color of the object you are drawing it is the tint you are applying (and in some eccentric features can be used for premultiplied alphas).

[GBagley]

I think there is a misunderstanding, aColor is for "colorizing" or tinting an object. Your tint is white (by default) so you get vec4(1.0, 1.0, 1.0, 1.0).

 

 

Oh! I see. I grabbed the default TextureShader sources for some reason... Guessing I want the one of the primitive ones for Graphics objects instead. Could you describe the difference between the default  PrimitiveShader and the ComplexPrimitiveShader, and when pixi uses each? Looks like the difference has something to do with coloring/blending -- complex using a uniform for color rather than an attribute?. 

 

Thanks

[GBagley]

Nevermind. Reading through the source. Looks like ComplexPrimitiveShader is just for complex polygons (mode === 1). All other primitives (mode === 0) use the PrimitiveShader.