Shader: blend multiple textures with alpha logic

hi all,

I want to have layers of textures with alpha overlaying each other.
Could you tell me the logic on how to process the rgba data within the pixel shader? I got stuck here.


could you be more precise ?
you want a master alpha coeff which controls every blending of each layer ?


I want multiple textures rgba on top of each other. no color manipulation, just calculate all visible pixels, according to the masks, with their original color.
like a spreaded filetexture.