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Re: [Public WebGL] Premultiplied alpha blending and issues with color accuracy

You usually do that with 2 textures and it works like this:
a = your current drawing
b = the current render target attached to an FBO

1. copy a to b by way of screen quad copy sourcing from a
2. draw what you want to add, sourcing from a and from whatever source
you need to draw, using your custom blending equation, still outputting to b
3. swap a and b

This would work in the case of an image calculated in the shader, I suppose, so that's a possible solution for the brush issue, but what about blending 2 textures together? I suppose that if I'm going to implement layers, I could just blend these to the main frame buffer by using premultiplied alpha, since I'm not actually outputting an alpha channel to the 3D canvas. For a low number of layers with relatively high opacity values, this should look fine, I guess.


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