python 3.x - How to antialias when drawing to semitransparent frame buffers in OpenGL?

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65871130/how-to-antialias-when-drawing-to-semitransparent-frame-buffers-in-opengl

Answer 1

First of all, total_alpha isn't the sum of the alphas but rather the following:

total_alpha = 1 - (1 - source_alpha)*(1 - dest_alpha)

As you noted correctly, OpenGL doesn't support that final division by total_alpha. But it doesn't need to. All you need is to switch into thinking and working in terms of pre-multiplied alpha. With that the simple

glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

does the right thing.