[sounds]

Intel has a great set of papers; the idea is to store a few of the semi-transparent pixels in a texture, then overflow to a storage buffer as needed.

https://www.gdcvault.com/play/1014547/Adaptive-Order-Indepen...

Especially at around 15:06 they make a great argument that above a certain limit, the net effect of additional pixels is minimal (because they will be blended behind a significant fraction of the whole picture, so just mushing together a few semi-transparent pixels at the _back_ of the stack is reasonable).

The problem is getting each pixel's data as small as possible so the texture doesn't overflow the limits of texture sizes in GPUs - typically mobile devices have a limit of 128 bits per pixel in texture sizes. Also, mobile devices don't really have enough GPU RAM to do this kind of order independent transparency on the 4x anti-aliased framebuffer.

After solving the above problems you're ready to spill some pixels into the storage buffer (again, because most pixels on the screen don't have 8 semi-transparent pixels in them, so spilling to overflow for the few ones that do may be faster than trying to keep it all in the texture). Now you're ready to do something like this technique.