I have these particles drawn with transparency, and as such have turned off writing to the depth buffer. They are waterfalls that start blue and turn white as they hit bottom and lose energy. Unfortunately, this creates noticeable z fighting that is really bugging me, since the flickering seems to happen in unison with all the other waterfalls on screen.
I don't suppose there is a way to turn on the depth buffer only for pixels at full alpha? I'm not even sure that would look better as the sprite edges would still fight... What if anything can be done about this? Sorting them seems out of the question since there's hundreds of thousands of them. They are sorted by age I suppose, maybe I can use a depth bias.