Hi,
I am trying to make good 2D floating fog with particle system, and, of course it low my fps very good :). I want to ask, what is lowering framerate more - Size of particles or Emission?
Emission, of course. More emission = more geometrie
Neither unless you talk about 3GS only because iPad and iPhone4 will both take the fillrate hit from overdraw.
The large particles potentially hit less but optimally you have no particles at all but an image strip based animation representing the effect if possible, to get no overdraw at all, cause fillrate is the most precious resource kind of on the ipad and iphone4 as they have plenty of cpu and ram, but the same GPU as the 3GS, just with a much (4x iphone4, 5.2x ipad) larger amount of pixels to fill every frame
Large particles = kills fillrate. If you’re fillrate-limited, then you probably don’t care that much about some extra geometry if the CPU is not slow. So, there is no “of course” about it.
–Eric
The problem is small ones means more which also means more overdraw as every single particle shader uses blending and you need much more particles to get a comparable effect. they have the even larger fillrate impact normally due to the required masses.
Fillrate wise the only optimal solution is an image strip that holds the whole animation pre rendered already as that means only a single overdraw: that of the quad animating that strip.
it has the consequence of a larger memory footprint but the RAM side is far less a bottleneck than the fillrate on post-3GS