# Bad FPS for smaller size (OpenGL ES with SDL)

If you saw my other question, well, there is still a little problem:

Basically, the frame rate is very bad on the actual device, where for some reason the animation is scaled (it looks like the left side on the video). It is quite fast on the simulator where it is not scaled (right side).

For a test, I submitted this new changeset that simply hard-codes the smaller size (in SDL_CreateWindow() and in glViewport()), and as you see in the video, now it is slow even in the simulator (left side shows the small size, right side shows the original size -- otherwise the code is the same).

I'm clueless why it's soooo slow with a smaller galaxy, in fact it should be FASTER.

The question is not about general speed optimization like reducing screen resolution or joining glBegin(GL_POINTS)/glEnd() blocks.

Update: For a test, I simply reduced the screen size to 320x480 and compiled it to OS X desktop -- got the same speed as with 800x800, so this size-specific slow-down is on iOS only. Will post this on the SDL mailing list now.

• The reason why it's faster on the simulator is due to the fact that the actual IOS simulator implementation has nothing to do with real IOS devices architecture, it's a software made to take advantage of your computers CPU and Graphics Card capabilities, which will always be faster than curren IOS devices. – Shivan Dragon Nov 19 '12 at 23:06
• thanks @shivan-dragon, but if you check out the youtube link I posted you will see speed difference of the two versions BOTH RUNNING ON THE SIMULATOR (and my question was: why is that? and why it's not happening on OS X, only on iOS?). I mentioned the real device only because SDL does an autoscaling there which I needed to manually do on the simulator for test purposes. – Gabor Nov 20 '12 at 8:35

• Thnx, I reduced both glPointSize and the number of stars in NBodyWnd and it's smooth enough now; and you definitely answered my question; of course it's not nearly as fast as the original youtu.be/AD9OV1Zrs4I but maybe that's just because my iPod cannot catch up with a Linux desktop – Gabor Feb 6 '13 at 14:22