GL_BLEND problem with drawing 2D sprites on iPad

Question

When we draw 300 sprites on the iPad using opengl 2.0 with glEnable (GL_BLEND) (which we need because the sprites need transparency and alpha blending), we get a frame rate of about 40. But when we turn off blending, we get a frame rate of 60 .

Is (alpha) mixing really expensive now or are we doing something wrong?

Thanks for your time, Richard.

Answer 1

The alpha mix is ​​really so expensive. The problem is that you can solve many problems with redundant code (which is very convenient for PowerVR) using Z-Buffering. It can save a ton of memory bandwidth by not writing to the Z-buffer and draw a buffer.

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Answer 2

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fragment * alpha + previous * (1 - alpha)

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