gles 2.0 perfomance on iphone simulator, iphone, macbook pro

Question

I did an wave animation to explore features of sgx chip which is tile-based rendering (TBR) architecture by comparing the performance on iphone and laptop. An advantage of TBR architecture is it allows the GPU to perform hidden surface removal before fragments are processed, so I draw many overlaped layers of animated waves, and only the wave in the top layer is visible. I did this program on both iphone 3gs (using gles 2.0) and my laptop, a macbook pro(using opengl 2.0). I recorded the fps numbers of different layers, and I assume trends of fps changes on iphone and laptop are different. I guess the performance's decreasing of iphone should be slower than on laptop, when the number of layers is increased. But they have very similar trends.

I have 2 questions. 1. why it doesn't show the advantage of TBR architecture, while there are alot of overlapped triangles 2. why the performance of iphone simulator is much much much much slower than just running on laptop(without simulator)? As documentations say the simulator does not enforce the memory limitations of MBX and SGX and take the advantage of laptop's CPU, i guess its performance should keep up with the laptop.

anyone can help? thanks alot

Answer 1

The OpenGL ES implementation in the iPhone Simulator is a software rasterizer and does not use the GPU in your MacBook.

What kind of framerate trends are you seeing, and in what way is only the wave on the top layer visible? Your primitives typically need to have framebuffer blending disabled and not issue discards in the fragment shader in order for hidden surface removal to skip fragment processing for what’s underneath.