frame capturing of transform feedback simulation

Hi all,
I recently tried to grab frames from my realtime mass spring sim. application. The application uses double buffered vbos and texture buffer objects with transform feedback to update the vbos and its pretty fast i get over 1000 fps. Now when i am grabbing frames using fraps or anyother grabber, the frame rate drops to 100 fps which is very slow. It affects my simulation speed which drops considerably. What may be causing this?


Fraps probably blocks swapbuffers as long as needed to completely retrieve the rendering and store it on disk. For high resolution, it is not surprising it takes time.
If speed is independant from resolution, then maybe Fraps adds a vsync.
You can try to do your own grabber, integrated with an async PBO to let current rendering happen on other buffer on GPU, while you retrieve previous render in parallel on the CPU.

Thanks for the input Zbuffer.