I am doing some offscreen texture rendering. The offcreen rendering consists of a single rectangle, however it takes 1/3 to 1/2 of the total frame rendering time to draw this rectangle.
The current gl rendering target is one of GL_COLOR_ATTACHMENTn_EXT, and a pixel shader is active when the drawing happens.
What can I do to speed this up? Is GL_FRAMEBUFFER_EXT just that much slower than the onscreen rendering? Are there other factors I should investigate? Perhaps someone knows the best set of options for the texture attributes?
I am testing on a GeForce FX 5200, will a newer nVidia card perform better?