I'm trying to speed up particles, and one way to do that is by precomputing the texture rotations. What I want to do is load the texture, rotate it and save it to a handle.
How would I go about doing this?
Thanks in advance.
How does that save any significant amount of time? Presuming you handle the rotation in a vertex shader, that only saves time if you're VS bound.
If you are talking about a fixed-function pipeline, it's much cheaper to precompute the rotated edge vectors for the quads you are using. Rotating the texture is then done by the GPU. The only way that might incur additional cost is if you use a software renderer.
You can use a Framebufer Object (FBO) to draw the transformed texture into another texture, then you can use the generated texture and draw it to screen.