Using glReadPixels and glDrawPixels

Hi all, I’m new to OpenGL and learning fast :wink:

I have a section on my screen that take allot of CPU to create.
I would like to just calculate the drawing once and just reuse it.
If i have to recalculate the drawing every time I render, it can max out the cpu.

I’ve been looking into glReadPixel and glDrawPixel.
I would like to grab a rectangle off the screen after the screen is drawn and just glDrawPixel it any time I want to render new objects on top of it.

However I’m having no success and have not been able to find any examples on Google. any help is appreciated.

Instead of glRead/draw pixels Youre better off creating a texture the same size as u want
and then using
glCopyTexSubImage2d(…) to copy from the screen into the texture + then drawing the texture to the screen subsequently.

The reason being is drawing textures is faster/less CPU intensive than drawing pixels