Why no glGetTexSubImage() ??

I want to read the colour of a single texel in a large GL texture (for diagnostic purposes).

Do I /really/ have to either use glGetTexImage() to copy the /entire/ texture into CPU RAM ;
or render a portion into the frame buffer and use glReadPixels() hoping the render preserved the colour?

Both approaches suck bigtime when all I want to do is peek particular single texel cells. glGetTexSubImage() would do what I want if it existed but it doesn’t seem to be implimented.

Can anybody help? TIA.

Attach the texture to an FBO. When the FBO is bound you can ReadPixels from it.

OK thanks. Can you direct me to suitable online DOCs for FBO s?

The specification provides some examples and is well-suited as a tutorial