Is OpenGL threadsafe for multiple threads with distinct contexts?

Question

I know that sharing a single context between threads is bad news. I know that I can safely create and use a context with an offscreen framebuffer on a secondary thread when nothing is happening with GL on the main thread.

I haven't yet been able to find a definitive answer to the question of whether I can safely create two contexts on two different threads (say, a main thread drawing to the screen, and a secondary thread doing offscreen drawing work) and have them both making GL function calls simultaneously.

In other words, as long as the contexts are different, can two threads "share" the C API and thus the GPU? Or is that inherently something that is unshareable? Or is this implementation-specific?

Asking specifically for OpenGL ES on iOS, but it's probably a general GL question.

Thanks.

Answer 1

Yes, you need to use one context for each thread you want to use OpenGL with, also you can share objects between the contexts. This is the way to go :)