Re: [PyOpenGL-Users] glReadPixels not working in thread

[Shir G. <shi...@gm...>]

Thanks a lot!

Actually my goal is to generate data for learning in parallel to the actual
learning process.
So I thought of doing so in another thread.
On Tue, 23 Jan 2018 at 23:10 Ian Mallett <ia...@ge...> wrote:

> ​It's not entirely clear to me your setup. It looks like you're trying to
> use a subprocess? A few things:
>
> - Threads in Python add parallelism, but not performance, due to the
> global interpreter lock. They may even be pure software threads.
> - OpenGL contexts are not threadsafe. It is usually considered an error to
> use OpenGL from multiple threads, although in-principle it can be done if
> the parallel executions correspond to a serial execution, with no overlaps
> (through, e.g., tons of mutexes).
> - Subprocesses definitely will suffer at least that problem. IDR exactly,
> but it may be an error to attempt to share a GL context across
> subprocesses, regardless of any synchronization.
>
> Recommendation: keep all GL calls in one thread, and don't use threads in
> Python anyway unless you need asynchronous operations. If profiling shows
> that OpenGL *command overhead* really is the bottleneck *and* this is
> worth investing effort fixing, move to C++. If you still don't have enough
> performance, move from OpenGL to Vulkan (which unlike GL will allow you to
> build and issue command lists in parallel).
>
> Ian
>