Hi and thanks for your replies! Note though that I want to get hold of the image/pixels after they have been processed by shader(s). So not the raw texture being fed in.
So maybe it would be the contents of a FBO or similar. Cheers Fred On Fri, Jan 15, 2021 at 3:59 AM Christian König < ckoenig.leichtzumer...@gmail.com> wrote: > Am 15.01.21 um 11:26 schrieb Michel Dänzer: > > On 2021-01-14 8:02 p.m., Blueroom wrote: > >> > >> Hi Everyone! > >> > >> I have a program that’s using dmabuf’s to create a zero copy > >> camera->GL texture pipeline and it’s working great on my RPi4. > >> > >> Now as a last step I want to access the pixels that Iv’e processed in > >> gl with shaders, on the cpu. > >> > >> Iv’e been told that on the Raspberry Pi OpenGL is sharing the same > >> memory as the cpu so I’m hoping it would be possible to do something > >> like a dmabuf on the ‘way out’ too? > >> > >> Does anyone have any pointers in how this could work? > > > > I'd recommend using glGetTexImage or other similar GL APIs for getting > > the data out of the GL texture. > > > > While mmap of a dma-buf file descriptor works in theory, direct CPU > > reads from GPU accessible memory can be very slow on some platforms. > > > > Yeah, agree. Additional to that you don't know the format of the DMA-buf > of the texture. > > The input image is most likely linear, but the output might be tiled. > > Christian. >
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