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glReadPixels

Sebastien (OBSOLETE) Baudouin
Note: This was originally posted on 9th March 2012 at http://forums.arm.com

Hi all,

i try to render scene in an off screen  way, controlling the location of my pixels (the pointer is fixed by myself).
It seems that MALI400 is not supporting eglCreatePixmapSurface, interface that would allows me to create a  surface that will use pixels in the location i want.

As it is not working i have to use the API glReadPixels which is very very slow (compare to other GPU).

So i'm wondering if there is a reason for such bad perf for ReadPixels and if someone knows a way with MALI to render a scene at place (pixel buffer address) you want.

Thanks for your help.

BR

Seb
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  • Note: This was originally posted on 10th March 2012 at http://forums.arm.com

    Hi Seb,

       I am sorry that you are facing problems with pixmap surfaces. Could you let us know what errors you get when trying to use pixmap surfaces. After every EGL call , you can check if an error has been generated using eglGetError.  Could you let me know what error it shows? It might also help us if you can share snippets of code where the pixmap surface is created.

    Also, with respect to glReadPixels, we generally advise programmers not to use that particular API call as it is causes a flush and breaks the rendering pileline. This will cause huge performance impacts.

    BR,
    Karthik
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  • Note: This was originally posted on 10th March 2012 at http://forums.arm.com

    Hi Seb,

       I am sorry that you are facing problems with pixmap surfaces. Could you let us know what errors you get when trying to use pixmap surfaces. After every EGL call , you can check if an error has been generated using eglGetError.  Could you let me know what error it shows? It might also help us if you can share snippets of code where the pixmap surface is created.

    Also, with respect to glReadPixels, we generally advise programmers not to use that particular API call as it is causes a flush and breaks the rendering pileline. This will cause huge performance impacts.

    BR,
    Karthik
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