[Interest] Sporadic rendering problem QtQuick/OpenGl

[Sean Harmer]

Hi,

On 19/10/2016 22:22, Patrick.Flaig at continental-corporation.com wrote:
> Hi,
>
> I got the recommodation to send my question/problem to this mailing list.
>
> On our i.MX6 based target device we can observe sporadic rendering
> problems when using QtQuick.
> As the problem is only happening sporadic we were not able to create a
> specific code that is causing the rendering problem.
>
> Background information: our system has two framebuffers, Qt is rendering
> in the foreground framebuffer.
> We are using Qt 5.6 running on a Linux Kernel 3.10.17 (patches from NXP
> for the iMX6 are applied), including latest opengl libraries from NXP.
>
> We have seen two issues:
> 1.        Triangle showing parts of the background framebuffer._
> _<https://s10.postimg.org/vdi5l8dl1/issue_1.jpg>
> 2.        Warped Graphics_
> _<https://s10.postimg.org/n9a1ghr5x/issue_2.jpg>
>
> We have already started a discussion with NXP regarding that issue.
> The last statement from NXP is:
> 1.        Eventually I suspect here an error in the QT framework when
> passing the mesh to OpenGL. It can be that for example a very simple
> geometry is used in the vertex buffer (e.g. 2 triangles defining the
> full frame buffer) but in the end 3 or more triangles are specified due
> to an application software error, so the OpenGL pipeline tries to render
> a 3rd triangle. For that it reads the coordinates from the vertex buffer
> (that contains valid data only for 2 triangles !), and thus invalid data
> is read therefore random triangles appear on the screen.
> 2.        In this example again it looks like a geometry problem.
> Because the texture containing the gauge appears to be mapped on a
> strange 2d mesh composed by two incomplete circles. My idea with alpha
> was just to confirm that some draw primitives are corrupted, which is
> pretty clear now.
>
> Does anybody know about existing Qt bugs which could cause the issue we
> can observe?
> Any ideas how to debug this issue?

Try using the Qt Quick 2 geometry inspection tool in gammaray.

Cheers,

Sean

>
> Thanks a lot.
>
> Patrick
>
> http://www.continental-corporation.com
>
>
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-- 
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
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