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Qt QML Scene Graph trouble with EGLFS

evgeny grebenev
Prodigy 60 points
Other Parts Discussed in Thread: AM3517

Hello all!
I develop a medical application for embeded system (with eglfs, AM3517 processor based). I need to create a QML scene containing raw OpenGL Item (for displaying real-time graph).
I found this example in Qt documentation: http://qt-project.org/doc/qt-5.1/qtquick/scenegraph-textureinsgnode.html
, and modify it for my application (Change TextureNode class for render some VBO into FBO ).
I also have many other QML files that contain various elements of the interface.

So.. then i run application with only openGL Item, i have 10% CPU usage:
main.qml

  1. import QtQuick 2.0
  2. import Graphics 1.0
  3. Rectangle {
  4.     width: 800
  5.     height: 600
  6.     color: "Gray"
  7.     GraphItem{
  8.         x: 230; y: 180
  9.         width: 210
  10.         height: 160
  11.     }
  12. }

Then i run application with openGL Item and more other QML elements, do not overlap OpenGL item, i have 50% CPU usage!!:
main.qml

  1. import QtQuick 2.0
  2. import Graphics 1.0
  3. Rectangle {
  4.     width: 800
  5.     height: 600
  6.     color: "Gray"
  7.     GraphItem{
  8.         x: 230; y: 180
  9.         width: 210
  10.         height: 160
  11.     }
  12.     MyOtherItems{
  13.    // this contains many rectangles, texts and other
  14. }
  15. }


I conclude that Scene Graph Renderer render All items every time.

But i need render only OpenGL Item!

I found, that Qt Scene graph include alchoritm for partial scene update (qt-project.org/doc/qt-5.1/qtquick/qtquick-visualcanvas-scenegraph.html). Why this alghoritm not working for me?

My SGX driver version is 4.06.00.02.

My Qt version is 5.0.

My extra enviroment variables:
 TSLIB_FBDEVICE=/dev/fb0   
 TSLIB_TSDEVICE=/dev/input/event1
 TSLIB_CONFFILE=/etc/ts.conf
 TSLIB_CALIBFILE=/etc/pointercal
 TSLIB_CONSOLEDEVICE=none
 QWS_MOUSE_PROTO=Tslib:/dev/input/touchscreen0
 QT_QPA_EGLFS_WIDTH=800
 QT_QPA_EGLFS_HEIGHT=600
 QT_QPA_EGLFS_HIDECURSOR=1
 QML_RENDER_TIMING=23

My /etc/powervr.ini file is:

[default]
WindowSystem=libpvrPVR2D_FRONTWSEGL.so
ParamBufferSize=33554432

Application output:

evdevtouch: Using device /dev/input/event1
min X: 0 max X: 0
min Y: 0 max Y: 0
min pressure: 0 max pressure: 1023
device name: TPS6507x Touchscreen
Protocol type A
QTsLibMouseHandler "tslib" ""
- Breakdown of frame time; sync: 370 ms render: 995 ms swap: 0 ms total: 1365 ms time since last frame: 1 ms
- Breakdown of frame time; sync: 3 ms render: 74 ms swap: 1 ms total: 78 ms time since last frame: 99 ms
- Breakdown of frame time; sync: 1 ms render: 68 ms swap: 0 ms total: 69 ms time since last frame: 87 ms
- Breakdown of frame time; sync: 3 ms render: 26 ms swap: 0 ms total: 29 ms time since last frame: 31 ms
- Breakdown of frame time; sync: 1 ms render: 23 ms swap: 1 ms total: 25 ms time since last frame: 26 ms
- Breakdown of frame time; sync: 0 ms render: 49 ms swap: 1 ms total: 50 ms time since last frame: 51 ms
- Breakdown of frame time; sync: 1 ms render: 48 ms swap: 0 ms total: 49 ms time since last frame: 51 ms

When i build this applications on the desktop, CPU usage is constant (10% for other cases).

What i deal whrong? How render every time ONLY OpenGL QSGNode? How tuning EGLFS system for this?

  • 0
    TI__Expert 6580 points

    Do the elements involve transparency ?

  • 0 in reply to Prabindh Sundareson
    Prodigy 60 points

    Thanks for reply!

    No, elements does not transparency.

    I found that this problem is also using QML Canvas Element.

    main.qml:

    Rectangle{

      Canvas{

             Timer { interval: 50; running: true; repeat: true; onTriggered: parent.requestPainting();  }
             onPaint: {           //some JS code for painting         }

      }

    }

    10% CPU usage

    main.qml:

    Rectangle{

      Canvas{

             Timer { interval: 50; running: true; repeat: true; onTriggered: parent.requestPainting();  }
             onPaint: {           //some JS code for painting         }

      }

      MyOtherItems{}

    }

    30% CPU usage !

    Changing Canvas::renderTarget and Canvas::RenderStrategy not give results.


    Ok..  How solve this problem? I need display QML Scene and show 50hz graph (plot) with axes and text marks in front.  Only I need deal this?