[vtk-developers] QVTKWidget with virtualgl

[Clinton Stimpson]

That code only gets called if you want to draw the vtk scene into 
something other than the QVTKWidget.
So its direct rendering, except when you want to copy it into another 
QPaintDevice such as a QImage or QPixmap.  QPixmap::grabWidget() is a 
way to invoke that code.
Under normal use, it really is doing direct rendering.

I've also seen artifacts and trashed windows like yours when using 
compiz on Linux, and interestingly, I don't see it until a 4th child 
window is created, and your example has 4 child windows.

Clint

shiva sitamraju wrote:
> I am pasting code from QVTKWidget.cxx  void 
> QVTKWidget::resizeEvent(QResizeEvent* e)  function from vtk-5.4.
> As you can see it is calling this->mRenWin->GetRGBACharPixelData(0, 0, 
> w-1, h-1, 1, pixels); 
>
>
>   // In Qt 4.1+ let's support redirected painting
> #if QT_VERSION >= 0x040100
>   // if redirected, let's grab the image from VTK, and paint it to the 
> device
>   QPaintDevice* device = QPainter::redirected(this);
>   if(device != NULL && device != this)
>     {
>     int w = this->width();
>     int h = this->height();
>     QImage img(w, h, QImage::Format_RGB32);
>     vtkUnsignedCharArray* pixels = vtkUnsignedCharArray::New();
>     pixels->SetArray(img.bits(), w*h*4, 1);
>     this->mRenWin->GetRGBACharPixelData(0, 0, w-1, h-1, 1, pixels);
>     pixels->Delete();
>     img = img.rgbSwapped();
>     img = img.mirrored();
>     
>     QPainter painter(this);
>     painter.drawImage(QPointF(0.0,0.0), img);
>     return;
>
> On Wed, Apr 8, 2009 at 3:32 AM, Clinton Stimpson <clinton at elemtech.com 
> <mailto:clinton at elemtech.com>> wrote:
>
>
>     Could be a bug in vglrun ??
>     I don't know what readback you're referring to.  Its supposed to
>     render directly.
>
>     Clint
>
>     shiva sitamraju wrote:
>
>         Hi ,
>
>         We are using QVTKWidget in our application and running our
>         application remotely using vglrun.  Without using vglrun
>         everything is fine. I dont know if this is a problem with vtk
>         or virtualgl, but here are the issues:
>
>         1. With vglrun the QVTKWidget display isn't getting refreshed
>         properly (see the attached image)
>         2. Also I see that QVTKWidget is doing a readback and then
>         painting the qtwidget everytime refresh is performed.
>         I guess this readback maybe causing problems with virtualgl.
>         Is there a way to make VTK directly render to a qt opengl
>         context instead of doing a readback.
>
>         Thanks,
>         Shiva
>
>
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