[vtkusers] Windows offscreen image rendering

[John Biddiscombe]

     renWin->SetupMemoryRendering(width, height, 
(HDC)renWin->GetGenericContext());
     renWin->Render();
// do stuff with bitmap
     renWin->ResumeScreenRendering();


I have used this successfully, but note that it stopped working some time 
(I don't know when - I didn't use it for months) and when I tried it last 
week it gave an image of width & height of zero (ie nothing). I checked in 
a fix a few days ago and my offscreen rendering is working fine again. 
maybe you should try a nightly release from today or similar and give it a go.

If you're using an older vtk, you should probably just get 
vtkWin32OpenGLRenderWindow from cvs

(Note that the above assumes you already have a compatible device context 
on screen, if you are doing vtk without a window you might need something 
else...)

JB


At 09:00 08/09/2001, =?utf-8?Q?Ermin_Hasi=C4=8Devi=C4=87?= wrote:
>Hi!
>
>I would like to render a sequence of images in offscreen mode
>using VTK on Windows platform. But it seems I can't just simply
>tell vtkWin32OpenGLImageWindow to render images offscreen.
>I have tried to set memory rendering by calling
>SetupMemoryRendering(xsize, ysize, NULL) but after calling
>Render method on image window I still get window opened
>and don't know how to prevent it's opening.
>
>What modifications should I make to following code to achieve
>offscreen rendering of images?
>
>      vtkCellArray *segResCellArr = vtkCellArray::New();
>         vtkPolyData *segResPD = vtkPolyData::New();
>         //vtkExtentTranslator *segResExtTr = vtkExtentTranslator::New();
>         vtkPolyDataMapper2D *segResMapper = vtkPolyDataMapper2D::New();
>         vtkActor2D *segResActor = vtkActor2D::New();
>         vtkImager *segResImager = vtkImager::New();
>         vtkWin32OpenGLImageWindow *segResWnd =
>vtkWin32OpenGLImageWindow::New();
>         vtkWindowToImageFilter *segResWnd2Img;
>         vtkImageAppend *segResImgApp = vtkImageAppend::New();
>         vtkImageBlend *segResImgBlend = vtkImageBlend::New();
>         vtkBMPWriter *segResWriter = vtkBMPWriter::New();
>         segResImgApp->SetAppendAxis(2);
>         segResImgApp->Update();
>         segResWnd->AddImager(segResImager);
>         segResWnd->SetSize(MaxCoord[0] + 1, MaxCoord[1] + 1);
>         segResWriter->SetFilePrefix((InputDirectory + "SEGRes" +
>BMPInputFilePrefix).c_str());
>         segResWriter->SetFilePattern("%s_%03d.bmp");
>         int n = VFTemplatesRadioGroup->ItemIndex;
>         int contour_no = deformSurfsPD[n]->GetNumberOfCells();
>         int segRes_point_no;
>         int *segRes_ptIds;
>         for(int i = 0; i < contour_no; i ++) {
>                 segRes_point_no =
>deformSurfsPD[n]->GetCell(i)->GetNumberOfPoints();
>                 segRes_ptIds = new int[segRes_point_no + 1];
>                 for(int j = 0; j < segRes_point_no; j ++) {
>                         segRes_ptIds[j] = j;
>                 }
>                 segRes_ptIds[segRes_point_no] = 0;
>                 segResCellArr->Initialize();
>                 segResCellArr->InsertNextCell(segRes_point_no + 1,
>segRes_ptIds);
>
>segResPD->SetPoints(deformSurfsPD[n]->GetCell(i)->GetPoints());
>                 segResPD->SetLines(segResCellArr);
>                 segResPD->Update();
>                 segResMapper->SetInput(segResPD);
>                 segResActor->SetMapper(segResMapper);
>                 segResImager->AddActor2D(segResActor);
>                 segResWnd->Render();
>                 segResWnd2Img = vtkWindowToImageFilter::New();
>                 segResWnd2Img->SetInput(segResWnd);
>                 segResWnd2Img->Update();
>                 segResImgApp->AddInput(segResWnd2Img->GetOutput());
>                 segResImgApp->Update();
>                 segResWnd2Img->Delete();
>                 segResImager->RemoveActor2D(segResActor);
>         }
>         segResImgBlend->SetInput(0, OrigImgData);
>         segResImgBlend->SetInput(1, segResImgApp->GetOutput());
>         segResImgBlend->SetOpacity(1, 0.2);
>         segResImgBlend->Update();
>         segResWriter->SetInput(segResImgBlend->GetOutput());
>         segResWriter->Write();
>         segResCellArr->Delete();
>         segResPD->Delete();
>         segResMapper->Delete();
>         segResActor->Delete();
>         segResImager->Delete();
>         segResWnd->Delete();
>         segResImgBlend->Delete();
>         segResWriter->Delete();
>
>BTW. Does anybody know how to accelerate vtkBMPWriter. It takes him
>about 20 seconds
>for 20 50kB images.
>
>Thanks in advance.
>
>Ermin
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