[vtkusers] jittering of vtkVolume when changing vtkCamera azimuth angle

[Michael Yip]

Hi,

I've been having a problem when trying to animate a 360 degree pan of
ray-casted vtkVolume. What happens is that the volume itself seems to be
jittering as the camera pans around. The bounding box for it however, does
not jitter. Heres the code that I am using:

#include <vtkSmartPointer.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkVolume16Reader.h>
#include <vtkVolume.h>
#include <vtkVolumeRayCastMapper.h>
#include <vtkVolumeRayCastCompositeFunction.h>
#include <vtkVolumeProperty.h>
#include <vtkColorTransferFunction.h>
#include <vtkPiecewiseFunction.h>
#include <vtkDataSetReader.h>
#include <vtkCamera.h>
#include <vtkBoundingBox.h>
#include <vtkOutlineFilter.h>
#include <vtkDataSetMapper.h>
#include <vtkAVIWriter.h>
#include <vtkWindowToImageFilter.h>

int main (int argc, char *argv[])
{
    vtkRenderer* aren = vtkRenderer::New();
    vtkRenderWindow *renWin = vtkRenderWindow::New();
    renWin->AddRenderer(aren);
    renWin->SetSize(800,640);

    vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
    iren->SetRenderWindow(renWin);

    aren->SetBackground(0.8, 0.8, 0.8);

    vtkDataSetReader *reader = vtkDataSetReader::New();
    reader->DebugOff();

reader->SetFileName("C:\\Coursework\\Coursework\\Research\\vtkVolumes\\output_vol.vtk");

//reader->SetFileName("C:\\Users\\Michael\\Desktop\\Coursework\\Research\\vtkVolumes\\output_vol.vtk");
    reader->Update();

    vtkPiecewiseFunction *oTFun = vtkPiecewiseFunction::New();
    oTFun->AddSegment(80, 0.0, 255, 1.0);
    oTFun->AddSegment(0, 255, 0, 0);

    vtkVolumeProperty *volProperty = vtkVolumeProperty::New();
    volProperty->SetScalarOpacity(oTFun);
    volProperty->SetInterpolationTypeToLinear();
    volProperty->ShadeOn();


    vtkVolumeRayCastCompositeFunction *cpf =
    vtkVolumeRayCastCompositeFunction::New();

    vtkVolumeRayCastMapper *volmap = vtkVolumeRayCastMapper::New();
    volmap->SetInput(reader->GetOutput());
    volmap->SetVolumeRayCastFunction(cpf);

    vtkVolume *vol = vtkVolume::New();
    vol->SetMapper(volmap);
    vol->SetProperty(volProperty);

    //create a bounding box
    vtkOutlineFilter* outline = vtkOutlineFilter::New();
    outline->SetInput(volmap->GetDataSetInput());
    outline->Update();
    vtkDataSetMapper* outlineMapper = vtkDataSetMapper::New();
    outlineMapper->SetInput(outline->GetOutput());
    vtkActor* outlineActor = vtkActor::New();
    outlineActor->SetMapper(outlineMapper);


    //Add actors to renderWindow
    aren->AddActor(outlineActor);
    aren->AddVolume(vol);

    //Camera
    vtkCamera* camera = aren->GetActiveCamera();
    camera->SetFocalPoint(vol->GetCenter());
    camera->Zoom(1);
    camera->SetPosition(0,200,1000);

    vtkWindowToImageFilter *imageFilter = vtkWindowToImageFilter::New();
    imageFilter->SetInput(renWin);
    vtkAVIWriter *avi=vtkAVIWriter::New();
    avi->SetFileName("c:/TestAVIWriter.avi");
    avi->SetInputConnection(imageFilter->GetOutputPort());
    avi->Start();

    for(int i = 0; i < 360 ; i++){
        printf("i = %d\n", i);
        renWin->Render();
        camera->Azimuth(1.0);
        imageFilter->Modified();
        avi->Write();
    }
    avi->End();
    printf("Finished...");

    /*Cleanup*/
    avi->Delete();
    imageFilter->Delete();
    camera->Delete();
    vol->Delete();
    volmap->Delete();
    cpf->Delete();
    volProperty->Delete();
    oTFun->Delete();
    reader->Delete();
    renWin->Delete();
    aren->Delete();
}


The input file is at:
http://www.ece.ubc.ca/~myip/work/output_vol.vtk

Also, I have a avi video of the output at:
http://www.ece.ubc.ca/~myip/work/TestAVIWriter.avi

Does anyone know what might be causing this? Did I forget to set some sort
of render parameter? Thanks,

Mike
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