[vtkusers] I can't change opacity using vtkVolumeRayCastIsosurfaceFunction

[Lisa Avila]

Hello Shwuping Vong,

Nothing is wrong with your code - the vtkVolumeRayCastIsosurfaceFunction 
does not support transparent isosurfaces.

Lisa


At 02:05 PM 5/8/2002, Shwu Ping Vong wrote:
>Hi vtkusers,
>
>Please help me with the following scenario:
>
>I am doing volume rendering using the vtkVolumeRayCastIsosurfaceFunction
>as the ray caster function.  Below is the code I have.  The problem I am
>facing now is no matter what value I give to
>opacityTransferFunction->AddPoint(), the opacity of the object rendered
>stays the same.  If I use vtkVolumeRayCastCompositeFunction instead,
>then I can change the opacity of the object.  Can anyone tell me why
>that is so?  What is wrong with this piece of code?
>
>Thanks in advance,
>Shwuping Vong
>
>=====================================================================
>
>#include "vtkStructuredPointsReader.h"
>#include "vtkPiecewiseFunction.h"
>#include "vtkColorTransferFunction.h"
>#include "vtkVolumeProperty.h"
>#include "vtkVolumeRayCastIsosurfaceFunction.h"
>#include "vtkVolumeRayCastMapper.h"
>#include "vtkVolume.h"
>#include "vtkRenderer.h"
>#include "vtkRenderWindow.h"
>#include "vtkRenderWindowInteractor.h"
>#include "vtkActor.h"
>
>int main()
>{
>
>vtkStructuredPointsReader *reader =  vtkStructuredPointsReader::New();
>  reader-> SetFileName
>("/home/svong/vtk40Data/VTKData/Data/ironProt.vtk");
>
>vtkPiecewiseFunction *opacityTransferFunction =
>vtkPiecewiseFunction::New();
>     opacityTransferFunction-> AddPoint  (0 ,  0);
>     opacityTransferFunction-> AddPoint ( 255,   0.3);
>
>vtkColorTransferFunction *colorTransferFunction =
>vtkColorTransferFunction::New();
>     colorTransferFunction-> AddRGBPoint  ( 0, 1.0, 1.0, 1.0);
>     colorTransferFunction-> AddRGBPoint (255, 1.0, 1.0, 1.0);
>
>vtkVolumeProperty *volumeProperty = vtkVolumeProperty::New();
>     volumeProperty-> SetColor( colorTransferFunction);
>     volumeProperty-> SetScalarOpacity (opacityTransferFunction);
>     volumeProperty-> ShadeOn();
>     volumeProperty-> SetInterpolationTypeToLinear();
>
>vtkVolumeRayCastIsosurfaceFunction *isoFunction =
>vtkVolumeRayCastIsosurfaceFunction::New();
>     isoFunction-> SetIsoValue (128.0);
>
>vtkVolumeRayCastMapper *volumeMapper = vtkVolumeRayCastMapper::New();
>     volumeMapper-> SetInput (reader-> GetOutput());
>     volumeMapper-> SetVolumeRayCastFunction (isoFunction);
>
>vtkVolume *volume = vtkVolume::New();
>     volume-> SetMapper (volumeMapper);
>     volume-> SetProperty( volumeProperty);
>
>vtkRenderer *ren1 = vtkRenderer::New();
>vtkRenderWindow *renWin = vtkRenderWindow::New();
>     renWin-> AddRenderer( ren1);
>     renWin-> SetSize (200, 200);
>vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
>     iren-> SetRenderWindow (renWin);
>
>ren1-> AddVolume (volume);
>ren1-> SetBackground (0.1, 0.2, 0.4);
>renWin-> Render();
>iren-> Initialize();
>iren->Start();
>
>return 0;
>}
>
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