[vtkusers] [vtkusers]: Urgent Help: Weird problem withvolume rendering

Thu May 20 10:36:05 EDT 2004

Hi Lisa,

Thanks a lot.  The problem was solved. :-))

As you advised, I set the sample distance in vtkVolumeRayCastMapperapper to be the same as the volume spacing (0.0001 meters/pixel), and the volume shows up, :-).   Looks like the default setting works for my previous data (0.1 spacing), but not in the current set.  That't why we will have to reset it. 

I suggest this to be added in the next release of VTK documentation, as the current documentation and handbook don't mention the importance of this setting (actually not mention at all) in the VTK ray-casting based volume rendering.

Cheers,
Thomas

---------------------- Original Message ------------------------
From: Lisa Avila <lisa.avila at kitware.com>
To: Thomas - Kuiran Chen; John Biddiscombe; Bill Vogler; vtkusers at vtk.org <chent at cs.queensu.ca; jbiddiscombe at skippingmouse.co.uk; vogler at calcreek.com; vtkusers at vtk.org>
Sent: 2004-05-20 09:25:23
Subject: Re: [vtkusers] [vtkusers]: Urgent Help: Weird problem withvolume rendering

Hello Thomas,

You need to set your sample distance on the mapper - otherwise it is likely 
sampling right over your entire volume and hence you see nothing.

Lisa

At 12:55 AM 5/20/2004, Thomas - Kuiran Chen wrote:
>Hi there,
>
>I am encouting an very strange problem in volume rendering.
>
>I've had a vtk volume data stored in vtkStructPoints format.  Previously I 
>set the data spacing in (0.1, 0.1, 0.1) millimeters and used the standard 
>volume rendering method to visualize the volume with no problem (the 
>procedure is stated in the VTK user guide).
>
>But when I set the data spacing to (0.0001, 0.0001, 0.0001) meters, 
>without any other changes to the data, the previously workable volume 
>rendering method won't work (simply show nothing in the visualization).
>
>Any one has any clue what happened here?   Help!!!!!
>
>The following is the little rendering codes to the do the job:
>
>         vtkStructuredPointsReader* StructuredPointsReader = 
> vtkStructuredPointsReader::New();
> 
>StructuredPointsReader->SetFileName("../../DataFactory/data_US_RADIUS_ID1018_SET8_DENSE/3D_VTK/Volume_BINARY_2004_0507_1536.vtk");
>
>         // renderer
>         vtkRenderer *aRenderer = vtkRenderer::New();
>         vtkRenderWindow *renWin = vtkRenderWindow::New();
>         renWin->AddRenderer(aRenderer);
>         vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
>         iren->SetRenderWindow(renWin);
>
>         // Create compositing ray functions
>         vtkVolumeRayCastCompositeFunction *RayCastCompositeFunction = 
> vtkVolumeRayCastCompositeFunction::New();
>         RayCastCompositeFunction->SetCompositeMethodToInterpolateFirst();
>
>         // Create mip ray functions
>         vtkVolumeRayCastMIPFunction *MIPRayCastFunction = 
> vtkVolumeRayCastMIPFunction::New();
>         MIPRayCastFunction->SetMaximizeMethodToScalarValue();
>
>         //  we can use MIP
>         RaycastMapper->SetVolumeRayCastFunction( MIPRayCastFunction );
>         // This is where input data comes in
>         RaycastMapper->SetInput( StructuredPointsReader->GetOutput() 
> );         // This is where input data comes in
>
>         // Create volume
>         vtkVolume *Volume = vtkVolume::New();
>         Volume->SetProperty( VolumeProperty );
>         Volume->SetMapper( RaycastMapper );
>
>         aRenderer->AddProp( Volume );
>
>         // Camera setup
>         vtkCamera *aCamera = vtkCamera::New();
>         aCamera->SetViewUp (0, 0, -1);
>         aCamera->SetPosition (0, 1, 0);
>         aCamera->SetFocalPoint (0, 0, 0);
>         aCamera->ComputeViewPlaneNormal();
>
>         aRenderer->SetActiveCamera(aCamera);
>         aRenderer->ResetCamera ();
>
>         // Background setup
>         aRenderer->SetBackground(0,0,0);
>         renWin->SetSize(800, 600);
>
>         aRenderer->ResetCameraClippingRange ();
>
>         // interact with data
>         iren->Initialize();
>         iren->Start();
>
>
>Thanks,
>Thomas
>
>
>
>---------------------- Original Message ------------------------
>From: John Biddiscombe <jbiddiscombe at skippingmouse.co.uk>
>To: Bill Vogler; vtkusers at vtk.org <vogler at calcreek.com; vtkusers at vtk.org>
>Sent: 2004-05-19 16:57:41
>Subject: Re: [vtkusers] Need Help with vtkPlaneSource Sizing
>
>Use
>SetOrigin(0.0, 0.0, 0.0)
>SetPoint1(10.0, 0.0, 0.0 );
>SetPoint2(0.0, 34.0, 0.0 );
>
>and then
>SetXResolution(10);
>SetYResolution(340);
>
>and you'll get a plane with 10x340 quadrilaterals with dimensions 1.0x0.1
>
>When you change the resolution, you change the number of quadrilaterals, but
>the area covered is still controlled by point1,point2 and origin
>
>JB
>
>
>----- Original Message -----
>From: "Bill Vogler" <vogler at calcreek.com>
>To: <vtkusers at vtk.org>
>Sent: Wednesday, May 19, 2004 9:41 PM
>Subject: [vtkusers] Need Help with vtkPlaneSource Sizing
>
>
> > Hello -
> >
> > I am having problems sizing a plane created with vtkPlaneSource. The
>created
> > plane is of fixed size and I can't change the size using the member
>function
> > SetResolution();
> >
> > My understanding of a vtkPlaneSource is that it is an array of "m x n"
> > quadrilaterals located on the specified plane. By default the width and
> > height is of length one (1) and the resolution of the plane is controlled
>by
> > XResolution and YResolution (which are both integers).
> >
> > I would like to specify the width and height with a specific dimension of
> > real numbers (i.e., doubles). Therefore I am a bit confused why the
> > dimensions of the plane do not change is response to a SetResolution()
>call.
> > I am also a bit confused on how to specify this dimension using integers.
> >
> > TIA
> >
> > Bill
> >
> > _______________________________________________
> > This is the private VTK discussion list.
> > Please keep messages on-topic. Check the FAQ at:
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> >
> >
>
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