[vtkusers] the code always give erorr : Can't use the ray cast mapper without scalars!

[Bryn Lloyd]

Hi,

Like the message says: Your data needs scalar values, e.g. a data array 
with a scalar value for each point in the unstructured grid. The array 
can be double, float etc.
It must be added to the grid.

example:

vtkDoubleArray *arr = vtkDoubleArray::New();
arr->SetNumberOfTuples(grid->GetNumberOfPoints());
arr->FillComponent(0,value); // e.g. double value = 1.0;
arr->SetName("myarray");
grid->GetPointData()->SetScalars(arr);
// or grid->GetPointData()->AddArray(arr);

Of course you can set something more interesting than a single scalar, 
e.g. the distance to the spheres surface...

Have a look at the mentioned classes (also vtkPointData, vtkCellData).


InfoSeekerr wrote:
> Dear All,
> 
> I wanted to apply traingular mish on sphere , but the  code always give
> erorr : Can't use the ray cast mapper without scalars! , how to fix this
> error please,I used the following code (written in c#) :
>               
>  // volume property
>             int shade = 0,compos =  0,  //Classify First or Interpolate
> First 
>  	        interp = 0;
>  
>            // renderer
>            vtkRenderer ren1= new vtkRenderer();
>            ren1.SetBackground( 1.0, 1.0, 1.0 );
>    
>            // render window
>            vtkRenderWindow renWin = new vtkRenderWindow();
>            renWin.AddRenderer( ren1 );
>            renWin.SetSize( 800, 600 );
>  
>            // interactor
>            vtkRenderWindowInteractor iren1 = new
> vtkRenderWindowInteractor();
>            iren1.SetRenderWindow(renWin);
>  
>            // set up the input file for unstructured grid reader
>                        //1.Create a volume data
>                     // create sphere geometry 
>                     vtkSphereSource sphere = new vtkSphereSource();
>                     sphere.SetRadius(1.0);
>                     sphere.SetThetaResolution(18);
>                     sphere.SetPhiResolution(18);
>                     //2.Apply the tetrahedral mish
>                     vtkPolyData vp = new vtkPolyData();
>            
>             vtkDelaunay3D unstructuredReader = new vtkDelaunay3D();
>             unstructuredReader.SetInput(sphere.GetOutput());
> 
>  
>    // set up opacity transfer function
>    vtkPiecewiseFunction opacityTransferFunction = new 
> vtkPiecewiseFunction();
>    opacityTransferFunction.AddPoint(0,   0.02);
>    opacityTransferFunction.AddPoint(4095.0, 1.0);
>  
>    // set up color transfer function
>    vtkColorTransferFunction colorTransferFunction = new
> vtkColorTransferFunction();
>    colorTransferFunction.AddRGBPoint( 0.0, 0.1, 0.1, 0.1);
>    colorTransferFunction.AddRGBPoint( 4095.0, 1.0, 0.0, 1.0);	
>  
>    // set up volume property
>    vtkVolumeProperty volumeProperty = new vtkVolumeProperty();
>    volumeProperty.SetColor(colorTransferFunction);
>    volumeProperty.SetScalarOpacity(opacityTransferFunction);
>    volumeProperty.SetInterpolationType(interp);
>    volumeProperty.SetShade(shade);
>  
>    // composite function for strucured grid renderer
>    vtkVolumeRayCastCompositeFunction compositeFunction = new
> vtkVolumeRayCastCompositeFunction();
>    compositeFunction.SetCompositeMethod(compos);
>  
>    //unstructuredGridRendering
>   vtkUnstructuredGridVolumeRayCastMapper  volumeUnstructedMapper = new 
> vtkUnstructuredGridVolumeRayCastMapper();
>     //          vtkVolumeRayCastMapper volumeUnstructedMapper = new
> vtk.vtkVolumeRayCastMapper();
>             //volumeUnstructedMapper.set  (compositeFunction);
>            
> volumeUnstructedMapper.SetInputConnection(unstructuredReader.GetOutputPort());
> 
>     
>    vtkVolume volume = new vtkVolume();
>  
>    volume.SetMapper(volumeUnstructedMapper);
>    
>    volume.SetProperty(volumeProperty);
>  
>    // add volume to renderer
>    ren1.AddVolume(volume);
>  
>    renWin.Render();
>  
>    iren1.Start();
>    
>    ren1.Dispose();
>    renWin.Dispose();
>    iren1.Dispose();
>    opacityTransferFunction.Dispose();
>    colorTransferFunction.Dispose();
>    volumeProperty.Dispose();
>    compositeFunction.Dispose();
>     // unstructured grid case
>    volumeUnstructedMapper.Dispose();
>    unstructuredReader.Dispose();
>    volume.Dispose();
>        ///////////////////////////////////////////////
>              
> 
> 


-- 
-------------------------------------------------
Bryn Lloyd
Computer Vision Laboratory
ETH Zürich, Sternwartstrasse 7, ETF C110
CH - 8092 Zürich, Switzerland
Tel: +41 44 63 26668
Fax: +41 44 63 21199
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