[vtkusers] How to get normals??

[David Doria]

On Wed, Nov 11, 2009 at 2:12 AM, renlishen <renlishen at gmail.com> wrote:
>
> I want to generate a personal data
> and how can I get the normals?
>
> my code:
>        vtkImageData *ImageDataSrc = vtkImageData::New() ;
>        vtkMarchingCubes *Iso = vtkMarchingCubes::New() ;
>
>        ImageDataSrc->SetDimensions( 512, 512, 512 ) ;
>        ImageDataSrc->SetScalarType( VTK_UNSIGNED_CHAR ) ;
>
>        ImageDataSrc->AllocateScalars() ;
>
>        ImageDataSrc = CreateSphere(ImageDataSrc, 256, 256, 256,  80, 100, 0 ) ;
>        Iso->SetInput( ImageDataSrc ) ;
>        Iso->SetValue( 0, 100 ) ;
>
>        vtkPolyDataNormals *skinNormals = vtkPolyDataNormals::New();
>        skinNormals->SetInput(Iso->GetOutput());
>        skinNormals->ComputePointNormalsOn() ;
>
>        vtkPolyData *pData = vtkPolyData::New() ;
>        pData->DeepCopy( ( vtkDataSet*)skinNormals->GetOutput() ) ;
>        pData->Update() ;
>        double *a_pointer ;
>        double p_normal[ 3 ] ;
>        a_pointer = p_normal ;
>        pData->GetPointData()->GetNormals()->GetTuple(1, a_pointer) ; <----Is it
> right?
>
> vtkImageData* CVTKMarchingCubeView::CreateSphere(vtkImageData* pTarget, int
> CircleCenterX, int CircleCenterY, int CircleCenterZ, int Radius, int
> FgValue, int BgValue)
> {
>        int SrcDims[3];
>        pTarget->GetDimensions(SrcDims);
>        if(Radius > SrcDims[0] || Radius > SrcDims[1] )
>        {
>                return NULL;
>        }
>        if(CircleCenterX >= SrcDims[0] || CircleCenterY >= SrcDims[1] ||
> CircleCenterZ >= SrcDims[2])
>        {
>                return NULL;
>        }
>
>        unsigned char * pTar = (unsigned char *)pTarget->GetScalarPointer();
>        int r = Radius*Radius;
>        int dx,dy,dz;
>
>        for (int kLoop = 0; kLoop < SrcDims[2]; kLoop++)
>        {
>                for (int iLoop = 0; iLoop < SrcDims[1]; iLoop++)
>                {
>                        for (int jLoop = 0; jLoop < SrcDims[0]; jLoop++)
>                        {
>                                dx = jLoop-CircleCenterX;
>                                dy = iLoop-CircleCenterY;
>                                dz = kLoop-CircleCenterZ;
>                                if(  dx * dx + dy * dy + dz * dz  <= r)
>                                {
>                                        *pTar = FgValue;
>                                }
>                                else
>                                        *pTar = BgValue;
>
>                                pTar++;
>                        }
>                }
>        }
>        return pTarget;
>
> }
>
>
> How can I get the point's normal on the sphere?
> Thanks for your help...
> --

Renlishen,

Typically when you post to the mailing list, it is helpful to extract
a very simple example of what you are trying to do (< 20 lines)?

I have written a little example that looks like it may get you closer
to your goals here:
http://www.vtk.org/Wiki/Add/Get_Normals_to/from_a_Polydata

Let us know if you are still having problems.

Thanks,

David