[vtkusers] How to turn volume data into triangle data (Not triangle strip)
Amy Squillacote
amy.squillacote at kitware.com
Fri Apr 1 16:04:15 EST 2005
Hi Jeffrey,
Why are you passing your data through vtkStripper and then through
vtkTriangleFilter? This creates triangle strips and then breaks them back
apart. When vtkTriangleFilter breaks the triangle strips apart, it copies
the cell data values of the entire triangle strip to each triangle that was
a part of that strip. In VTK, a triangle strip is a single cell; there is
not separate cell data per triangle composing that strip. If what you mean
by "the cell data still seems like triangle strips" is that the same value
is repeated for each triangle that was in a particular strip, this should
explain why. If that is not what you mean, please clarify.
- Amy
At 03:46 PM 4/1/2005, Jeffrey Meng wrote:
>Hi Amy,
>
>Thank you for your reply.
>
>I transfered the data to triangles, and try to iterate through the
>celldata, but the cell
>data still seems like triangle strips, would you please have a quick
>look at my source
>listed below?
>
>Thanks a million.
>
>Best,
>Jeffrey
>
>===============================================================
>Command line parameter: VTK_DATA_ROOT/headsq/Quarter
>
>#include "vtkRenderer.h"
>#include "vtkRenderWindow.h"
>#include "vtkRenderWindowInteractor.h"
>#include "vtkVolume16Reader.h"
>#include "vtkPolyDataMapper.h"
>#include "vtkActor.h"
>#include "vtkOutlineFilter.h"
>#include "vtkCamera.h"
>#include "vtkStripper.h"
>#include "vtkLookupTable.h"
>#include "vtkImageDataGeometryFilter.h"
>#include "vtkProperty.h"
>#include "vtkPolyDataNormals.h"
>#include "vtkContourFilter.h"
>#include "vtkImageData.h"
>#include "vtkImageMapToColors.h"
>#include "vtkImageActor.h"
>#include "vtkPolyData.h"
>#include "vtkCellData.h"
>#include "vtkPointData.h"
>#include "vtkPointDataToCellData.h"
>#include "vtkCellPicker.h"
>#include "vtkCommand.h"
>#include "vtkTriangleFilter.h"
>
>class vtkMyCallback : public vtkCommand
>{
>public:
> static vtkMyCallback* New()
> {
> return new vtkMyCallback;
> }
>
> void SetCellPicker(vtkCellPicker* pPicker)
> {
> _pCellPicker = pPicker;
> }
>
> virtual void Execute(vtkObject* caller, unsigned long, void*)
> {
> if (NULL == _pCellPicker)
> {
> return;
> }
>
> vtkRenderer* pRenderer =
> reinterpret_cast<vtkRenderer*>(caller);
> if (NULL == pRenderer)
> {
> return;
> }
>
> vtkRenderWindow* pRenderWindow =
> pRenderer->GetRenderWindow();
> if (NULL == pRenderWindow)
> {
> return;
> }
>
> if (_pCellPicker->GetCellId() < 0 )
> {
> printf("Cell ID = %d\n", _pCellPicker->GetCellId());
> }
> else
> {
> float coordinates[3] = {0.0f};
> _pCellPicker->GetSelectionPoint(coordinates);
> float x = coordinates[0];
> float y = coordinates[1];
>
> float* position = _pCellPicker->GetPickPosition();
> float xp = position[0];
> float yp = position[1];
> float zp = position[2];
>
> printf("Pick Position = %f\t%f\t%f\n", xp, yp, zp);
> }
>
> //pRenderWindow->Render();
> }
>
>private:
> vtkCellPicker* _pCellPicker;
>};
>
>int main (int argc, char **argv)
>{
> if (argc < 2)
> {
> cout << "Usage: " << argv[0] << " DATADIR/headsq/quarter"
> << endl;
> return 1;
> }
>
>
>////////////////////////////////////////////////////////////////////////////
>
> // Now we are creating three orthogonal planes passing through the
> // volume. Each plane uses a different texture map and therefore has
> // diferent coloration.
>
> // Start by creatin a black/white lookup table.
> vtkLookupTable* bwLut = vtkLookupTable::New();
> bwLut->SetTableRange(0, 2000);
> bwLut->SetSaturationRange(0, 0);
> bwLut->SetHueRange(0, 0);
> bwLut->SetValueRange(0, 1);
> bwLut->Build();
>
> // Now create a lookup table that consists of the full hue circle
> // (from HSV).
> vtkLookupTable* hueLut = vtkLookupTable::New();
> hueLut->SetTableRange(0, 2000);
> hueLut->SetHueRange(0, 1);
> hueLut->SetSaturationRange(1, 1);
> hueLut->SetValueRange(1, 1);
> hueLut->Build();
>
> // Finally, create a lookup table with a single hue but having a
> range
> // in the saturation of the hue.
> vtkLookupTable* satLut = vtkLookupTable::New();
> satLut->SetTableRange(0, 2000);
> satLut->SetHueRange(.6, .6);
> satLut->SetSaturationRange(0, 1);
> satLut->SetValueRange(1, 1);
> satLut->Build();
>
>
>////////////////////////////////////////////////////////////////////////////
>
> // Create the renderer, the render window, and the interactor. The
> // renderer draws into the render window, the interactor enables
> // mouse- and keyboard-based interaction with the data within the
> // render window.
> //
> vtkRenderer* aRenderer = vtkRenderer::New();
> vtkRenderWindow* renWin = vtkRenderWindow::New();
> renWin->AddRenderer(aRenderer);
>
> vtkRenderWindowInteractor* iren = vtkRenderWindowInteractor::New();
> iren->SetRenderWindow(renWin);
>
>
>////////////////////////////////////////////////////////////////////////////
>
> // The following reader is used to read a series of 2D slices
> (images)
> // that compose the volume. The slice dimensions are set, and the
> // pixel spacing. The data Endianness must also be specified. The
> // reader usese the FilePrefix in combination with the slice
> number to
> // construct filenames using the format FilePrefix.%d. (In this case
> // the FilePrefix is the root name of the file: quarter.)
> vtkVolume16Reader* v16 = vtkVolume16Reader::New();
> v16->SetDataDimensions(64,64);
> v16->SetDataByteOrderToLittleEndian();
> v16->SetFilePrefix(argv[1]);
> v16->SetImageRange(1, 93);
> v16->SetDataSpacing(3.2, 3.2, 1.5);
>
>
>////////////////////////////////////////////////////////////////////////////
>
> // An isosurface, or contour value of 500 is known to correspond to
> // the skin of the patient. Once generated, a vtkPolyDataNormals
> // filter is is used to create normals for smooth surface shading
> // during rendering. The triangle stripper is used to create
> triangle
> // strips from the isosurface; these render much faster on may
> // systems.
> vtkContourFilter* skinExtractor = vtkContourFilter::New();
> skinExtractor->SetInput(v16->GetOutput());
> skinExtractor->SetValue(0, 500);
>
> vtkPolyDataNormals* skinNormals = vtkPolyDataNormals::New();
> skinNormals->SetInput(skinExtractor->GetOutput());
> skinNormals->SetFeatureAngle(60.0);
>
> vtkStripper* skinStripper = vtkStripper::New();
> skinStripper->SetInput(skinNormals->GetOutput());
>
> vtkTriangleFilter* pTriangles = vtkTriangleFilter::New();
> pTriangles->SetInput(skinStripper->GetOutput());
> pTriangles->PassLinesOn();
> pTriangles->PassVertsOn();
>
> //*
> vtkPointDataToCellData* pPoint2Cell = vtkPointDataToCellData::New();
> pPoint2Cell->SetInput(pTriangles->GetOutput());
> pPoint2Cell->PassPointDataOn();
> //*/
>
> bool bUsePointData = false;
>
> vtkPolyDataMapper* skinMapper = vtkPolyDataMapper::New();
> if (bUsePointData)
> {
> skinMapper->SetInput(skinStripper->GetOutput());
> }
> else
> {
> skinMapper->SetInput(pPoint2Cell->GetPolyDataOutput());
> //skinMapper->SetInput(pTriangles->GetOutput());
> }
>
> skinMapper->ScalarVisibilityOn();
> skinMapper->SetLookupTable(hueLut);
> if (bUsePointData)
> {
> skinMapper->SetScalarModeToUsePointData();
> }
> else
> {
> skinMapper->SetScalarModeToUseCellData();
> }
> skinMapper->UseLookupTableScalarRangeOn();
> skinMapper->Update();
>
> try
> {
> vtkPolyData* pPolyData = skinMapper->GetInput();
> printf("vtkPolyData Type = %s\n",
> skinMapper->GetInput()->GetClassName());
>
> vtkCellData* pCellData = pPolyData->GetCellData();
> vtkDataArray* pCellArray = pCellData->GetScalars();
>
> vtkPointData* pPointData = pPolyData->GetPointData();
> vtkDataArray* pPointArray = pPointData->GetScalars();
>
> double scalar[] = {0.0};
>
> if (bUsePointData)
> {
> //int nComponents =
> pPointArray->GetNumberOfComponents();
> int nTuples = pPointArray->GetNumberOfTuples();
>
> //for (int i = 0; i < nComponents; ++i)
> {
> for (int j = 0; j < nTuples / 2; ++j)
> {
> //pPointArray->SetComponent(0, j,
> 0.0);
> pPointArray->SetTuple(j, scalar);
> }
> }
>
> pPointArray->Modified();
> }
> else
> {
> int nTuples = pCellArray->GetNumberOfTuples();
> for (int i = 0; i < nTuples / 2; ++i)
> {
> pCellArray->SetTuple(i, scalar);
> }
>
> pCellArray->Modified();
> }
>
> pPolyData->Modified();
> skinMapper->Update();
> }
> catch (...)
> {
> printf("Exception thrown\n");
> }
>
>
>//------------------------------------------------------------------------\\
> // Create a cell picker
> //
> vtkCellPicker* pPicker = vtkCellPicker::New();
> vtkMyCallback* pPickCallback = vtkMyCallback::New();
> pPickCallback->SetCellPicker(pPicker);
> pPicker->AddObserver(vtkCommand::EndPickEvent, pPickCallback);
>
>
> vtkActor* skin = vtkActor::New();
> skin->SetMapper(skinMapper);
> skin->GetProperty()->SetDiffuseColor(1, .49, .25);
> skin->GetProperty()->SetSpecular(.3);
> skin->GetProperty()->SetSpecularPower(20);
>
>
>////////////////////////////////////////////////////////////////////////////
>
> // Create the first of the three planes. The filter
> vtkImageMapToColors
> // maps the data through the corresponding lookup table created
> above. The
> // vtkImageActor is a type of vtkProp and conveniently displays
> an image on
> // a single quadrilateral plane. It does this using texture
> mapping and as
> // a result is quite fast. (Note: the input image has to be
> unsigned char
> // values, which the vtkImageMapToColors produces.) Note also that by
> // specifying the DisplayExtent, the pipeline requests data of
> this extent
> // and the vtkImageMapToColors only processes a slice of data.
> vtkImageMapToColors* saggitalColors = vtkImageMapToColors::New();
> saggitalColors->SetInput(v16->GetOutput());
> saggitalColors->SetLookupTable(bwLut);
> vtkImageActor* saggital = vtkImageActor::New();
> saggital->SetInput(saggitalColors->GetOutput());
> saggital->SetDisplayExtent(16, 16, 0, 63, 0, 92);
>
> // Create the second (axial) plane of the three planes. We use the
> // same approach as before except that the extent differs.
> vtkImageMapToColors *axialColors = vtkImageMapToColors::New();
> axialColors->SetInput(v16->GetOutput());
> axialColors->SetLookupTable(hueLut);
> vtkImageActor *axial = vtkImageActor::New();
> axial->SetInput(axialColors->GetOutput());
> axial->SetDisplayExtent(0,63, 0,63, 46,46);
>
> // Create the third (coronal) plane of the three planes. We use
> // the same approach as before except that the extent differs.
> vtkImageMapToColors *coronalColors = vtkImageMapToColors::New();
> coronalColors->SetInput(v16->GetOutput());
> coronalColors->SetLookupTable(satLut);
> vtkImageActor *coronal = vtkImageActor::New();
> coronal->SetInput(coronalColors->GetOutput());
> coronal->SetDisplayExtent(0,63, 32,32, 0,92);
>
> // It is convenient to create an initial view of the data. The
> // FocalPoint and Position form a vector direction. Later on
> // (ResetCamera() method) this vector is used to position the camera
> // to look at the data in this direction.
> vtkCamera* aCamera = vtkCamera::New();
> aCamera->SetViewUp (0, 0, -1);
> aCamera->SetPosition (0, 1, 0);
> aCamera->SetFocalPoint (0, 0, 0);
> aCamera->ComputeViewPlaneNormal();
>
> // Actors are added to the renderer.
> aRenderer->AddActor(saggital);
> aRenderer->AddActor(axial);
> aRenderer->AddActor(coronal);
> aRenderer->AddActor(skin);
>
> // Set skin to semi-transparent.
> skin->GetProperty()->SetOpacity(0.5);
>
> // An initial camera view is created. The Dolly() method moves
> // the camera towards the FocalPoint, thereby enlarging the image.
> aRenderer->SetActiveCamera(aCamera);
> aRenderer->ResetCamera();
> aCamera->Dolly(1.5);
>
> // Set a background color for the renderer and set the size of the
> // render window (expressed in pixels).
> aRenderer->SetBackground(1,1,1);
> renWin->SetSize(300, 300);
>
> // Note that when camera movement occurs (as it does in the Dolly()
> // method), the clipping planes often need adjusting. Clipping planes
> // consist of two planes: near and far along the view direction. The
> // near plane clips out objects in front of the plane; the far plane
> // clips out objects behind the plane. This way only what is drawn
> // between the planes is actually rendered.
> aRenderer->ResetCameraClippingRange();
>
> pPicker->Pick(85, 126, 0, aRenderer);
>
> // Interact with data
> iren->Initialize();
> iren->SetPicker(pPicker);
> iren->Start();
>
> // Cleanup
> v16->Delete();
> skinExtractor->Delete();
> skinNormals->Delete();
> skinStripper->Delete();
> skinMapper->Delete();
> skin->Delete();
> bwLut->Delete();
> hueLut->Delete();
> satLut->Delete();
> saggitalColors->Delete();
> saggital->Delete();
> axialColors->Delete();
> axial->Delete();
> coronalColors->Delete();
> coronal->Delete();
> aCamera->Delete();
> aRenderer->Delete();
> renWin->Delete();
> iren->Delete();
>
> return 0;
>}
>
>
> >Hi Jeffrey,
> >
> >vtkTriangleFilter is supposed to output triangles, not triangle strips. If
> >this is not the behavior you are seeing, something is wrong.
> >
> >- Amy
>_______________________________________________
>This is the private VTK discussion list.
>Please keep messages on-topic. Check the FAQ at:
>http://www.vtk.org/Wiki/VTK_FAQ
>Follow this link to subscribe/unsubscribe:
>http://www.vtk.org/mailman/listinfo/vtkusers
More information about the vtkusers
mailing list