[vtkusers] splines

[Dean Inglis]

sorry, I missed that.

Maybe it's because you call Reset()
without setting the number of points.


  if(spline_points) spline_points->Reset();      float t = 0.0;
     for(int i=0; i<numberOfOutputPoints;i++)
     {
        t = ( (float)numberOfInputPoints - 1.0 ) / (
(float)numberOfOutputPoints - 1.0 ) * (float)i;
       spline_points->SetPoint(i, splineX->Evaluate(t),
splineY->Evaluate(t), splineZ->Evaluate(t));

       float* pt = spline_points->GetPoint(i);


If you do

  points->Initialize();
or
  points->Reset();

you must then do
  points->SetNumberOfPoints( npoints ); // pre-allocate memory

before calling
  points->SetPoint(i,x,y,z);  // when memmory is pre-allocated (faster)

if you do not set the number of points, you can do
  points->InsertNextPoint(x,y,z); //allocate memory as required (slower)


Dean



Hi,

Thanks for your reply. But your are wrong: I set:

 t = ( (float)numberOfInputPoints - 1.0 ) / ( (float)numberOfOutputPoints -
1.0 ) * (float)i;
       spline_points->SetPoint(i, splineX->Evaluate(t),
splineY->Evaluate(t), splineZ->Evaluate(t));

Is it not correct? Any other idea?

Isabelle





dean.inglis at camris.ca a écrit :
you didn't define any points:

//Generate the polyline for the spline.
spline_points = vtkPoints::New();
spline_points->SetNumberOfPoints( static_cast(numberOfOutputPoints) );

you need to also do:

spline_points->SetPoint(i,somethingX,somethingY,somethingZ);

or,

double somethingXYZ[3];
spline_points->SetPoint(i,somethingXYZ);

Dean


>
Hi,

I am really confused about interpolating my glyph points with a spline.

I look a lot of examples on this and I thought having understood, but
actually, only my glyph are drawn.

I put a TRACE instruction to see what is computed after calling
spline-.Evaluate(): i got crazy values except for the first one: not so
amazing that nothing is drawn!

Here is what I did:


   splineX = vtkCardinalSpline::New();
   splineY = vtkCardinalSpline::New();
   splineZ = vtkCardinalSpline::New();

    numberOfOutputPoints = 20; //Number of points on the spline

 //Generate the polyline for the spline.
 spline_points = vtkPoints::New();
 spline_points->SetNumberOfPoints(
static_cast<vtkIdType>(numberOfOutputPoints) );

 //Create the polyline.
 spline_lines = vtkCellArray::New();
 spline_lines->InsertNextCell(numberOfOutputPoints);

 for(int i=0; i<numberOfOutputPoints;i++)
  spline_lines->InsertCellPoint(i);//add points one at a time

 spline_polyData = vtkPolyData::New();
 spline_polyData->SetPoints(spline_points);
 spline_points->Delete();
 spline_polyData->SetLines(spline_lines);
 spline_lines->Delete();

 //Add thickness to the resulting line.
    tubes = vtkTubeFilter::New();
    tubes->SetInput(spline_polyData);
    tubes->SetRadius(0.075);
    tubes->SetNumberOfSides(6);

 vtkPolyDataMapper* spline_mapper = vtkPolyDataMapper::New();
    spline_mapper->SetInput(tubes->GetOutput());
 tubes->Delete();

 splines = vtkActor::New();
 splines->SetMapper(spline_mapper);
 spline_mapper->Delete();

 splines->GetProperty()->SetColor(1.0, 0.0, 1.0);

And after each click:
case vtkCommand::LeftButtonPressEvent:
     {
        vtkRenderWindowInteractor  *interactor =
reinterpret_cast<vtkRenderWindowInteractor *>(caller);
       int x = interactor->GetEventPosition()[0];
       int y = interactor->GetEventPosition()[1];

        // Convert display point to world point
       double world_point[4];
       m_Renderer->SetDisplayPoint( x, y, 0 );
       m_Renderer->DisplayToWorld();
       m_Renderer->GetWorldPoint( world_point );

      // Store the point with no range checking or memory allocation.
      points->SetPoint( nodeId, world_point[0], world_point[1],
world_point[2] );

      // Create a vertex for each node. This type of cell has a single
point.
      vtkIdType topology[1];
      topology[0] = nodeId;
      vertices->InsertNextCell( 1, topology );

     //create new points
     numberOfInputPoints = points->GetNumberOfPoints();

     if ( numberOfInputPoints >= 2 )
     {
        if(numberOfInputPoints==2)
        {
         m_Renderer->AddActor( splines );
         splines->Delete();
        }

      splineX->RemoveAllPoints();
      splineY->RemoveAllPoints();
      splineZ->RemoveAllPoints();

      for ( int i = 0 ; i < numberOfInputPoints; i++)
     {
     //add coordinates points to the splines.
     float* point = points->GetPoint(i);
     splineX->AddPoint( i, point[0] );
     splineY->AddPoint( i, point[1] );
     splineZ->AddPoint( i, point[2] );
     }

     if(spline_points) spline_points->Reset();
     float t = 0.0;
     for(int i=0; i<numberOfOutputPoints;i++)
     {
        t = ( (float)numberOfInputPoints - 1.0 ) / (
(float)numberOfOutputPoints - 1.0 ) * (float)i;
       spline_points->SetPoint(i, splineX->Evaluate(t),
splineY->Evaluate(t), splineZ->Evaluate(t));

       float* pt = spline_points->GetPoint(i);
      TRACE("spline points:%f %f %f\n", pt[0], pt[1], pt[2]);
  }

    spline_polyData->Modified();
}

   nodeId++;
   m_glyphActor->VisibilityOn();
   splines->VisibilityOn();
   this->Render();
  }
  break;

- Does someone see what is wrong? Insofar as my glyph are correcly drawn, I
assume that my input points are correct. So what's wrong?

Please help me,

Isabelle
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