In the next example we'll visualize a complicated equation for a
quadric. The equation is


F(x,y,z) = 0.5*x^2 + 1.0*y^2 + 0.2*z^2 + 0.1*y*z + 0.2*y

To visualize it we sample it over a regular array of points (i.e., a
volume or structured point dataset), and then create iso-contours of
the quadric F(x,y,z) = c, where c is a constant (i.e., the contour
value).


Our visualization network will consist of three filters. The first, vtkSampleFunction, samples the quadric equation. The second, vtkContourFilter, creates iso-contours for 0, 1, 2, or 3D data. The last filter, vtkPolyMapper, maps the data to the graphics system as in our previous example. (We also create an outline around the data for context). 

C++


#include "vtkQuadric.h"
#include "vtkSampleFunction.h"
#include "vtkContourFilter.h"
#include "vtkOutlineFilter.h"
#include "vtkPolyDataMapper.h"
#include "vtkActor.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"
#include "vtkRenderWindowInteractor.h"

void main ()
{
  // -- create the quadric function object --

  // create the quadric function definition
  vtkQuadric *quadric = vtkQuadric::New();
  quadric->SetCoefficients(.5,1,.2,0,.1,0,0,.2,0,0);

  // sample the quadric function
  vtkSampleFunction *sample = vtkSampleFunction::New();
  sample->SetSampleDimensions(50,50,50);
  sample->SetImplicitFunction(quadric);

  // Create five surfaces F(x,y,z) = constant between range specified
  vtkContourFilter *contours = vtkContourFilter::New();
  contours->SetInput(sample->GetOutput());
  contours->GenerateValues(5, 0.0, 1.2);

  // map the contours to graphical primitives
  vtkPolyDataMapper *contMapper = vtkPolyDataMapper::New();
  contMapper->SetInput(contours->GetOutput());
  contMapper->SetScalarRange(0.0, 1.2);

  // create an actor for the contours
  vtkActor *contActor = vtkActor::New();
  contActor->SetMapper(contMapper);

  // -- create a box around the function to indicate the sampling volume --

  // create outline
  vtkOutlineFilter *outline = vtkOutlineFilter::New();
  outline->SetInput(sample->GetOutput());

  // map it to graphics primitives
  vtkPolyDataMapper *outlineMapper = vtkPolyDataMapper::New();
  outlineMapper->SetInput(outline->GetOutput());

  // create an actor for it
  vtkActor *outlineActor = vtkActor::New();
  outlineActor->SetMapper(outlineMapper);
  outlineActor->GetProperty()->SetColor(0,0,0);

  // -- render both of the objects --

  // a renderer and render window
  vtkRenderer *ren1 = vtkRenderer::New();
  vtkRenderWindow *renWin = vtkRenderWindow::New();
  renWin->AddRenderer(ren1);

  // an interactor
  vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
  iren->SetRenderWindow(renWin);

  // add the actors to the scene
  ren1->AddActor(contActor);
  ren1->AddActor(outlineActor);
  ren1->SetBackground(1,1,1); // Background color white

  // render an image (lights and cameras are created automatically)
  renWin->Render();

  // begin mouse interaction
  iren->Start();
}