#include <vtkPoints.h>
#include <vtkPointData.h>
#include <vtkDelaunay2D.h>
#include <vtkLookupTable.h>

#include <vtkPolyData.h>
#include <vtkPolyDataNormals.h>
#include <vtkPolyDataMapper.h>

#include <vtkWarpScalar.h>

#include <vtkCamera.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

#include <vtkInteractorStyleTerrain.h>

#include <vtkSmartPointer.h>
#include <vtkDoubleArray.h>
 
 
void TriangulateTerrain();

int main (int argc, char ** argv)
{
	TriangulateTerrain();	
	return 0;
}
  
void TriangulateTerrain()
{
 
	vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  vtkSmartPointer<vtkDoubleArray> scalars = vtkSmartPointer<vtkDoubleArray>::New();
 
	unsigned int GridSize = 50;
	for(double x = -3; x < 3; x += 6.0/GridSize)
	{
		for(double y = -3; y < 3; y += 6.0/GridSize)
		{
      double z = sin(x*y);
			vtkIdType idx = points->InsertNextPoint(x, y, z);
      scalars -> InsertTuple(idx, &z);
		}
 
	}
 
	//add the grid points to a polydata object
	vtkPolyData* polydata = vtkPolyData::New();
	polydata->SetPoints(points);
  polydata->GetPointData() -> SetScalars(scalars);
 
	//triangulate the grid points
	vtkDelaunay2D* delaunay = vtkDelaunay2D::New();
	delaunay->SetInput(polydata);
	delaunay->Update();

  //Normals for Gourad shading
  vtkPolyDataNormals* normals = vtkPolyDataNormals::New();
  normals -> SetInputConnection(delaunay ->GetOutputPort() );
  normals -> SetFeatureAngle(60);

  //Set the colours for the rendering
  vtkLookupTable* lut = vtkLookupTable::New();
  lut -> SetHueRange(0.66667, 0.0);
  lut -> SetNumberOfColors(256);
  lut -> SetRampToLinear();
  lut -> Build();

  
	// map the contours to graphical primitives
	vtkPolyDataMapper *contMapper = vtkPolyDataMapper::New();
  contMapper->SetInput(normals -> GetOutput() );
  contMapper->SetScalarRange(0,1);
  contMapper->SetLookupTable(lut);
  contMapper->ImmediateModeRenderingOn();

 
 	 // create an actor for the contours
	vtkActor *contActor = vtkActor::New();
	contActor->SetMapper(contMapper);
 
	  // 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);
  
  //The style
  vtkInteractorStyleTerrain *terrain_style = vtkInteractorStyleTerrain::New();
 
	// add the actors to the scene
	ren1->SetBackground(0.6,0.6,0.6); 
  ren1->GetActiveCamera()->SetViewUp(0,0,1);
  ren1->GetActiveCamera()->SetParallelProjection(1);
	ren1->AddActor(contActor);
  iren -> SetInteractorStyle(terrain_style);
  ren1->ResetCamera();

 
  	// render an image (lights and cameras are created automatically)
	renWin->Render();
 
  	// begin mouse interaction
	iren->Start();
 
}