VTK 的探针类 vtkProbeFilter

这个类是一个计算指定点位置的属性（标量、向量等）。

需要两个输入 ： 数据源、指定的点集。

指定点的属性根据数据源的值通过插值计算得到。

例如，我们可以计算一个体的某一个面的值。

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int main(int, char *[])
{
	// Create a random set of 100 points in the xy-plane in (0,10)x(0,10).
	// If you had instead started with a set of (x,y,z) points, you must copy
	// the zvalues into a FloatArray and set it as the data set's scalars,
	// and then set the z-coordinates to zero
	vtkSmartPointer randomPoints =
		vtkSmartPointer::New();

	vtkSmartPointer zvalues =
		vtkSmartPointer::New();
	zvalues->SetName("ZValues");

	unsigned int gridSize = 10;
	float maxHeight = 5;
	for (unsigned int i = 0; i < 100; ++i)
	{
		double x = vtkMath::Random(0, gridSize);
		double y = vtkMath::Random(0, gridSize);
		double z = vtkMath::Random(0, maxHeight);

        // 两种不同的电集会产生不同的结果
        // 因为这个点集是赋值给数据源，探测点还是 （x, y, 0）
        // 当数据源的 Z 轴值为非零值时，探测的结果属性值都为0
		//randomPoints->InsertNextPoint ( x, y, z);
		randomPoints->InsertNextPoint(x, y, 0);
		zvalues->InsertNextValue(z);
	}

	// Add the grid points to a polydata object
	vtkSmartPointer randomPolyData =
		vtkSmartPointer::New();
	randomPolyData->SetPoints(randomPoints);
	randomPolyData->GetPointData()->SetScalars(zvalues);

	// Triangulate the grid points. If you do not have a mesh (points
	// only), the output will not be interpolated!
	vtkSmartPointer randomDelaunay =
		vtkSmartPointer::New();
#if VTK_MAJOR_VERSION <= 5
	randomDelaunay->SetInput ( randomPolyData );
#else
	randomDelaunay->SetInputData(randomPolyData);
#endif
	randomDelaunay->Update();

	// Create a grid of points to interpolate over
	vtkSmartPointer gridPoints =
		vtkSmartPointer::New();
	for (unsigned int x = 0; x < gridSize; x++)
	{
		for (unsigned int y = 0; y < gridSize; y++)
		{
			gridPoints->InsertNextPoint(x, y, 0);
		}
	}

	// Create a dataset from the grid points
	vtkSmartPointer gridPolyData =
		vtkSmartPointer::New();
	gridPolyData->SetPoints(gridPoints);

	// Perform the interpolation
	vtkSmartPointer probeFilter =
		vtkSmartPointer::New();
	probeFilter->SetSourceConnection(randomDelaunay->GetOutputPort());
#if VTK_MAJOR_VERSION <= 5
	probeFilter->SetInput(gridPolyData); //
	// Interpolate 'Source' at these points
#else
	probeFilter->SetInputData(gridPolyData); //
	// Interpolate 'Source' at these points
#endif
	probeFilter->Update();

	// Map the output zvalues to the z-coordinates of the data so that
	// we get a surface, rather than a flat grid with interpolated
	// scalars.
	vtkSmartPointer gridWarpScalar =
		vtkSmartPointer::New();
	gridWarpScalar->SetInputConnection(probeFilter->GetOutputPort());
	gridWarpScalar->Update();

	 Setup outputs 
	// Output random points
	// Map the output zvalues to the z-coordinates of the data
	vtkSmartPointer randomWarpScalar =
		vtkSmartPointer::New();
	randomWarpScalar->SetInputConnection(randomDelaunay->GetOutputPort());
	randomWarpScalar->Update();

	vtkSmartPointer randomWriter =
		vtkSmartPointer::New();
	randomWriter->SetFileName("randomSurface.vtp");
	randomWriter->SetInputConnection(randomWarpScalar->GetOutputPort());
	randomWriter->Write();

	// Mesh the output grid points
	vtkSmartPointer gridDelaunay =
		vtkSmartPointer::New();
	gridDelaunay->SetInputConnection(gridWarpScalar->GetOutputPort());

	vtkSmartPointer gridWriter =
		vtkSmartPointer::New();
	gridWriter->SetFileName("gridSurface.vtp");
	gridWriter->SetInputConnection(gridDelaunay->GetOutputPort());
	gridWriter->Write();

	// Setup visualization 
	vtkSmartPointer randomMapper =
		vtkSmartPointer::New();
	randomMapper->SetInputConnection(randomWarpScalar->GetOutputPort());
	randomMapper->ScalarVisibilityOff();

	vtkSmartPointer randomActor =
		vtkSmartPointer::New();
	randomActor->SetMapper(randomMapper);
	randomActor->GetProperty()->SetColor(1.0, 0.0, 0.0); //(R,G,B)
	randomActor->GetProperty()->SetPointSize(3);
	randomActor->GetProperty()->SetOpacity(.3);

	vtkSmartPointer gridMapper =
		vtkSmartPointer::New();
	gridMapper->SetInputConnection(gridDelaunay->GetOutputPort());
	gridMapper->ScalarVisibilityOff();

	vtkSmartPointer gridActor =
		vtkSmartPointer::New();
	gridActor->SetMapper(gridMapper);
	gridActor->GetProperty()->SetColor(0.0, 1.0, 1.0); //(R,G,B)
	gridActor->GetProperty()->SetPointSize(3);

	vtkSmartPointer renderer =
		vtkSmartPointer::New();
	vtkSmartPointer renderWindow =
		vtkSmartPointer::New();
	renderWindow->AddRenderer(renderer);
	vtkSmartPointer renderWindowInteractor =
		vtkSmartPointer::New();
	renderWindowInteractor->SetRenderWindow(renderWindow);

	vtkSmartPointer style =
		vtkSmartPointer::New();
	renderWindowInteractor->SetInteractorStyle(style);

	renderer->AddActor(randomActor);
	renderer->AddActor(gridActor);

	renderWindow->Render();
	renderWindowInteractor->Start();

	return EXIT_SUCCESS;
}

如果探测点的生成变成了（和源数据只是覆盖某些地方）：

// Create a grid of points to interpolate over
	vtkSmartPointer gridPoints =
		vtkSmartPointer::New();
	for (unsigned int x = 0; x < gridSize; x++)
	{
		for (unsigned int y = 0; y < gridSize; y++)
		{
			gridPoints->InsertNextPoint(x + 5, y + 5, 0);
		}
	}