Adding LCS example

examples/lagrangian_structures/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.8...3.14 FATAL_ERROR)
+project(ParticleAdvection CXX)
+
+#Find the VTK-m package
+find_package(VTKm REQUIRED QUIET)
+
+add_executable(ftle LagrangianStructures.cxx)
+target_link_libraries(ftle PRIVATE vtkm_cont vtkm_worklet)
+vtkm_add_target_information(ftle
+                            MODIFY_CUDA_FLAGS
+                            DEVICE_SOURCES  LagrangianStructures.cxx)
+if(TARGET vtkm::tbb)
+  target_compile_definitions(ftle PRIVATE BUILDING_TBB_VERSION)
+endif()

examples/lagrangian_structures/LagrangianStructures.cxx

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+#include <cmath>
+#include <string>
+#include <vector>
+
+#include <vtkm/cont/ArrayCopy.h>
+#include <vtkm/cont/DataSet.h>
+#include <vtkm/cont/DataSetBuilderUniform.h>
+#include <vtkm/cont/DataSetFieldAdd.h>
+#include <vtkm/io/reader/VTKDataSetReader.h>
+#include <vtkm/io/writer/VTKDataSetWriter.h>
+
+#include <vtkm/filter/LagrangianStructures.h>
+
+int main(int argc, char** argv)
+{
+  if (argc < 3)
+  {
+    std::cout << "Usage : flte <input dataset> <vector field name>" << std::endl;
+  }
+  std::string datasetName(argv[1]);
+  std::string variableName(argv[2]);
+
+  std::cout << "Reading input dataset" << std::endl;
+  vtkm::cont::DataSet input;
+  vtkm::io::reader::VTKDataSetReader reader(datasetName);
+  input = reader.ReadDataSet();
+  std::cout << "Read input dataset" << std::endl;
+
+  vtkm::filter::LagrangianStructures lcsFilter;
+  lcsFilter.SetStepSize(0.025);
+  lcsFilter.SetNumberOfSteps(500);
+  lcsFilter.SetAdvectionTime(0.025 * 500);
+  lcsFilter.SetActiveField(variableName);
+
+  vtkm::cont::DataSet output = lcsFilter.Execute(input);
+  vtkm::io::writer::VTKDataSetWriter writer("out.vtk");
+  writer.WriteDataSet(output);
+  std::cout << "Written output dataset" << std::endl;
+
+  return 0;
+}