# OctreeTimingDemo

VTKExamples/Cxx/DataStructures/OctreeTimingDemo

### Description¶

This example runs several closest point queries on octrees with varying MaxPointsPerRegion and plots the result.

Question

### Code¶

OctreeTimingDemo.cxx

#include <vtkSmartPointer.h>
#include <vtkAxis.h>
#include <vtkTimerLog.h>
#include <vtkMath.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkIdList.h>
#include <vtkOctreePointLocator.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>
#include <vtkChartXY.h>
#include <vtkPlot.h>
#include <vtkTable.h>
#include <vtkFloatArray.h>
#include <vtkContextView.h>
#include <vtkContextScene.h>
#include <vtkSphereSource.h>

#include <vector>

static void RandomPointInBounds(vtkPolyData* polydata, double p[3]);
static double TimeOctree(vtkPolyData* polydata, int maxPoints, int numberOfTrials);

int main(int, char *[])
{
/*
*/
vtkSmartPointer<vtkSphereSource>::New();

std::cout << "Timing octree..." << std::endl;
std::vector<std::pair<int, double> > results;
int numberOfTrials = 1000;
for(int i = 1; i < 100; i++)
{
double t = TimeOctree(reader->GetOutput(), i, numberOfTrials);
std::pair<int, double> result(i,t);
results.push_back(result);
}

// Create a table with some points in it
vtkSmartPointer<vtkTable> table =
vtkSmartPointer<vtkTable>::New();

vtkSmartPointer<vtkFloatArray> maxPointsPerRegion =
vtkSmartPointer<vtkFloatArray>::New();
maxPointsPerRegion->SetName("MaxPointsPerRegion");

vtkSmartPointer<vtkFloatArray> runtime =
vtkSmartPointer<vtkFloatArray>::New();
runtime->SetName("Run time");

// Fill in the table with some example values
size_t numPoints = results.size();
table->SetNumberOfRows(static_cast<vtkIdType>(numPoints));
for(size_t i = 0; i < numPoints; ++i)
{
table->SetValue(static_cast<vtkIdType>(i), 0, results[i].first);
table->SetValue(static_cast<vtkIdType>(i), 1, results[i].second);
std::cout << "Put " << results[i].first << " " << results[i].second << " in the table." << std::endl;
}

// Set up the view
vtkSmartPointer<vtkContextView> view =
vtkSmartPointer<vtkContextView>::New();

// Add multiple line plots, setting the colors etc
vtkSmartPointer<vtkChartXY> chart =
vtkSmartPointer<vtkChartXY>::New();
line->SetInputData(table, 0, 1);
line->SetColor(0, 255, 0, 255);
line->SetWidth(3.0);
line->GetXAxis()->SetTitle("Max Points Per Region");
line->GetYAxis()->SetTitle("Run time");

// Set up an interactor and start
view->Render();
view->GetInteractor()->SetRenderWindow(view->GetRenderWindow());
view->GetInteractor()->Initialize();
view->GetInteractor()->Start();

return EXIT_SUCCESS;
}

void RandomPointInBounds(vtkPolyData* polydata, double p[3])
{
double bounds[6];
polydata->GetBounds(bounds);

double x = bounds[0] + (bounds[1] - bounds[0]) * vtkMath::Random(0.0,1.0);
double y = bounds[2] + (bounds[3] - bounds[2]) * vtkMath::Random(0.0,1.0);
double z = bounds[4] + (bounds[5] - bounds[4]) * vtkMath::Random(0.0,1.0);

p[0] = x;
p[1] = y;
p[2] = z;
}

double TimeOctree(vtkPolyData* polydata, int maxPoints, int numberOfTrials)
{
vtkSmartPointer<vtkTimerLog> timer =
vtkSmartPointer<vtkTimerLog>::New();
timer->StartTimer();

vtkMath::RandomSeed(0); // this should be changed to time(NULL) to get random behavior

// Create the tree
vtkSmartPointer<vtkOctreePointLocator> octree =
vtkSmartPointer<vtkOctreePointLocator>::New();
octree->SetDataSet(polydata);
octree->SetMaximumPointsPerRegion(maxPoints);
octree->BuildLocator();

std::cout << "With maxPoints = " << maxPoints << " there are " << octree->GetNumberOfLeafNodes() << " leaf nodes." << std::endl;

for(int i = 0; i < numberOfTrials; i++)
{
double p[3];
RandomPointInBounds(polydata, p);
//vtkIdType iD = octree->FindClosestPoint(p);
octree->FindClosestPoint(p);
}

timer->StopTimer();

std::cout << "Octree took " << timer->GetElapsedTime() << std::endl;

return timer->GetElapsedTime();
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(OctreeTimingDemo)

find_package(VTK COMPONENTS
vtkChartsCore
vtkCommonCore
vtkCommonDataModel
vtkCommonSystem
vtkIOXML
vtkInteractionStyle
vtkRenderingContext2D
vtkRenderingContextOpenGL2
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingOpenGL2
vtkViewsContext2D QUIET)
if (NOT VTK_FOUND)
message("Skipping OctreeTimingDemo: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(OctreeTimingDemo MACOSX_BUNDLE OctreeTimingDemo.cxx ) target_link_libraries(OctreeTimingDemo PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(OctreeTimingDemo PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS OctreeTimingDemo MODULES${VTK_LIBRARIES}
)
endif ()


cd OctreeTimingDemo/build


If VTK is installed:

cmake ..


If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..


Build the project:

make


and run it:

./OctreeTimingDemo


WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.