vtkOBBTree directed bounding box
vtkOBBTree is a tree of bounding boxes, which divides each cell of the body into each small bounding box. SetNumberOfBuckets determines how many Cells are placed in each box. To create a vtkOBBTree, you must first set DataSet and SetDataSet. Then call BuildLocator. The fineness of the bounding box is determined by the recursion depth (MaxLevel) and the preset NumberOfBuckets.
Usage scenario:
You can use vtkOBBTree to perform intersection detection, calculation, and collision detection with a straight line, triangle, or even another vtkOBBTree;
It can be used to obtain the intersection point of straight line and polygon data; used to find the closest point; etc.;
1. Intersection of two vtkOBBTree:
vtkOBBTree * targetTree = vtkOBBTree::New();
targetTree->SetDataSet(targetPoly);
targetTree->BuildLocator();
vtkOBBTree * clipTree = vtkOBBTree::New();
clipTree->SetDataSet(clipPoly);
clipTree->BuildLocator();
//Use the bounding box to intersect, and the intersection part is in OBBNodeIntersected. NULL means no conversion is performed
clipTree->IntersectWithOBBTree(targetTree,NULL,OBBNodeIntersected,this);
//Definition of OBBNodeIntersected function:
static int OBBNodeIntersected(vtkOBBNode *, vtkOBBNode *, vtkMatrix4x4 *,void *);
2. Official sample: OBBTreeExtractCells.cxx
Use vtkOBBTree
IntersectWithLine
Get the intersection point of the line and the bounding box and the Cell where the intersection point is located;
vtkOBBTree returns all intersection points of a line and a data set. If you want the closest intersection, you have to find it manually. In this example, we create a sphere and intersect it with a straight line.
In fact, it can also be used here to find the point reached by clicking the mouse; the 2D point of the mouse is converted into world coordinates, plus the point of the camera, and then extended; it is also a line, and the nearest point is found; that is, the point reached by the mouse Pick point;
CODE
#include <vtkExtractCells.h>
#include <vtkIdList.h>
#include <vtkLine.h>
#include <vtkLineSource.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOBBTree.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkSphereSource.h>
#include <vtkActor.h>
#include <vtkDataSetMapper.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
int main(int, char*[])
{
vtkNew<vtkNamedColors> colors;
vtkNew<vtkSphereSource> sphereSource;
sphereSource->SetPhiResolution(7);
sphereSource->SetThetaResolution(15);
sphereSource->Update();
//Create the locator
vtkNew<vtkOBBTree> tree;
tree->SetDataSet(sphereSource->GetOutput());
tree->BuildLocator();
// Intersect the locator with the line
double lineP0[3] = {-0.6, -0.6, -0.6};
double lineP1[3] = {.6, .6, .6};
vtkNew<vtkPoints> intersectPoints;
vtkNew<vtkIdList> intersectCells;
double tol = 1.e-8;
tree->SetTolerance(tol);
tree->IntersectWithLine(lineP0, lineP1, intersectPoints, intersectCells);
std::cout << "NumPoints: " << intersectPoints->GetNumberOfPoints()
<< std::endl;
// Display list of intersections
double intersection[3];
for (int i = 0; i < intersectPoints->GetNumberOfPoints(); i + + )
{
intersectPoints->GetPoint(i, intersection);
std::cout << "\tPoint Intersection " << i << ": " << intersection[0] << ", "
<< intersection[1] << ", " << intersection[2] << std::endl;
}
std::cout << "NumCells: " << intersectCells->GetNumberOfIds() << std::endl;
vtkIdType cellId;
for (int i = 0; i < intersectCells->GetNumberOfIds(); i + + )
{
cellId = intersectCells->GetId(i);
std::cout << "\tCellId " << i << ": " << cellId << std::endl;
}
// Render the line, sphere and intersected cells
vtkNew<vtkLineSource> lineSource;
lineSource->SetPoint1(lineP0);
lineSource->SetPoint2(lineP1);
vtkNew<vtkPolyDataMapper> lineMapper;
lineMapper->SetInputConnection(lineSource->GetOutputPort());
vtkNew<vtkActor> lineActor;
lineActor->SetMapper(lineMapper);
vtkNew<vtkPolyDataMapper> sphereMapper;
sphereMapper->SetInputConnection(sphereSource->GetOutputPort());
vtkNew<vtkActor> sphereActor;
sphereActor->SetMapper(sphereMapper);
sphereActor->GetProperty()->SetRepresentationToWireframe();
sphereActor->GetProperty()->SetColor(colors->GetColor3d("Gold").GetData());
vtkNew<vtkExtractCells> cellSource;
cellSource->SetInputConnection(sphereSource->GetOutputPort());
cellSource->SetCellList(intersectCells);
vtkNew<vtkDataSetMapper> cellMapper;
cellMapper->SetInputConnection(cellSource->GetOutputPort());
vtkNew<vtkActor> cellActor;
cellActor->SetMapper(cellMapper);
cellActor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->AddRenderer(renderer);
vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);
renderer->AddActor(lineActor);
renderer->AddActor(sphereActor);
renderer->AddActor(cellActor);
renderer->SetBackground(colors->GetColor3d("CornflowerBlue").GetData());
renderWindow->SetWindowName("OBBTreeExtractCells");
renderWindow->Render();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}
3.Official sample bounding box visualization
int maxLevel = 5;
//Create the tree
vtkNew<vtkOBBTree> obbTree;
obbTree->SetDataSet(polyData);
obbTree->SetMaxLevel(maxLevel);
obbTree->BuildLocator();
double corner[3] = {0.0, 0.0, 0.0};
double max[3] = {0.0, 0.0, 0.0};
double mid[3] = {0.0, 0.0, 0.0};
double min[3] = {0.0, 0.0, 0.0};
double size[3] = {0.0, 0.0, 0.0};
obbTree->ComputeOBB(polyData, corner, max, mid, min, size);
//Initialize the representation
vtkNew<vtkPolyData> polydata;
obbTree->GenerateRepresentation(0, polydata);
vtkNew<vtkPolyDataMapper> obbtreeMapper;
obbtreeMapper->SetInputData(polydata);
vtkNew<vtkActor> obbtreeActor;
obbtreeActor->SetMapper(obbtreeMapper);
obbtreeActor->GetProperty()->SetInterpolationToFlat();
obbtreeActor->GetProperty()->SetOpacity(.5);
obbtreeActor->GetProperty()->EdgeVisibilityOn();
obbtreeActor->GetProperty()->SetColor(
colors->GetColor4d("SpringGreen").GetData());