VTK vtkOBBTree 有向包围盒

vtkOBBTree 有向包围盒

vtkOBBTree是一个包围盒的树，它将体的每个cell分割到每个小的包围盒中，由SetNumberOfBuckets确定每个盒中放多少个 Cell。建立一个vtkOBBTree要先设定DataSet,SetDataSet。然后调用BuildLocator。包围盒精细程度由递归深度 (MaxLevel)以及预先设置的NumberOfBuckets决定。

使用场景：

可以用vtkOBBTree和直线、三角形甚至是另一个vtkOBBTree做相交检测、运算，碰撞检测；

可以用来，获得直线与多边形数据的交点；用来求最近点；等；

1.二个vtkOBBTree 求交：

     vtkOBBTree * targetTree = vtkOBBTree::New();targetTree->SetDataSet(targetPoly);targetTree->BuildLocator();vtkOBBTree * clipTree = vtkOBBTree::New();clipTree->SetDataSet(clipPoly);clipTree->BuildLocator();//使用包围盒求交 ，求交部分在OBBNodeIntersected中。NULL表示不做任何转换clipTree->IntersectWithOBBTree(targetTree,NULL,OBBNodeIntersected,this);//OBBNodeIntersected函数的定义：static int OBBNodeIntersected(vtkOBBNode *, vtkOBBNode *, vtkMatrix4x4 *,void *);

2.官方样例：OBBTreeExtractCells.cxx

使用 vtkOBBTree

IntersectWithLine

获取线和包围盒的交点和交点所在Cell;

vtkOBBTree 返回一条线和数据集的所有交点。如果要最近的相交，则必须手动找到它。在此示例中，我们创建一个球体，并将其与一条直线相交。

这里其实也可以用于求，鼠标点击 Pick 到的点；鼠标的2D点，转成世界坐标，加上相机的点，再延长；也是一条线，求出最近的点；也就是鼠标 Pick 到的点；

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 locatorvtkNew<vtkOBBTree> tree;tree->SetDataSet(sphereSource->GetOutput());tree->BuildLocator();// Intersect the locator with the linedouble 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 intersectionsdouble 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 cellsvtkNew<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.官方样例包围盒可视化

 int maxLevel = 5;// Create the treevtkNew<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 representationvtkNew<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());