本篇主要演示使用KdTree查找特定点、位置的K近邻或最近邻,以及用户指定半径范围内查找所有近邻,并计算出距离。
KdTree是计算机科学中用来组织K维数据点集的数据结构。类似二叉树。在三位点云中主要用的是三维的KdTree,这种数据结构能提供快速的查找近邻算法。
代码:
#include <pcl/point_cloud.h>
#include <pcl/kdtree/kdtree_flann.h>
#include <iostream>
#include <vector>
#include <ctime>
int
main (int argc, char** argv)
{
// 根据系统时间创建随机数种子
srand (time (NULL));
// 创建点云对象指针
pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);
// 创建随机点云
cloud->width = 1000;
cloud->height = 1;
cloud->points.resize (cloud->width * cloud->height);
for (size_t i = 0; i < cloud->points.size (); ++i)
{
cloud->points[i].x = 1024.0f * rand () / (RAND_MAX + 1.0f);
cloud->points[i].y = 1024.0f * rand () / (RAND_MAX + 1.0f);
cloud->points[i].z = 1024.0f * rand () / (RAND_MAX + 1.0f);
}
// 创建一个 KdTree 对象
pcl::KdTreeFLANN<pcl::PointXYZ> kdtree;
// 将前面创建的随机点云作为 KdTree 输入
kdtree.setInputCloud (cloud);
// 创建一个随机的点作为查找中心
pcl::PointXYZ searchPoint;
searchPoint.x = 1024.0f * rand () / (RAND_MAX + 1.0f);
searchPoint.y = 1024.0f * rand () / (RAND_MAX + 1.0f);
searchPoint.z = 1024.0f * rand () / (RAND_MAX + 1.0f);
/************K 近邻查找************/
// 这个是近邻个数
int K = 10;
// 创建两个向量,分别存放近邻的索引值、近邻的中心距
std::vector<int> pointIdxNKNSearch(K);
std::vector<float> pointNKNSquaredDistance(K);
std::cout << "K nearest neighbor search at (" << searchPoint.x
<< " " << searchPoint.y
<< " " << searchPoint.z
<< ") with K=" << K << std::endl;
// kdtree.nearestKSearch (searchPoint, K, pointIdxNKNSearch, pointNKNSquaredDistance) 这是执行 K 近邻查找的成员函数,下面一行判断查找成功则执行输出结果
if ( kdtree.nearestKSearch (searchPoint, K, pointIdxNKNSearch, pointNKNSquaredDistance) > 0 )
{
for (size_t i = 0; i < pointIdxNKNSearch.size (); ++i)
std::cout << " " << cloud->points[ pointIdxNKNSearch[i] ].x
<< " " << cloud->points[ pointIdxNKNSearch[i] ].y
<< " " << cloud->points[ pointIdxNKNSearch[i] ].z
<< " (squared distance: " << pointNKNSquaredDistance[i] << ")" << std::endl;
}
/*****在半径范围查找所有近邻点*****/
// 创建两个向量,分别存放近邻的索引值、近邻的中心距
std::vector<int> pointIdxRadiusSearch;
std::vector<float> pointRadiusSquaredDistance;
// 指定随机半径
float radius = 256.0f * rand () / (RAND_MAX + 1.0f);
std::cout << "Neighbors within radius search at (" << searchPoint.x
<< " " << searchPoint.y
<< " " << searchPoint.z
<< ") with radius=" << radius << std::endl;
// kdtree.radiusSearch (searchPoint, radius, pointIdxRadiusSearch, pointRadiusSquaredDistance) 这是执行指定半径范围查找近邻的成员函数,下面一行判断查找成功则执行输出结果
if ( kdtree.radiusSearch (searchPoint, radius, pointIdxRadiusSearch, pointRadiusSquaredDistance) > 0 )
{
for (size_t i = 0; i < pointIdxRadiusSearch.size (); ++i)
std::cout << " " << cloud->points[ pointIdxRadiusSearch[i] ].x
<< " " << cloud->points[ pointIdxRadiusSearch[i] ].y
<< " " << cloud->points[ pointIdxRadiusSearch[i] ].z
<< " (squared distance: " << pointRadiusSquaredDistance[i] << ")" << std::endl;
}
return 0;
}
结果:
K nearest neighbor search at (455.807 417.256 406.502) with K=10
494.728 371.875 351.687 (squared distance: 6578.99)
506.066 420.079 478.278 (squared distance: 7685.67)
368.546 427.623 416.388 (squared distance: 7819.75)
474.832 383.041 323.293 (squared distance: 8456.34)
470.992 334.084 468.459 (squared distance: 10986.9)
560.884 417.637 364.518 (squared distance: 12803.8)
466.703 475.716 306.269 (squared distance: 13582.9)
456.907 336.035 304.529 (squared distance: 16996.7)
452.288 387.943 279.481 (squared distance: 17005.9)
476.642 410.422 268.057 (squared distance: 19647.9)
Neighbors within radius search at (455.807 417.256 406.502) with radius=225.932
494.728 371.875 351.687 (squared distance: 6578.99)
506.066 420.079 478.278 (squared distance: 7685.67)
368.546 427.623 416.388 (squared distance: 7819.75)
474.832 383.041 323.293 (squared distance: 8456.34)
470.992 334.084 468.459 (squared distance: 10986.9)
560.884 417.637 364.518 (squared distance: 12803.8)
466.703 475.716 306.269 (squared distance: 13582.9)
456.907 336.035 304.529 (squared distance: 16996.7)
452.288 387.943 279.481 (squared distance: 17005.9)
476.642 410.422 268.057 (squared distance: 19647.9)
499.429 541.532 351.35 (squared distance: 20389)
574.418 452.961 334.7 (squared distance: 20498.9)
336.785 391.057 488.71 (squared distance: 21611)
319.765 406.187 350.955 (squared distance: 21715.6)
528.89 289.583 378.979 (squared distance: 22399.1)
504.509 459.609 541.732 (squared distance: 22452.8)
539.854 349.333 300.395 (squared distance: 22936.3)
548.51 458.035 292.812 (squared distance: 23182.1)
546.284 426.67 535.989 (squared distance: 25041.6)
577.058 390.276 508.597 (squared distance: 25853.1)
543.16 458.727 276.859 (squared distance: 26157.5)
613.997 387.397 443.207 (squared distance: 27262.7)
608.235 467.363 327.264 (squared distance: 32023.6)
506.842 591.736 391.923 (squared distance: 33260.3)
529.842 475.715 241.532 (squared distance: 36113.7)
485.822 322.623 244.347 (squared distance: 36150.5)
362.036 318.014 269.201 (squared distance: 37493.6)
493.806 600.083 462.742 (squared distance: 38032.3)
392.315 368.085 585.37 (squared distance: 38442.9)
303.826 428.659 533.642 (squared distance: 39392.8)
616.492 424.551 289.524 (squared distance: 39556.8)
320.563 333.216 278.242 (squared distance: 41804.5)
646.599 502.256 424.46 (squared distance: 43948.8)
556.202 325.013 568.252 (squared distance: 44751)
291.27 497.352 515.938 (squared distance: 45463.9)
286.483 322.401 495.377 (squared distance: 45567.2)
367.288 550.421 550.551 (squared distance: 46318.6)
595.122 582.77 394.894 (squared distance: 46938.1)
256.784 499.401 379.931 (squared distance: 47064.1)
430.782 230.854 293.829 (squared distance: 48067.2)
261.051 486.593 329.854 (squared distance: 48612.7)
602.061 327.892 545.269 (squared distance: 48632.4)
347.074 610.994 395.622 (squared distance: 49475.6)
482.876 284.894 583.888 (squared distance: 49718.6)
356.962 247.285 514.959 (squared distance: 50423.7)
282.065 509.488 516.216 (squared distance: 50730.4)
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