UG8.5 NX二次开发 OBB算法获取实体的最小包容盒，C++语言实现

下面是C++语言实现的OBB算法获取实体的最小包容盒的示例代码：

#include <iostream>
#include <vector>
#include <Eigen/Core>
#include <Eigen/Eigenvalues>

using namespace std;
using namespace Eigen;

Matrix3f computeCovariance(const vector<Vector3f>& points)
{
    Vector3f mean = Vector3f::Zero();
    for (int i = 0; i < points.size(); ++i) {
        mean += points[i];
    }
    mean /= points.size();

    Matrix3f cov = Matrix3f::Zero();
    for (int i = 0; i < points.size(); ++i) {
        Vector3f p = points[i] - mean;
        cov += p * p.transpose();
    }
    cov /= points.size();

    return cov;
}

void computeOBB(const vector<Vector3f>& points, Matrix3f& orientation, Vector3f& center, Vector3f& halfExtents)
{
    // Compute covariance matrix
    Matrix3f cov = computeCovariance(points);

    // Compute eigenvectors and eigenvalues of covariance matrix
    SelfAdjointEigenSolver<Matrix3f> eigensolver(cov);
    Matrix3f eigenVectors = eigensolver.eigenvectors();
    Vector3f eigenValues = eigensolver.eigenvalues();

    // Determine orientation of OBB
    orientation = eigenVectors;

    // Determine center of OBB
    center = Vector3f::Zero();
    for (int i = 0; i < points.size(); ++i) {
        center += points[i];
    }
    center /= points.size();
    center = orientation.transpose() * center;

    // Determine half-extents of OBB
    halfExtents = Vector3f::Zero();
    for (int i = 0; i < points.size(); ++i) {
        Vector3f p = orientation.transpose() * (points[i] - center);
        halfExtents[0] = max(halfExtents[0], abs(p[0]));
        halfExtents[1] = max(halfExtents[1], abs(p[1]));
        halfExtents[2] = max(halfExtents[2], abs(p[2]));
    }
}

int main()
{
    vector<Vector3f> points = { Vector3f(1, 2, 3), Vector3f(4, 5, 6), Vector3f(7, 8, 9) };

    Matrix3f orientation;
    Vector3f center;
    Vector3f halfExtents;

    computeOBB(points, orientation, center, halfExtents);

    cout << "Orientation:" << endl << orientation << endl;
    cout << "Center: " << center.transpose() << endl;
    cout << "Half-Extents: " << halfExtents.transpose() << endl;

    return 0;
}

其中，`computeCovariance`函数用于计算点云的协方差矩阵，`computeOBB`函数用于计算OBB的方向、中心和半轴长度。函数中使用了Eigen库来进行矩阵和向量计算。