C++向量在递归函数中丢失数据

Question

我对C++非常陌生，我试图实现一个TriangleDynamic对象，它可以使用名为splitTriangleProject的函数递归地自我分割。它将自己分解成四个较小的TriangleDynamic对象（并将新三角形的顶点投影到具有给定半径和原点的球体上，但我相信这不在这一点上），将新创建的三角形推入作为原始对象的成员数据。矢量成员数据称为subTriangles。然后，每个子三角形都会调用splitTriangleProject函数，直到发生某个“级别”的分割。

我遇到的问题是只有第一级分割实际上正确推送到subTriangles向量。我确信这个问题与超出范围的媒介有关，或者也许TriangleDynamic超出了范围。我想有一些解决方法，用指针。如果任何人都可以提供帮助，我们将非常感谢。

这里是我的TriangleDynamic声明：

class TriangleDynamic 
{ 
public: 
    TriangleDynamic(const Point &P1, const Point &P2, const Point &P3); 
    TriangleDynamic(); 
    ~TriangleDynamic(){} 
    void printTriangle(); 
    void splitTriangleProject(int currentLevel, int maxLevel, const Point &org, double radius); 
    void init(); 
    bool operator<(const TriangleDynamic&); 
    bool operator>(const TriangleDynamic&); 
    Line edge1; 
    Line edge2; 
    Line edge3; 

    Point p1; 
    Point p2; 
    Point p3; 

    Vect normal; 

    bool lowestLevel; 

    vector<TriangleDynamic> subTriangles; 
    static int numTriangles; 
    int triangleId; 
}; 

int TriangleDynamic::numTriangles = 0; 

和构造函数：

// constructor for the TriangleDynamic object 
TriangleDynamic::TriangleDynamic(const Point &P1, const Point &P2, const Point &P3) 
{ 
    p1 = P1; 
    p2 = P2; 
    p3 = P3; 
    init(); 
} 

TriangleDynamic::TriangleDynamic() 
{ 
    p1 = Point(0,0,0); 
    p2 = Point(0,0,1); 
    p3 = Point(0,1,0); 
    init(); 
} 

void TriangleDynamic::init() 
{ 
    edge1 = Line(p1,p2); 
    edge2 = Line(p2,p3); 
    edge3 = Line(p3,p1); 

    Vect U = p2.minus(p1); 
    Vect V = p3.minus(p1); 

    normal = U.cross(V); 

    lowestLevel = true; 
    triangleId = numTriangles + 1; 
    numTriangles = triangleId; 
} 

这里是我的splitTriangleProject功能：

void TriangleDynamic::splitTriangleProject(int currentLevel, int maxLevel, const Point &org, double radius) 
{ 
    if (currentLevel < maxLevel) 
    { 
     lowestLevel = false; 
     Point worldOrigin = Point(0,0,0); 
     double edge1MidMag = (edge1.midpoint - org).distance(worldOrigin) ; 
     double edge2MidMag = (edge2.midpoint - org).distance(worldOrigin) ; 
     double edge3MidMag = (edge3.midpoint - org).distance(worldOrigin) ; 

     Point newEdge1Mid = (((edge1.midpoint) * radius)/ edge1MidMag) + org; 
     Point newEdge2Mid = (((edge2.midpoint) * radius)/ edge2MidMag) + org; 
     Point newEdge3Mid = (((edge3.midpoint) * radius)/ edge3MidMag) + org; 

     TriangleDynamic t1(p1 , newEdge1Mid , newEdge3Mid); 
     subTriangles.push_back(t1); 

     TriangleDynamic t2(newEdge1Mid, p2, newEdge2Mid); 
     subTriangles.push_back(t2); 

     TriangleDynamic t3(newEdge3Mid, newEdge2Mid, p3); 
     subTriangles.push_back(t3); 

     TriangleDynamic t4(newEdge1Mid, newEdge2Mid, newEdge3Mid); 
     subTriangles.push_back(t4); 

     t1.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
     t2.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
     t3.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
     t4.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    } 
} 

这里是递归打印triangleDynamic功能当它完成时：

void TriangleDynamic::printTriangle() 
{ 
    cout<< "p1"; 
    p1.printPoint(); 
    cout << "\np2"; 
    p2.printPoint(); 
    cout << "\np3"; 
    p3.printPoint(); 
    cout << "\n\n"; 

    if(!lowestLevel) 
    { 
     int ctr; 
     for (ctr=0; ctr<=subTriangles.size()-1; ctr++) 
     { 
      cout << "subTriangle\n"; 
      subTriangles[ctr].printTriangle(); 
     } 
    } 
} 

这是我如何把它在我的主：

int main() 
{ 
    TriangleDynamic t = TriangleDynamic(); 
    t.splitTriangleProject(0,3,Point(), 1); 
    t.printTriangle(); 
    cin.get(); 
    return 0; 
} 

我想我已经贴了太多​​在这一点上。任何帮助表示赞赏，在此先感谢。

Answer 1

问题就在这里

TriangleDynamic t1(p1 , newEdge1Mid , newEdge3Mid); 
    subTriangles.push_back(t1); 

    TriangleDynamic t2(newEdge1Mid, p2, newEdge2Mid); 
    subTriangles.push_back(t2); 

    TriangleDynamic t3(newEdge3Mid, newEdge2Mid, p3); 
    subTriangles.push_back(t3); 

    TriangleDynamic t4(newEdge1Mid, newEdge2Mid, newEdge3Mid); 
    subTriangles.push_back(t4); 

    t1.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t2.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t3.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t4.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 

注意你怎么推三角形的副本到子三角形矢量打电话splitTrangleProject之前。

因此，矢量中的三角形没有对它们调用的splitTriangleProject。

将回传移到代码的末尾，它应该可以工作。

TriangleDynamic t1(p1 , newEdge1Mid , newEdge3Mid); 


    TriangleDynamic t2(newEdge1Mid, p2, newEdge2Mid); 


    TriangleDynamic t3(newEdge3Mid, newEdge2Mid, p3); 


    TriangleDynamic t4(newEdge1Mid, newEdge2Mid, newEdge3Mid); 


    t1.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t2.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t3.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 
    t4.splitTriangleProject(currentLevel + 1, maxLevel, org, radius); 

    subTriangles.push_back(t3); 
    subTriangles.push_back(t2); 
    subTriangles.push_back(t1); 
    subTriangles.push_back(t4); 

（而且，在另一方面，如果这个代码开始变得缓慢它可以极大地加快了C++ 11的std ::举动。不要进入指针，除非你要。）

Answer 2

当您将三角形push_back到矢量中时，它将推送三角形的副本。然后，您将t1递归到t4，但此递归不会影响已被推入向量中的内容，因为它是副本。

Answer 3

在计算splitTriangleProject（）中的子三角之后，您需要检索它们并添加到类的自己的列表（子三角形）中。 像这样：

void splitTriangleProject(int currentLevel, int maxLevel, const Point &org, double radius) 
{ 
// your code above 

subTriangles.insert(subTriangles.begin(), t1.subTriangles.begin(), t1.subTriangles.end()); 
subTriangles.insert(subTriangles.begin(), t2.subTriangles.begin(), t2.subTriangles.end()); 
subTriangles.insert(subTriangles.begin(), t3.subTriangles.begin(), t3.subTriangles.end()); 
subTriangles.insert(subTriangles.begin(), t4.subTriangles.begin(), t4.subTriangles.end()); 

} 

然后，你需要添加额外的访问方法 “常量矢量& getSubTriangles（）”。（现在你似乎将所有成员变量作为公共共享，这不是一个好的做法）