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我有一个粒子系统，我用boost::geometry我的椭圆粒子近似为多边形，然后使用库的交集函数来找到重叠区域。我正在计算一个“内部”和“外部”椭圆（多边形）区域来为每个粒子-粒子相互作用分配一个“势”。

我的潜在功能是：

    double Potential(Cell* current, Cell* next)
{
    double areaRep, areaAtt;
    double distance = Distance(current,next);
    double A1 = current->getLength();
    double B1 = A1/2.0;
    double theta1 = current->getTheta(); //*180.0/M_PI
    double x1 = current->getCurrX();
    double y1 = current->getCurrY();
    double A2 = next->getLength();
    double B2 = A2/2.0;
    double theta2 = next->getTheta();
    double x2 = next->getCurrX();
    double y2 = next->getCurrY();
    polygon_2d poly1, poly2, poly3, poly4;
    double lamda1, lamda2;
    lamda1 = 0.0005; lamda2 = 0.00001;
    if(distance < 2.0*1.5*A1) {
        ellipse2poly(theta1, A1, B1, x1, y1, &poly1);
        ellipse2poly(theta2, A2, B2, x2, y2, &poly2);
        areaRep = getOverlapingAreaPoly(poly1,poly2);
        ellipse2poly(theta1, 1.5*A1, 1.5*B1, x1, y1, &poly3);
        ellipse2poly(theta2, 1.5*A2, 1.5*B2, x2, y2, &poly4);
        areaAtt = getOverlapingAreaPoly(poly3, poly4);
        return (lamda1*areaRep - lamda2*areaAtt); 
    }
    else
        return 0.0;
}

“多边形化”功能是：

int ellipse2poly(double theta, double A1, double B1, double H1, double K1, polygon_2d *po)
{
    using namespace boost::geometry;
    polygon_2d  poly;
    const int n = 20;
    double angle = theta; // cell orientation
    double a = A1; // Long semi-axis length
    double b = B1; // short semi-axis length
    double xc = H1; // current X position
    double yc = K1; // current Y position

    if(!n)
    {
        std::cout << "error ellipse(): n should be >0\n" <<std::endl;
        return 0;
    }
    double t = 0;
    int i = 0;
    double coor[2*n+1][2];

    double x, y;
    double step = M_PI/(double)n;
    double sinphi = sin(angle);
    double cosphi = cos(angle);
    for(i=0; i<2*n+1; i++)
    {   
        x = xc + a*cos(t)*cosphi - b*sin(t)*sinphi;
        y = yc + a*cos(t)*sinphi + b*sin(t)*cosphi;
        coor[i][0] = x;
        coor[i][1] = y;
        t += step;
    }
    assign_points(poly, coor);
    correct(poly);
    *po = poly;
    return 1;
}

返回区域为：

double getOverlapingAreaPoly(polygon_2d poly, polygon_2d poly2)
{
    point_2d cent; //centre of overlaping area
    double overAreaPoly = 0.0;
    typedef std::vector<polygon_2d > polygon_list;
    polygon_list v;

    intersection(poly,poly2,v);
    for (polygon_list::const_iterator it = v.begin(); it != v.end(); ++it)
    {
        centroid(*it, cent);
        overAreaPoly = area(*it);
    }

    return overAreaPoly;
}

只要不是针对同一个细胞（粒子），就会为每个细胞（粒子）调用该函数。以前，使用另一种方法，我的算法的一次迭代对于 100 个粒子的一次迭代大约需要 43 毫秒。现在大约需要 1 分钟（！！！），所以我想我做错了什么！

我只在 Win7 64bit 下的 MSVC2012 中对此进行了测试。我将使用 Qt 4.7.4 报告 Linux Mint。

编辑：我已经用 Qt 4.7.4 在 Linux Mint 上进行了测试，它运行得非常合理；每次迭代可能需要 90-100 毫秒，这很好。不知道win7有什么问题...

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1 回答 1

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I have actually fixed it. I started a new project in Visual Studio and copied all source and header files, recompiled and everything runs smoothly now. I guess radically changing code and adding / subtracting stuff must have some impact...

于 2013-04-19T16:05:35.177 回答