简单的二次B样条曲线

//使用二次B样条曲线生成离散点
vector<Point>& Route::bSpline()
{
    double a0,a1,a2;
    double dt,t1,t2;
    Point tmp_p;

    //使首位相连
    Point *newp = new Point[num_points+2];
    for (int i=0; i<num_points; i++)
    {
        newp[i].setXY(p[i].x, p[i].y);
    }
    newp[num_points].setXY(p[0].x, p[0].y);
    newp[num_points+1].setXY(p[1].x, p[1].y);

    dt=1.0/k;
    tmp_p.setXY((newp[0].x+newp[1].x)/2,(newp[0].y+newp[1].y)/2); //曲线起始点；
    positions.push_back(tmp_p);
    //将结果输出到文件
    ofstream outlog("positons.txt");
    outlog<<"x= "<<tmp_p.x<<"    y= "<<tmp_p.y<<"\n";

    for(int i=1;i<num_points+1;i++)
    {
        for(int j=0;j<=k;j++)
        {  
            t1=j*dt;
            t2=t1*t1;
            
            a0=(t2-2*t1+1)/2.0;
            a1=(2*t1-2*t2+1)/2.0;
            a2=t2/2.0;
            
            double t_x,t_y;
            t_x=a0*newp[i-1].x+a1*newp[i].x+a2*newp[i+1].x;
            t_y=a0*newp[i-1].y+a1*newp[i].y+a2*newp[i+1].y;
            tmp_p.setXY(t_x,t_y);
            outlog<<"x= "<<tmp_p.x<<"    y= "<<tmp_p.y<<"\n";
            positions.push_back(tmp_p);
        }
    }
//    positions.pop_back();
    outlog.close();
    delete [] newp;
    return positions;
}