C++ Opengl-鼠标拖动绘制平滑圆

我想用鼠标拖动画一个平滑的圆。也就是说，在第一次单击鼠标时，将设置起点，在拖动鼠标时，将更新终点并展开圆。我在某个地方读到过，可以用线条条画画。但那不符合我的要求

简而言之，我需要使用opengl使用给定的两点绘制一个圆的逻辑。

如果您有：

top-left position (X1 Y1) 

及

你也有

diameter (sqrt([X2-X1]^2+[Y2-Y1]^2))
radius (diameter/2)

和中心：

CenterX = X1 + (radius * (sin(-atan2(Y2-Y1,X2-X1))));
CenterY = Y1 + (radius * (cos(-atan2(Y2-Y1,X2-X1))));

从那一点开始，你可以用你喜欢的任何方式从中心画一个半径为给定的圆

double max = 2.0 * PI;
double precision = 0.1;
double current = 0.0;
struct point
{
    double x;
    double y;
};

while(current <= max)
{
    point one;
    point two;
    one.x = Center.x + (radius * (sin(-current)));
    one.y = Center.y + (radius * (cos(-current)));
    current += precision;
    two.x = Center.x + (radius * (sin(-current)));
    two.y = Center.y + (radius * (cos(-current)));

    //draw line between one and two?
    //draw here
}

double max=2.0*PI；
双精度=0.1；
双电流=0.0；
结构点
{
双x；
双y；
};
而（当前绘制线（D3DXVECTOR3（（float）1.x，（float）1.y，1.0），D3DXVECTOR3（（float）2.x，（float）2.y，1.0），0xFFFFFFFF）；
}
//render->EndRender（）；
}

输出：

---

起点和终点代表什么？中心和半径（从起点到终点的距离）还是圆圈边界的左上角和右下角？@Vite Falcon左上角和右下角right@ViteFalcon那么，什么符合你的要求呢？计算机不能画一个完美的圆，它们总是近似的。如果线条条不适合你，最好知道还有什么。

double max = 2.0 * PI;
double precision = 0.1;
double current = 0.0;
struct point
{
    double x;
    double y;
};

while(current <= max)
{
    point one;
    point two;
    one.x = Center.x + (radius * (sin(-current)));
    one.y = Center.y + (radius * (cos(-current)));
    current += precision;
    two.x = Center.x + (radius * (sin(-current)));
    two.y = Center.y + (radius * (cos(-current)));

    //draw line between one and two?
    //draw here
}

//draw fun
{
    struct point
    {
        double x,y;
        point(double x,double y) : x(x), y(y) {}
        point(){ x = 0.0, y = 0.0; }
    };

    point start(100.0,100.0);
    point end(150.0,150.0);
    point center;

    double diameter = sqrt(pow(end.x-start.x,2.0)+pow(end.y-start.y,2.0));
    double radius = diameter/2.0;
    double max = 2.0 * PId;
    double precision = max/180.0;
    double current = 0.0;

    center.x = start.x + (radius * (sin(-atan2(end.y-start.y,end.x-start.x))));
    center.y = start.y + (radius * (cos(-atan2(end.y-start.y,end.x-start.x))));
    //render->BeginRender();
    while(current <= max)
    {
        point one;
        //point two;
        one.x = center.x + (radius * (sin(-current)));
        one.y = center.y + (radius * (cos(-current)));
        render->D3DBox((float)one.x,(float)one.y,1.0f,1.0f,0xFFFFFFFF);//create a dot
        current += precision;
        //two.x = center.x + (radius * (sin(-current)));
        //two.y = center.y + (radius * (cos(-current)));
        //
        //render->DrawLine(D3DXVECTOR3((float)one.x,(float)one.y,1.0),D3DXVECTOR3((float)two.x,(float)two.y,1.0),0xFFFFFFFF);
    }
    //render->EndRender();
}