笔记----圆和矩形碰撞检测

// f：矩形
//    // f_rotation 矩形旋转角度

// c: 圆形
bool collision( float f_x, float f_y, float f_width, float f_height,
    float f_rotation, float c_x, float c_y, float c_radius)
{
    float sint, cost;
    float w, h, rx, ry, r;

    cost = Math.cos(f_rotation);
    sint = Math.sin(f_rotation);

    w = f_width;
    h = f_height;
    r = c_radius;
    rx = (c_x - f_x) * cost + (c_y - f_y) * sint;
    ry = -(c_x - f_x) * sint + (c_y - f_y) * cost;

    float dx = Math.min(rx, w*0.5f);
    dx = Math.max(dx, -w*0.5f);

    float dy = Math.min(ry, h*0.5f);
    dy = Math.max(dy, -h*0.5f);

    return (rx - dx)*(rx - dx) + (ry - dy)*(ry - dy) <= r*r;
}