0

我正在用鼠标旋转一个圆圈，但我希望对圆圈的旋转范围有一个限制。（假设是 3 个完整的时间）。当它达到极限时，它不能再朝同一个方向转动，但可以朝相反的方向转动。我让它在最大转弯后停止，但现在我试图找到方向，每次我的鼠标经过圆圈的 x 轴时，方向都会改变，因为 atan2 给了我相对于 x 轴的角度。所以新的鼠标位置在一个象限，最后一个位置在另一个象限，所以减去这些角度并不能得到我想要的。我解释清楚了吗？有什么建议么？

private void HelmPb_MouseMove(object sender, MouseEventArgs e)
    {
        if ((e.Button != MouseButtons.Left) || _dontTurn) return;
        double angle = OffsetAngle();
        Point temp = MousePosition;
        float degrees = Convert.ToSingle(angle - _offsetAngle);
        float diff = _lastHelmAngle - degrees;
        float absDiff = Math.Abs(diff) % 360;
        if (absDiff > 180) absDiff = 360 - absDiff;
        double angle1 = Math.Atan2(_lastHelmPoint.Y, _lastHelmPoint.X);
        if (angle1 < 0) angle1 += 2*Math.PI;
        double angle2 = Math.Atan2(temp.Y, temp.X);
        if (angle2 < 0) angle2 += 2*Math.PI;
        double direction = angle1 - angle2;
        direction = direction*(180/Math.PI);
        _deltaHelmTurn += Convert.ToSingle(absDiff);
        if (_deltaHelmTurn >= (_maxHelmTurn*360.0))
        {
            if (direction > 0 && _lastHelmDirection > 0)
            {
                _deltaHelmTurn = Convert.ToSingle(_maxHelmTurn*360.0);
                degrees = Convert.ToSingle(_maxHelmTurn*360.0)%360;
            }
        }
        _lastHelmDirection = direction;
        _lastHelmPoint = MousePosition;
        _lastHelmAngle = Convert.ToSingle(degrees);
        _sameHelmRotation = Convert.ToSingle(degrees);
        HelmPb.Image.Dispose();
        WaterDepthPlot.Update();
        HelmPb.Image = RotateImage(_originalHelmImage, -degrees);
        HelmPb.Update();
    }

private double OffsetAngle()
    {
        int helmXMid = HelmPb.PointToScreen(Point.Empty).X + (HelmPb.Width / 2);
        int helmYMid = HelmPb.PointToScreen(Point.Empty).Y + (HelmPb.Height / 2);
        double angle = AngleFromPoints(MousePosition, new Point(helmXMid, helmYMid));
        return angle;
    }

private double AngleFromPoints(Point pt1, Point pt2)
    {
        Point p = new Point(pt1.X - pt2.X, pt1.Y - pt2.Y);
        double alpha;
        if (p.Y == 0) alpha = p.X > 0 ? 0d : 180d;
        else
        {
            double f = 1d * p.X / (Math.Sqrt(p.X * p.X + p.Y * p.Y));
            alpha = Math.Acos(f) * 180d / Math.PI;
            if (p.Y > 0) alpha = 360d - alpha;
        }
        return alpha;
    }
4

1 回答 1

0

两个向量之间的旋转方向等价于它们叉积的符号。

//Returns 1 for CCW, -1 for CW, 0 for no change
private int Direction(Point from, Point to)
{
    double cross = (from.x * to.y) - (from.y * to.x);
    return Math.Sign(cross);
}
于 2015-06-04T15:26:22.487 回答