c# - 线条旋转问题

Question

我有 2 条线是这样画的:

float Alpha = RotDegrees;
PointF PitCenter = new Point(picBoxZoomMap.Width / 2, picBoxZoomMap.Height / 2);
PointF p = new PointF(PitCenter.X - 20, PitCenter.Y - 250);
PointF p2 = new PointF(PitCenter.X + 20, PitCenter.Y - 250);

zoomgfx.DrawLine(Pens.Red, PitCenter, new PointF(
    (float)((p.Y - PitCenter.Y) * Math.Sin(Alpha * Math.PI / 180) + p.X),
    (float)(PitCenter.Y + (p.Y - PitCenter.Y) * Math.Cos(Alpha * Math.PI / 180))));

zoomgfx.DrawLine(Pens.Red, PitCenter, new PointF(
    (float)((p2.Y - PitCenter.Y) * Math.Sin(Alpha * Math.PI / 180) + p2.X),
    (float)(PitCenter.Y + (p2.Y - PitCenter.Y) * Math.Cos(Alpha * Math.PI / 180))));

这是 Alpha = 0 时的行；

这里是旋转 90 度后的线条..

正如你看到的那样，线条以某种方式相遇......我真的不明白为什么...... 有什么想法吗？

Answer 1

您的旋转公式不正确，请看这里 --> Rotate a point by another point in 2D

把你的代码改成这样，你会得到正确的效果:

PointF PitCenter = new Point(picBoxZoomMap.Width / 2, picBoxZoomMap.Height / 2);
PointF p = new PointF(PitCenter.X - 20, PitCenter.Y - 250);
PointF p2 = new PointF(PitCenter.X + 20, PitCenter.Y - 250);

var AlphaRad = RotDegrees * Math.PI / 180;

zoomgfx.DrawLine(Pens.Red, PitCenter, new PointF(
(float)(Math.Cos(AlphaRad) * (p.X - PitCenter.X) - Math.Sin(AlphaRad) * (p.Y - PitCenter.Y) + PitCenter.X),
(float)(Math.Sin(AlphaRad) * (p.X - PitCenter.X) + Math.Cos(AlphaRad) * (p.Y - PitCenter.Y) + PitCenter.Y)));

zoomgfx.DrawLine(Pens.Red, PitCenter, new PointF(
(float)(Math.Cos(AlphaRad) * (p2.X - PitCenter.X) - Math.Sin(AlphaRad) * (p2.Y - PitCenter.Y) + PitCenter.X),
(float)(Math.Sin(AlphaRad) * (p2.X - PitCenter.X) + Math.Cos(AlphaRad) * (p2.Y - PitCenter.Y) + PitCenter.Y)));