I have the start point (x1,y1) and the desired length and angle of the line.
If the angles were directions, 0 degrees is W, 90 is N, 180 is E and 270 is S. I can modify this if needed.
How can I use the start point, length and angle to determine the end point(x2, y2)?
x2 = x1 + 长度cos(角度)
y2 = y1 + 长度sin(角度)
在这种情况下，角度逆时针增加，0 指向正 x。x 轴向右增加，y 轴向上。
对于屏幕：
对于 W = 0、N = 90、E = 180、S = 270：
x2 = x1 - length * cos(angle)
y2 = y1 - length * sin(angle)
对于 E = 0、N = 90、W = 180、S = 270：
x2 = x1 + length * cos(angle)
y2 = y1 - length * sin(angle)
请注意，您需要确保 cos 的实现以度而不是弧度工作，否则您会得到奇怪角度的线条。