多边形围绕中心旋转 [英] Polygon rotation around center

问题描述

hi
我有一个制作多边形的点数组。如何围绕其中心旋转多边形。



我尝试过：

公共函数RotatePoints（_Points（）As Point，_ CenterPoint As Point，_Degree As Double）As Point（）
 Dim Output（）As Point = _Points.Clone（）
 
 Dim Angle As Double =（_ Decree / 180.0）* Math.PI 
索引为整数= 0到Output.Length  -  1 
输出（索引）=新点（数学。 Cos（角度）*（输出（索引）.X  -  _CenterPoint.X））+ _ CenterPoint.X，（Math.Sin（角度）*（输出（索引）.Y  -  _CenterPoint.Y））+ _ CenterPoint.Y）
下一个
 
返回输出
结束函数
 

解决方案

简单：你的算法错了。

见这里：几何操作 - 旋转 [ ^ ]



我建议你你将每个坐标分解成一组单独的行，让X工作 - 显然，使用调试器检查 - 然后重复Y.当两者都工作时，将X和Y的各个阶段合并成单行并创建你的新观点。

特别感谢OriginalGriff

公共函数RotatePoints2（_Points（）As Point ，_CenterPoint As Point，_Degree As Double）As Point（）
 Dim Output（）As Point = _Points.Clone（）
 
 Dim Angle As Double =（_ Decree / 180.0）* Math。 PI 
对于Index As Integer = 0 To Output.Length  -  1 
 Dim Dx As Integer =（输出（索引）.X  -  _CenterPoint.X）
 Dim Dy As Integer =（输出（索引）.Y  -  _CenterPoint.Y）
输出（索引）.X =（Math.Cos（角度）* Dx） - （Math.Sin（角度）* Dy）+ _CenterPoint.X 
输出（索引）.Y =（Math.Sin（角度）* Dx）+（Math.Cos（角度）* Dy）+ _CenterPoint.Y 
下一个
 
返回输出
结束函数
 

hi I have an array of points that makes a polygon. how can i rotate polygon around its center.

What I have tried:

Public Function RotatePoints(_Points() As Point, _CenterPoint As Point, _Degree As Double) As Point()
    Dim Output() As Point = _Points.Clone()

    Dim Angle As Double = (_Degree / 180.0) * Math.PI
    For Index As Integer = 0 To Output.Length - 1
        Output(Index) = New Point((Math.Cos(Angle) * (Output(Index).X - _CenterPoint.X)) + _CenterPoint.X, (Math.Sin(Angle) * (Output(Index).Y - _CenterPoint.Y)) + _CenterPoint.Y)
    Next

    Return Output
End Function

解决方案

Simple: your algorithm is wrong.
See here: Geometric Operations - Rotate[^]

I would suggest that you "break out" each coordinate into a separate set of lines, get X working - obviously, use the debugger to check - and then repeat for Y. When both work, amalgamate the separate stages of X and Y into single lines and create your new point.

Special thanks to OriginalGriff

Public Function RotatePoints2(_Points() As Point, _CenterPoint As Point, _Degree As Double) As Point()
    Dim Output() As Point = _Points.Clone()

    Dim Angle As Double = (_Degree / 180.0) * Math.PI
    For Index As Integer = 0 To Output.Length - 1
        Dim Dx As Integer = (Output(Index).X - _CenterPoint.X)
        Dim Dy As Integer = (Output(Index).Y - _CenterPoint.Y)
        Output(Index).X = (Math.Cos(Angle) * Dx) - (Math.Sin(Angle) * Dy) + _CenterPoint.X
        Output(Index).Y = (Math.Sin(Angle) * Dx) + (Math.Cos(Angle) * Dy) + _CenterPoint.Y
    Next

    Return Output
End Function

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