# kingBook

## unity 凸多形顶点排序

/// <summary>
/// 多边形点集排序
/// </summary>
/// <param name="vPoints"></param>
/// <returns></returns>
public List<Point> SortPolyPoints(List<Point> vPoints)
{
if (vPoints == null || vPoints.Count == 0) return null;
//计算重心
Point center = new Point();
double X = 0, Y = 0;
for (int i = 0; i < vPoints.Count; i++)
{
X += vPoints[i].X;
Y += vPoints[i].Y;
}
center = new Point((int)X / vPoints.Count, (int)Y / vPoints.Count, vPoints[0].Z);
//冒泡排序
for (int i = 0; i < vPoints.Count - 1; i++)
{
for (int j = 0; j < vPoints.Count - i - 1; j++)
{
if (PointCmp(vPoints[j], vPoints[j + 1], center))
{
Point tmp = vPoints[j];
vPoints[j] = vPoints[j + 1];
vPoints[j + 1] = tmp;
}
}
}
return vPoints;
}

/// <summary>
/// 若点a大于点b,即点a在点b顺时针方向,返回true,否则返回false
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <param name="center"></param>
/// <returns></returns>
private bool PointCmp(Point a, Point b, Point center)
{
if (a.X >= 0 && b.X < 0)
return true;
else if (a.X == 0 && b.X == 0)
return a.Y > b.Y;
//向量OA和向量OB的叉积
double det = (a.X - center.X) * (b.Y - center.Y) - (b.X - center.X) * (a.Y - center.Y);
if (det < 0)
return true;
if (det > 0)
return false;
//向量OA和向量OB共线，以距离判断大小
double d1 = (a.X - center.X) * (a.X - center.X) + (a.Y - center.Y) * (a.Y - center.Y);
double d2 = (b.X - center.X) * (b.X - center.X) + (b.Y - center.Y) * (b.Y - center.Y);
return d1 > d2;
}


posted on 2021-02-20 15:52  kingBook  阅读(28)  评论(0编辑  收藏