转载自：http://www.cnblogs.com/milian/p/3315000.html
求中点坐标:
/// <summary>
/// 中点
/// </summary>
/// <param name="StartPoint">起点</param>
/// <param name="EndPoint">终点</param>
/// <returns></returns>
public Point3d Midpoint(Point3d StartPoint, Point3d EndPoint)
{
Double x = (StartPoint.X + EndPoint.X)/2;
Double y = (StartPoint.Y + EndPoint.Y) / 2;
Double z = (StartPoint.Z + EndPoint.Z) / 2;
return new Point3d(x, y, z);
}
求点到直线的距离：
/// <summary>
/// 获得空间点到空间线段的垂直距离
/// </summary>
/// <param name="line">直线</param>
/// <param name="pt">空间的点</param>
/// <param name="Decimal">小数位数</param>
/// <returns>点到直线垂直距离</returns>
public Double Distance(Line line, Point3d pt, Int16 Decimal)
{
Double t;
if (line != null)
{
Point3d StartPoint = line.StartPoint;
Point3d EndPoint = line.EndPoint;
//直线方向向量
Point3d dir = new Point3d(StartPoint.X - EndPoint.X, StartPoint.Y - EndPoint.Y, StartPoint.Z - EndPoint.Z);
//过点且与直线垂直的平面
t = -(Double)(dir.X * (StartPoint.X - pt.X) + dir.Y * (StartPoint.Y - pt.Y) + dir.Z * (StartPoint.Z - pt.Z)) / (dir.X * dir.X + dir.Y * dir.Y + dir.Z * dir.Z);
//过点的垂直于直线的平面与该直线的交点
Point3d fp = new Point3d(StartPoint.X + dir.X * t, StartPoint.Y + dir.Y * t, StartPoint.Z + dir.Z * t);
return Distance(pt, fp, Decimal);
}
else
{
return 0;
}
}
求空间两点之间距离：
/// <summary>
/// 空间两点之间距离
/// </summary>
/// <param name="point1">点1</param>
/// <param name="point2">点2</param>
/// <param name="Decimal">小数位数</param>
/// <returns></returns>
public Double Distance(Point3d point1, Point3d point2, Int16 Decimal)
{
Double a = point1.X - point2.X;
Double b = point1.Y - point2.Y;
Double c = point1.Z - point2.Z;
Double r = a * a + b * b + c * c;
return Math.Round(Math.Abs(Math.Sqrt(r)), Decimal);
}
判断两条直线是否重合:
/// <summary>
/// 判断两条直线是否重合
/// </summary>
/// <param name="line1">线1</param>
/// <param name="line2">线2</param>
/// <param name="allowance">容差</param>
/// <returns></returns>
public Boolean Coincide(Line line1, Line line2, Double allowance)
{
LineSegment3d l1 = new LineSegment3d(line1.StartPoint, line1.EndPoint);
LineSegment3d l2 = new LineSegment3d(line2.StartPoint, line2.EndPoint);
Tolerance tol = new Tolerance(allowance, allowance);
return l1.IsColinearTo(l2, tol);
}
判断点是否在直线上:
/// <summary>
/// 判断点是否在直线上
/// </summary>
/// <param name="line">直线</param>
/// <param name="point1">点</param>
/// <param name="allowance">容差</param>
/// <returns></returns>
public Boolean Coincide(Line line, Point3d point1, Double allowance)
{
Point3d p1 = line.StartPoint;
Point3d p2 = line.EndPoint;
//叉积是否为allowance，判断是否在同一直线上
if (Math.Abs((p1.X - point1.X) * (p2.Y - point1.Y) - (p2.X - point1.X) * (p1.Y - point1.Y)) < allowance)
{
return true;
}
else
{
return false;
}
}
判断点是否重合:
/// <summary>
/// 判断点是否重合
/// </summary>
/// <param name="p1">点1</param>
/// <param name="p2">点2</param>
/// <param name="allowance">容差</param>
/// <returns></returns>
public Boolean Coincide(Point3d p1, Point3d p2, Double allowance)
{
if (p1.DistanceTo(p2) < allowance)
return true;
else
return false;
}