Autodesk.Revit.DB.PointOnPlane是Revit API中的类，用于表示平面上的一个点。
// 创建一个新的PointOnPlane对象
Plane plane = new Plane(new XYZ(0, 0, 1), new XYZ(0, 0, 0));
XYZ point = new XYZ(1, 2, 0);
PointOnPlane pointOnPlane = new PointOnPlane(plane, point);
// 使用DistanceTo方法计算两个点之间的距离
XYZ anotherPoint = new XYZ(3, 4, 0);
double distance = pointOnPlane.DistanceTo(anotherPoint);
// 使用IsAlmostEqualTo方法判断两个点是否几乎相等
PointOnPlane anotherPointOnPlane = new PointOnPlane(plane, anotherPoint);
bool isAlmostEqual = pointOnPlane.IsAlmostEqualTo(anotherPointOnPlane);