CurveLoop

Description:
A class that represents a chain of curves.

Remarks:
There are a specific set of requirements for how valid CurveLoops must be formed:

The curves must typically be continuous.
It may be either closed (where the start and end points coincide) or open.
There should be no self-intersections.

A CurveLoop is said to be "continuous" if either:

the loop contains at most one curve
the end of each curve coincides with the start of the next one (if there is a next curve).

Many geometry utilities require CurveLoops to be continuous, but discontinuous CurveLoops are sometimes used. For example, the curves in a continuous CurveLoop may be offset, resulting in a discontinuous loop if the offset curves overlap or do not meet, and the offset curves might then be extended or trimmed to form a continuous CurveLoop.

A CurveLoop is said to be "closed" if it is non-empty, continuous, and if either:

the loop contains just one curve, which is unbounded and periodic
the loop's end point coincides with its start point

For example, a CurveLoop comprising four lines forming a rectangle, listed in order around the rectangle, with each curve oriented in direction in which the curves are listed is closed. As another example, a CurveLoop consisting of just one unbounded circle is closed.

A CurveLoop is said to be "open" if it is not closed. For example, a CurveLoop consisting of a single line is open, as is the "offset CurveLoop" mentioned above. Note that an open CurveLoop may be continuous or discontinuous, and a continuous CurveLoop may be open or closed. The definitions imply that a discontinuous CurveLoop is necessarily open and an empty CurveLoop is open.

It should also be noted that these definitions take the order of the curves and the curves' directions into account. For example, a CurveLoop comprising the four edges of a rectangle in the order {bottom, top, left, right} is discontinuous. Similarly, a CurveLoop comprising the four edges of a rectangle in the order {bottom, right, top, left}, with three of the lines oriented in the counter-clockwise direction of the rectangle and the fourth oriented in the clockwise direction, is discontinuous.

Finally, note that some routines in Revit may set the CurveLoop to be marked "open" or "closed" in spite of the actual geometry of the curves. In these special cases, the CurveLoop class does not require that the CurveLoop is correctly marked.

In the API, the members of the CurveLoop may be directly iterated, as the class implements IEnumerable<Curve>. The iteration provides copies of the curves directly contained in the loop; modification of the curves will not affect the curves that are contained in the loop.

Inheritance Hierarchy:
System.Object
Autodesk.Revit.DB.CurveLoop

public class CurveLoop : IEnumerable<Curve>, 
	IDisposable

Public Class CurveLoop _
	Implements IEnumerable(Of Curve), IDisposable

public ref class CurveLoop : IEnumerable<Curve^>, 
	IDisposable

Name	Return Type	Description
C CurveLoop()	None	Constructs a new empty curve loop.

Name	Return Type	Description
M Append(Curve)	None	Append the curve to this loop.
M Create(IList<Curve>)	The curve loop.	Creates a new curve loop.
M CreateViaCopy(CurveLoop)	CurveLoop	Creates a new curve loop as a copy of the input.
M CreateViaOffset(CurveLoop, Double, XYZ)	CurveLoop	Creates a new curve loop that is an offset of the existing curve loop.
M CreateViaOffset(CurveLoop, IList<Double>, XYZ)	CurveLoop	Creates a new curve loop that is an offset of the existing curve loop.
M CreateViaThicken(Curve, Double, XYZ)	CurveLoop	Creates a new closed curve loop by thickening the input curve with respect to a given plane.
M CreateViaThicken(CurveLoop, Double, XYZ)	CurveLoop	Creates a new closed curve loop by thickening the input open curve loop with respect to a given plane.
M CreateViaTransform(CurveLoop, Transform)	CurveLoop	Creates a new curve loop as a transformed copy of the input curve loop.
M Dispose()	None	Releases all resources used by the
M Flip()	None	Reverses the orientation of the curve loop.
M GetBasicIEnumerator()	IEnumerator	Returns an enumerator that iterates through a collection.
M GetCurveLoopIterator()	CurveLoopIterator	Returns a curve that iterates through the curve loop.
M GetEnumerator()	IEnumerator<Curve>	Returns an enumerator that iterates through a collection.
M GetExactLength()	double	Returns the sum of exact lengths of all curves in the loop.
M GetPlane()	Plane	Gets the plane of the curve loop, if it is planar.
M GetRectangularHeight(Plane)	The height.	Returns the width of a curve loop if it is rectangular with respect to the projection plane.
M GetRectangularWidth(Plane)	The width.	Returns the width of a curve loop if it is rectangular with respect to the projection plane.
M HasPlane()	bool	Identifies if the CurveLoop is planar.
M IsCounterclockwise(XYZ)	bool	Determines if this CurveLoop is oriented counter-clockwise (CCW) or clockwise (CW) with respect to the specified 3D direction.
M IsOpen()	bool	Returns whether the curve loop is open or closed, as determined by an internal flag.
M IsRectangular(Plane)	bool	Identifies if the curve loop is rectangular with respect to a given projection plane.
M NumberOfCurves()	int	Returns the number of curves in the curve loop.
M Transform(Transform)	None	Transforms this curve loop and all of its component curves by the supplied transformation.

Name	Return Type	Description
P IsValidObject	bool	Specifies whether the .NET object represents a valid Revit entity.