Curve Loop Class

System Object
Autodesk.Revit.DB CurveLoop

	Name	Description
	CurveLoop	Constructs a new empty curve loop.

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	Name	Description
	IsValidObject	Specifies whether the .NET object represents a valid Revit entity.

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	Name	Description
	Append	Append the curve to this loop.
	Create
	CreateViaCopy	Creates a new curve loop as a copy of the input.
	CreateViaOffset(CurveLoop, IList Double , XYZ)
	CreateViaOffset(CurveLoop, Double, XYZ)	Creates a new curve loop that is an offset of the existing curve loop.
	CreateViaThicken(Curve, Double, XYZ)	Creates a new closed curve loop by thickening the input curve with respect to a given plane.
	CreateViaThicken(CurveLoop, Double, XYZ)	Creates a new closed curve loop by thickening the input open curve loop with respect to a given plane.
	CreateViaTransform	Creates a new curve loop as a transformed copy of the input curve loop.
	Dispose	Releases all resources used by the CurveLoop
	Equals	Determines whether the specified object is equal to the current object. (Inherited from Object )
	Flip	Reverses the orientation of the curve loop.
	GetBasicIEnumerator	Returns an enumerator that iterates through a collection.
	GetCurveLoopIterator	Returns a curve that iterates through the curve loop.
	GetEnumerator	Returns an enumerator that iterates through a collection.
	GetExactLength	Returns the sum of exact lengths of all curves in the loop.
	GetHashCode	Serves as the default hash function. (Inherited from Object )
	GetPlane	Gets the plane of the curve loop, if it is planar.
	GetRectangularHeight	Returns the width of a curve loop if it is rectangular with respect to the projection plane.
	GetRectangularWidth	Returns the width of a curve loop if it is rectangular with respect to the projection plane.
	GetType	Gets the Type of the current instance. (Inherited from Object )
	HasPlane	Identifies if the CurveLoop is planar.
	IsCounterclockwise	Determines if this CurveLoop is oriented counter-clockwise (CCW) or clockwise (CW) with respect to the specified 3D direction.
	IsOpen	Returns whether the curve loop is open or closed, as determined by an internal flag.
	IsRectangular	Identifies if the curve loop is rectangular with respect to a given projection plane.
	NumberOfCurves	Returns the number of curves in the curve loop.
	ToString	Returns a string that represents the current object. (Inherited from Object )
	Transform	Transforms this curve loop and all of its component curves by the supplied transformation.

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There are specific requirements for how valid CurveLoops must be formed:

• The curves should typically be contiguous.
• The CurveLoop 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.

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