HalfEdgeList

References
public class HalfEdgeList : IEnumerable<HalfEdge>
Provides access to the halfedges and HalfEdge related functionality of a Mesh. Derived from Plankton, (c) 2013 Daniel Piker and Will Pearson, licensed LGPL v3 or later.

Properties

Count

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public int Count { get; }
Gets the number of halfedges.

Indexers

this[]

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public HalfEdge this[int index] { get; }
Returns the HalfEdge at the given index.
Parameters:
index (int)Index of halfedge to get. Must be larger than or equal to zero and smaller than the Halfedge Count of the mesh.
Returns: The halfedge at the given index.

Methods

Add

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public int Add(HalfEdge halfedge)
Adds a new halfedge to the end of the Halfedge list.
Parameters:
halfedge (HalfEdge)Halfedge to add.
Returns: The index of the newly added halfedge.

CollapseEdge

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public int CollapseEdge(int index)
Collapse an edge by combining 2 vertices
Parameters:
index (int)The index of a halfedge in the edge to collapse. The end vertex will be removed
Returns: The successor to index around its vertex, or -1 on failure.

EndVertex

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public int EndVertex(int halfedgeIndex)
Gets the index of the vertex at the end of a halfedge.
Remarks: This helper actually returns the start vertex of the other halfedge in the pair.
Parameters:
halfedgeIndex (int)The index of a halfedge.
Returns: The index of vertex at the end of the specified halfedge.

FindHalfedge

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public int FindHalfedge(int start, int end)
Gets the halfedge index between two vertices.
Parameters:
start (int)A vertex index.
end (int)A vertex index.
Returns: If it exists, the index of the halfedge which originates from start and terminates at end. Otherwise -1 is returned.

FlipEdge

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public bool FlipEdge(int index)
Performs an edge flip. This works by shifting the start/end vertices of the edge anticlockwise around their faces (by one vertex) and as such can be applied to any n-gon mesh, not just triangulations.
Parameters:
index (int)The index of a halfedge in the edge to be flipped.
Returns: True on success, otherwise false.

GetEnumerator

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public IEnumerator<HalfEdge> GetEnumerator()
Gets an enumerator that yields all halfedges in this collection.
Returns: An enumerator.

GetFaceCirculator

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public IEnumerable<int> GetFaceCirculator(int halfedgeIndex)
Traverses anticlockwise around the adjacent face of a halfedge.
Remarks: Lazily evaluated so if you change the mesh topology whilst using this circulator, you'll know about it!
Parameters:
halfedgeIndex (int)The index of a halfedge.
Returns: An enumerable of halfedge indices incident to the adjacent face of halfedgeIndex. Ordered anticlockwise around the face.

GetLength

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public double GetLength(int index)
Measure the length of a single halfedge
Parameters:
index (int)
Returns: The length of the halfedge, or -1 if unused

GetLengths

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public double[] GetLengths()
Measure the lengths of all the halfedges
Returns: An array of lengths for all halfedges, or -1 for dead ones

GetNextHalfEdge

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public int GetNextHalfEdge(int startHalfEdge, int around)
obsoleteGetNextHalfedge(int,int) is deprecated, please useGetFaceCirculator(int).ElementAt(int) instead (LINQ).
Gets the halfedge a given number of 'next's around a face from a starting halfedge
Parameters:
startHalfEdge (int)The halfedge to start from
around (int)How many steps around the face. 0 returns the start_he
Returns: The resulting halfedge

GetPairHalfedge

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public int GetPairHalfedge(int halfedgeIndex)
Gets the opposing halfedge in a pair.
Parameters:
halfedgeIndex (int)A halfedge index.
Returns: The halfedge index with which the specified halfedge is paired.

GetVertexCirculator

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public IEnumerable<int> GetVertexCirculator(int halfedgeIndex)
Traverses clockwise around the starting vertex of a halfedge.
Remarks: Lazily evaluated so if you change the mesh topology whilst using this circulator, you'll know about it!
Parameters:
halfedgeIndex (int)The index of a halfedge.
Returns: An enumerable of halfedge indices incident to the starting vertex of halfedgeIndex. Ordered clockwise around the vertex. The returned enumerable will start with the specified halfedge.

GetVertices

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public int[] GetVertices(int index)
Gets the two vertices for a halfedge.
Parameters:
index (int)A halfedge index.
Returns: The pair of vertex indices connected by the specified halfedge. The order follows the direction of the halfedge.

IsBoundary

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public bool IsBoundary(int index)
A halfedge is on a boundary if it only has a face on one side.
Parameters:
index (int)The index of a halfedge.
Returns: true if the specified halfedge is on a boundary; otherwise, false.

PairHalfedge

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public int PairHalfedge(int halfedgeIndex)
obsoletePairHalfedge is deprecated, pease use GetPairHalfedge instead.
Parameters:
halfedgeIndex (int)

PinchOff

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public bool PinchOff(int index)
Given a halfedge which is on the boundary at each end, but is not a boundary edge itself separate the mesh here by flipping edges so 2 faces can be removed without changing vertex count
Parameters:
index (int)The index of a halfedge in the edge to pinch
Returns: True on success, otherwise false.

SplitEdge

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public int SplitEdge(int index)
Creates a new vertex, and inserts it along an existing edge, splitting it in 2.
Parameters:
index (int)The index of a halfedge in the edge to be split.
Returns: The index of the newly created halfedge in the same direction as the input halfedge.
Explicit

IEnumerable.GetEnumerator

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IEnumerator IEnumerable.GetEnumerator()

TriangleSplitEdge

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public int TriangleSplitEdge(int index)
Split 2 adjacent triangles into 4 by inserting a new vertex along the edge
Parameters:
index (int)The index of the halfedge to split. Must be between 2 triangles.
Returns: The index of the halfedge going from the new vertex to the end of the input halfedge, or -1 on failure