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> Unreal Engine API Reference > Plugins > DynamicMesh > FGroupTopology

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FGroupTopology

Given a per-triangle integer ("group"), [FGroupTopology](API\Plugins\DynamicMesh\FGroupTopology) extracts a group-level topological graph from an input Mesh.

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Inheritance Hierarchy

FGroupTopology

	FTriangleGroupTopology
	FUVGroupTopology

References

Module	DynamicMesh
Header	/Engine/Plugins/Experimental/GeometryProcessing/Source/DynamicMesh/Public/GroupTopology.h
Include	#include "GroupTopology.h"

Syntax

class FGroupTopology

Remarks

Given a per-triangle integer ("group"), FGroupTopology extracts a group-level topological graph from an input Mesh. The graph consists of three elements: Corners: there is a corner at each vertex where 3 or more groups meet (ie 3 or more groups in one-ring) Edges: a group edge is a list of one or more connected edges that have the same pair of different groups on either side Group: a group is a set of connected faces with the same GroupID

By default, the triangle group attribute of the input Mesh is used. You can override GetGroupID to provide your own grouping.

Various query functions are provided to allow group topology to be interrogated. Note that these functions refer to "GroupID", "CornerID", and "GroupEdgeID", these are simply indices into the internal .Groups, .Corners, and .Edges arrays

Variables

	Name	Description
TArray< FCorner...	Corners	List of Corners in the topology graph (ie these are the nodes/vertices of the graph)
TBitArray	CornerVerticesFlags
TArray< FGroupE...	Edges	List of Edges in the topology graph (each edge connects two corners/nodes)
TArray< int >	EmptyArray
TArray< int >	GroupIDToGroupIndexMap
TArray< FGroup ...	Groups	List of Groups in the topology graph (ie faces)
const FDynamicM...	Mesh
TMap< int32, in...	VertexIDToCornerIDMap

Constructors

	Name	Description
	FGroupTopology()
	FGroupTopology ( const FDynamicMesh3* Mesh, bool bAutoBuild )

Destructors

	Name	Description
	~FGroupTopology()

Functions

	Name	Description
void	CollectGroupBoundaryVertices ( int GroupID, TSet< int >& Vertices )	Add all the group boundary vertices of the given GroupID to the Vertices set
void	CollectGroupVertices ( int GroupID, TSet< int >& Vertices )	Add all the vertices of the given GroupID to the Vertices set
void	ExtractGroupEdges ( FGroup& Group )
void	FindCornerNbrGroups ( int CornerID, TArray< int >& GroupsOut )	Add all the groups connected to the given Corner to the GroupsOut list
void	FindCornerNbrGroups ( const TArray< int >& CornerIDs, TArray< int >& GroupsOut )	Add all the groups connected to the given Corners to the GroupsOut list
void	FindEdgeNbrGroups ( int GroupEdgeID, TArray< int >& GroupsOut )	Add the groups connected to the given GroupEdgeID to the GroupsOut list.
void	FindEdgeNbrGroups ( const TArray< int >& GroupEdgeIDs, TArray< int >& GroupsOut )	Add the groups connected to all the GroupEdgeIDs to the GroupsOut list.
int	FindExistingGroupEdge ( int GroupID, int OtherGroupID, int FirstVertexID )
const FGroup...	FindGroupByID ( int GroupID )
int	FindGroupEdgeID ( int MeshEdgeID )
void	FindVertexNbrGroups ( const TArray< int >& VertexIDs, TArray< int >& GroupsOut )	Add all the groups connected to the given Mesh Vertices to the GroupsOut list
void	FindVertexNbrGroups ( int VertexID, TArray< int >& GroupsOut )	Add all the groups connected to the given Mesh Vertex to the GroupsOut list
void	ForGroupEdges ( int GroupID, const TFunction< void... )	Call EdgeFunc for each boundary edge of the given Group (no order defined)
void	ForGroupSetEdges ( const TArray< int >& GroupIDs, const TFunction< void... )	Call EdgeFunc for each boundary edge of each of the given Groups (no order defined)
void	GetAllVertexGroups ( int32 VertexID, TArray< int32 >& GroupsOut )
int32	GetCornerIDFromVertexID ( int32 VertexID )
int	GetCornerVertexID ( int CornerID )
double	GetEdgeArcLength ( int32 GroupEdgeID, TArray< double >* PerVertexLen... )
FVector3d	GetEdgeMidpoint ( int32 GroupEdgeID, double* ArcLengthOut, TArray< double >* PerVertexLen... )
const TArray...	GetGroupEdgeEdges ( int GroupEdgeID )
bool	GetGroupEdgeTangent ( int GroupEdgeID, FVector3d& TangentOut )	Calculate tangent of group edge, as direction from start to end endpoints
const TArray...	GetGroupEdgeVertices ( int GroupEdgeID )
const TArray...	GetGroupFaces ( int GroupID )
FFrame3d	GetGroupFrame ( int32 GroupID )
int	GetGroupID ( int TriangleID )	Adjacency of Per-Triangle integers are what define the triangle groups.
const TArray...	GetGroupNbrGroups ( int GroupID )
const TArray...	GetGroupTriangles ( int GroupID )
void	GetSelectedTriangles ( const FGroupTopologySelection& Sel..., TArray< int32 >& Triangles )	Get the set of selected triangles for a given GroupTopologySelection
FFrame3d	GetSelectionFrame ( const FGroupTopologySelection& Sel..., FFrame3d* InitialLocalFrame )
bool	IsBoundaryEdge ( int32 GroupEdgeID )
bool	IsCornerVertex ( int VertexID )
bool	IsIsolatedLoop ( int32 GroupEdgeID )
bool	IsSimpleGroupEdge ( int32 GroupEdgeID )
FIndex2i	MakeEdgeID ( int MeshEdgeID )
FIndex2i	MakeEdgeID ( int Group1, int Group2 )
void	RebuildTopology()	Build the group topology graph.

Classes

	Name	Description
	FCorner	FCorner is a "corner" in the group topology, IE a vertex where 3+ groups meet.
	FGroup	FGroup is a set of connected triangles with the same GroupID
	FGroupBoundary	A Group is bounded by closed loops of FGroupEdge elements.
	FGroupEdge	FGroupEdge is a sequence of group-boundary-edges where the two groups on either side of each edge are the same.

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