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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.

API > API/Plugins > API/Plugins/DynamicMesh

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 when functions refer to "CornerID", and "GroupEdgeID", these are simply indices into the internal Corners and Edges arrays. However references to "GroupID" refer to the actual group IDs in FDynamicMesh (not an index into Groups).

   
Name FGroupTopology
Type class
Header File /Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/GroupTopology.h
Include Path #include "GroupTopology.h"

Syntax

class FGroupTopology

Derived Classes

Constructors

Name Remarks Include Path Unreal Specifiers

FGroupTopology ( const FDynamicMesh3* Mesh,
bool bAutoBuild
)

   GroupTopology.h  

FGroupTopology ( const FDynamicMesh3* Mesh,
const FDynamicMeshPolygroupAttribute* GroupLayer,
bool bAutoBuild
)

   GroupTopology.h  
  GroupTopology.h  
  GroupTopology.h  

Destructors

Name Remarks Include Path Unreal Specifiers

virtual ~FGroupTopology()

   GroupTopology.h  

Structs

Name Remarks
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.

Variables

Public

Name Type Remarks Include Path Unreal Specifiers
Corners TArray< FCorner > List of Corners in the topology graph (ie these are the nodes/vertices of the graph) GroupTopology.h  
Edges TArray< FGroupEdge > List of Edges in the topology graph (each edge connects two corners/nodes) GroupTopology.h  
Groups TArray< FGroup > List of Groups in the topology graph (ie faces) GroupTopology.h  
PRAGMA_DISABLE_DEPRECATION_WARNINGS     GroupTopology.h  
ShouldAddExtraCornerAtVert TFunction< bool(const FGroupTopology &GroupTopology, int32 Vid, const FIndex2i &AttachedGroupEdgeEids)> Optional function that will add extra corners (in addition to the ones that are always placed at junctures of three or more group edges) during RebuildTopology whenever the function returns true for a vertex that is part of a group edge. GroupTopology.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

void CollectGroupBoundaryVertices ( int GroupID,
TSet< int >& Vertices
) const

 Add all the group boundary vertices of the given GroupID to the Vertices set GroupTopology.h  

void CollectGroupVertices ( int GroupID,
TSet< int >& Vertices
) const

 Add all the vertices of the given GroupID to the Vertices set GroupTopology.h  

void FindCornerNbrCorners ( int CornerID,
TArray< int >& CornersOut
) const

 Add all the Corners connected to the given Corner to the EdgesOut list. GroupTopology.h  

void FindCornerNbrEdges ( int CornerID,
TArray< int >& EdgesOut
) const

 Add all the Edges connected to the given Corner to the EdgesOut list. GroupTopology.h  

void FindCornerNbrGroups ( const TArray< int >& CornerIDs,
TArray< int >& GroupsOut
) const

 Add all the groups connected to the given Corners to the GroupsOut list GroupTopology.h  

void FindCornerNbrGroups ( int CornerID,
TArray< int >& GroupsOut
) const

 Add all the groups connected to the given Corner to the GroupsOut list GroupTopology.h  

void FindEdgeNbrEdges ( int GroupEdgeID,
TArray< int >& EdgesOut
) const

 Add the edges connected to the given GroupEdgeID to the EdgesOut list. This is somewhat expensive. GroupTopology.h  

void FindEdgeNbrGroups ( const TArray< int >& GroupEdgeIDs,
TArray< int >& GroupsOut
) const

 Add the groups connected to all the GroupEdgeIDs to the GroupsOut list. GroupTopology.h  

void FindEdgeNbrGroups ( int GroupEdgeID,
TArray< int >& GroupsOut
) const

 Add the groups connected to the given GroupEdgeID to the GroupsOut list. GroupTopology.h  

const FGroup * FindGroupByID ( int GroupID
) const

   GroupTopology.h  

int FindGroupEdgeID ( int MeshEdgeID
) const

   GroupTopology.h  

int FindGroupEdgeID ( FMeshTriEdgeID FMeshTriEdgeID
) const

   GroupTopology.h  

void FindVertexNbrGroups ( int VertexID,
TArray< int >& GroupsOut
) const

 Add all the groups connected to the given Mesh Vertex to the GroupsOut list GroupTopology.h  

void FindVertexNbrGroups ( const TArray< int >& VertexIDs,
TArray< int >& GroupsOut
) const

 Add all the groups connected to the given Mesh Vertices to the GroupsOut list GroupTopology.h  

void ForCornerNbrEdges ( int CornerID,
TFunctionRef< bool(int32 EdgeID)> ReturnTrueToContinue
) const

 Helper that iterates over the group edges neighboring a particular corner. GroupTopology.h  

void ForGroupEdges ( int GroupID,
const FuncTakingFGroupEdgeAndInt& EdgeFunc
) const

 Call EdgeFunc for each boundary edge of the given Group (no order defined). GroupTopology.h  

void ForGroupSetEdges ( const IntIterableContainerType& GroupIDs,
const FuncTakingFGroupEdgeAndInt& EdgeFunc
) const

 Call EdgeFunc for each boundary edge of each of the given Groups (no order defined). GroupTopology.h  

int32 GetCornerIDFromVertexID ( int32 VertexID
) const

   GroupTopology.h  

int GetCornerVertexID ( int CornerID
) const

   GroupTopology.h  

const TSet< int32 > & GetCurrentExtraCornerVids()

   GroupTopology.h  

double GetEdgeArcLength ( int32 GroupEdgeID,
TArray< double >* PerVertexLengthsOut
) const

   GroupTopology.h  

FVector3d GetEdgeAveragePosition ( int32 GroupEdgeID
) const

   GroupTopology.h  

FVector3d GetEdgeMidpoint ( int32 GroupEdgeID,
double* ArcLengthOut,
TArray< double >* PerVertexLengthsOut
) const

   GroupTopology.h  

const TArray< int > & GetGroupEdgeEdges ( int GroupEdgeID
) const

   GroupTopology.h  

bool GetGroupEdgeTangent ( int GroupEdgeID,
FVector3d& TangentOut
) const

 Calculate tangent of group edge, as direction from start to end endpoints GroupTopology.h  

const TArray< int > & GetGroupEdgeVertices ( int GroupEdgeID
) const

   GroupTopology.h  

const TArray< int > & GetGroupFaces ( int GroupID
) const

   GroupTopology.h  

FFrame3d GetGroupFrame ( int32 GroupID
) const

   GroupTopology.h  

virtual int GetGroupID ( int TriangleID
) const

 Adjacency of Per-Triangle integers are what define the triangle groups. GroupTopology.h  

const TArray< int > & GetGroupNbrGroups ( int GroupID
) const

   GroupTopology.h  

const TArray< int > & GetGroupTriangles ( int GroupID
) const

   GroupTopology.h  

const FDynamicMesh3 * GetMesh()

   GroupTopology.h  

void GetSelectedTriangles ( const FGroupTopologySelection& Selection,
TArray< int32 >& Triangles
) const

 Get the set of selected triangles for a given GroupTopologySelection GroupTopology.h  

FAxisAlignedBox3d GetSelectionBounds ( const FGroupTopologySelection& Selection,
TFunctionRef< FVector3d(const FVector3d&)> TransformFunc
) const

   GroupTopology.h  

FFrame3d GetSelectionFrame ( const FGroupTopologySelection& Selection,
FFrame3d* InitialLocalFrame
) const

   GroupTopology.h  

bool IsBoundaryEdge ( int32 GroupEdgeID
) const

   GroupTopology.h  

bool IsGroupEdge ( FMeshTriEdgeID TriEdgeID,
bool bIncludeMeshBoundary
) const

   GroupTopology.h  

bool IsIsolatedLoop ( int32 GroupEdgeID
) const

   GroupTopology.h  

bool IsSimpleGroupEdge ( int32 GroupEdgeID
) const

   GroupTopology.h  

virtual bool RebuildTopology()

 Build the group topology graph. GroupTopology.h  

virtual bool RebuildTopologyWithSpecificExtraCorners ( const TSet< int32 >& ExtraCornerVids
)

 Rebuilds the topology graph while ignoring ShouldAddExtraCornerAtVert and only determining whether an extra corner should be forced by seeing whether the vertex is in the provided set. GroupTopology.h  

void RetargetOnClonedMesh ( const FDynamicMesh3* Mesh
)

 Keeps the structures of topology in place but points the mesh pointers to a new cloned mesh. GroupTopology.h  

Protected

Name Remarks Include Path Unreal Specifiers

bool ExtractGroupEdges ( FGroup& Group
)

 Return false if we had a problem finding group boundaries GroupTopology.h  

int FindExistingGroupEdge ( int GroupID,
int OtherGroupID,
int FirstVertexID,
int SecondVertexID
)

   GroupTopology.h  

bool GenerateBoundaryAndGroupEdges ( FGroup& Group,
TMap< int32, int32 >& GroupEdgeMinEidToGroupEdgeID,
TBitArray<>& VertCheckedForCorner
)

 Generates group edges and boundary structs for given group. Returns false if failed to find group boundaries. GroupTopology.h  

void GetAllVertexGroups ( int32 VertexID,
TArray< int32 >& GroupsOut
) const

   GroupTopology.h  

virtual bool IsCornerVertex ( int VertexID
) const

   GroupTopology.h  

FIndex2i MakeEdgeGroupsPair ( int Group1,
int Group2
) const

   GroupTopology.h  

FIndex2i MakeEdgeGroupsPair ( int MeshEdgeID
) const

   GroupTopology.h  

FIndex2i MakeEdgeID ( int MeshEdgeID
) const

   GroupTopology.h  

FIndex2i MakeEdgeID ( int Group1,
int Group2
) const

   GroupTopology.h  

virtual bool ShouldVertBeCorner ( int VertexID,
bool* bIsExtraCornerOut
) const

 Return true if the given vertex should be a corner based on the number of adjoining group edges or based on ShouldAddExtraCornerAtVert, if provided. GroupTopology.h  

Static

Name Remarks Include Path Unreal Specifiers

static bool IsEdgeAngleSharp ( const FDynamicMesh3* Mesh,
int32 SharedVid,
const FIndex2i& AttachedGroupEdgeEids,
double DotThreshold
)

 Helper function for use with ShouldAddExtraCornerAtVert. GroupTopology.h  

Operators

Name Remarks Include Path Unreal Specifiers

FGroupTopology & operator= ( const FGroupTopology&
)

   GroupTopology.h  

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