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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

Inheritance Hierarchy

References

   
Module DynamicMesh
Header /Engine/Plugins/Runtime/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 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).

Variables

  Type Name Description
Public variable TArray< FCorner > Corners List of Corners in the topology graph (ie these are the nodes/vertices of the graph)
Protected variable TSet< int32 > CurrentExtraCornerVids  
Public variable TArray< FGroupEdge > Edges List of Edges in the topology graph (each edge connects two corners/nodes)
Protected variable TArray< int > EmptyArray  
Protected variable TArray< int > GroupIDToGroupIndexMap  
Protected variable const FDynamicMeshPolygroupAttribute * GroupLayer  
Public variable TArray< FGroup > Groups List of Groups in the topology graph (ie faces)
Protected variable const FDynamicMesh3 * Mesh  
Public variable   PRAGMA_DISABLE_DEPRECATION_WARNINGS  
Public variable TFunction< bool(const FGroupTopology &GroupTopology, int32 Vid, const FIndex2i &AttachedGroupEdgeEid... ShouldAddExtraCornerAtVert 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.
Protected variable TMap< int32, int32 > VertexIDToCornerIDMap  

Constructors

  Type Name Description
Public function    
Public function    
Public function  

FGroupTopology ( const FDynamicMesh3* Mesh,
bool bAutoBuild
)

  
Public function  

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

  

Destructors

  Type Name Description
Public function Virtual    

Functions

  Type Name Description
Public function Const void

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

 Add all the group boundary vertices of the given GroupID to the Vertices set
Public function Const void

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

 Add all the vertices of the given GroupID to the Vertices set
Public function Const void

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

 Add all the Corners connected to the given Corner to the EdgesOut list.
Public function Const void

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

 Add all the Edges connected to the given Corner to the EdgesOut list.
Public function Const void

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

 Add all the groups connected to the given Corners to the GroupsOut list
Public function Const void

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

 Add all the groups connected to the given Corner to the GroupsOut list
Public function Const void

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

 Add the edges connected to the given GroupEdgeID to the EdgesOut list. This is somewhat expensive.
Public function Const void

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

 Add the groups connected to all the GroupEdgeIDs to the GroupsOut list.
Public function Const void

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

 Add the groups connected to the given GroupEdgeID to the GroupsOut list.
Public function Const const FGroup *

FindGroupByID ( int GroupID
)

  
Public function Const int

FindGroupEdgeID ( int MeshEdgeID
)

  
Public function Const int

FindGroupEdgeID ( FMeshTriEdgeID FMeshTriEdgeID
)

  
Public function Const void

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

 Add all the groups connected to the given Mesh Vertex to the GroupsOut list
Public function Const void

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

 Add all the groups connected to the given Mesh Vertices to the GroupsOut list
Public function Const void

ForGroupEdges ( int GroupID,
const FuncTakingFGroupEdgeAndInt& EdgeFunc
)

 Call EdgeFunc for each boundary edge of the given Group (no order defined).
Public function Const void

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

 Call EdgeFunc for each boundary edge of each of the given Groups (no order defined).
Protected function 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.
Protected function Const void

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

  
Public function Const int32

GetCornerIDFromVertexID ( int32 VertexID
)

  
Public function Const int

GetCornerVertexID ( int CornerID
)

  
Public function Const const TSet< int32 > &  
Public function Const double

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

  
Public function Const FVector3d

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

  
Public function Const const TArray< int > &

GetGroupEdgeEdges ( int GroupEdgeID
)

  
Public function Const bool

GetGroupEdgeTangent ( int GroupEdgeID,
FVector3d& TangentOut
)

 Calculate tangent of group edge, as direction from start to end endpoints
Public function Const const TArray< int > &

GetGroupEdgeVertices ( int GroupEdgeID
)

  
Public function Const const TArray< int > &

GetGroupFaces ( int GroupID
)

  
Public function Const FFrame3d

GetGroupFrame ( int32 GroupID
)

  
Public function Virtual Const int

GetGroupID ( int TriangleID
)

 Adjacency of Per-Triangle integers are what define the triangle groups.
Public function Const const TArray< int > &

GetGroupNbrGroups ( int GroupID
)

  
Public function Const const TArray< int > &

GetGroupTriangles ( int GroupID
)

  
Public function Const const FDynamicMesh3 *

GetMesh ()

  
Public function Const void

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

 Get the set of selected triangles for a given GroupTopologySelection
Public function Const FAxisAlignedBox3d

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

  
Public function Const FFrame3d

GetSelectionFrame ( const FGroupTopologySelection& Selection,
FFrame3d* InitialLocalFrame
)

  
Public function Const bool

IsBoundaryEdge ( int32 GroupEdgeID
)

  
Public function Static bool

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

 Helper function for use with ShouldAddExtraCornerAtVert.
Public function Const bool

IsGroupEdge ( FMeshTriEdgeID TriEdgeID,
bool bIncludeMeshBoundary
)

  
Public function Const bool

IsIsolatedLoop ( int32 GroupEdgeID
)

  
Public function Const bool

IsSimpleGroupEdge ( int32 GroupEdgeID
)

  
Protected function Const FIndex2i

MakeEdgeGroupsPair ( int MeshEdgeID
)

  
Protected function Const FIndex2i

MakeEdgeGroupsPair ( int Group1,
int Group2
)

  
Public function Virtual bool Build the group topology graph.
Public function 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.
Public function void Keeps the structures of topology in place but points the mesh pointers to a new cloned mesh.
Protected function Virtual Const bool

ShouldVertBeCorner ( int VertexID,
bool* bIsExtraCornerOut
)

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

Operators

  Type Name Description
Public function FGroupTopology &  

Classes

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

Deprecated Variables

  Type Name Description
Protected variable TBitArray CornerVerticesFlags Use VertexIDToCornerIDMap instead.

Deprecated Functions

  Type Name Description
Protected function bool Use GenerateBoundaryAndGroupEdges instead.
Protected function int

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

 Group edges cannot be uniquely identified by a group pair.
Protected function Virtual Const bool

IsCornerVertex ( int VertexID
)

 Use ShouldVertBeCorner instead.
Protected function Const FIndex2i

MakeEdgeID ( int MeshEdgeID
)

 Use MakeEdgeGroupsPair instead. The returned pair cannot uniquely identify a group edge.
Protected function Const FIndex2i

MakeEdgeID ( int Group1,
int Group2
)

 Use MakeEdgeGroupsPair instead. The returned pair cannot uniquely identify a group edge.

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