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  3. FArrangement2d

FArrangement2d

Arrangement2d constructs a planar arrangement of a set of 2D line segments.

API > API/Plugins > API/Plugins/GeometryAlgorithms

Arrangement2d constructs a planar arrangement of a set of 2D line segments. When a segment is inserted, existing edges are split, and the inserted segment becomes multiple graph edges. So, the resulting FDynamicGraph2d should not have any edges that intersect.

Calculations are performed in double-precision, so there is no guarantee of correctness.

[TODO] multi-level segment has to accelerate find_intersecting_edges() [TODO] maybe smarter handling

   
Name FArrangement2d
Type struct
Header File /Engine/Plugins/Runtime/GeometryProcessing/Source/GeometryAlgorithms/Public/Arrangement2d.h
Include Path #include "Arrangement2d.h"

Syntax

struct FArrangement2d

Constructors

Name Remarks Include Path Unreal Specifiers

FArrangement2d ( double PointHashCellSize
)

   Arrangement2d.h  

FArrangement2d ( const FAxisAlignedBox2d& BoundsHint
)

   Arrangement2d.h  

Structs

Name Remarks
FIntersection  
FSegmentPoint  

Variables

Public

Name Type Remarks Include Path Unreal Specifiers
Graph FDynamicGraph2d Graph of arrangement Arrangement2d.h  
PointHash TPointHashGrid2d< int > PointHash for vertices of graph. Arrangement2d.h  
VertexSnapTol double Points within this tolerance are merged Arrangement2d.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

bool AttemptTriangulate ( TArray< FIntVector >& Triangles,
TArray< int32 >& SkippedEdges,
int32 BoundaryEdgeGroupID
)

 Variant of AttemptTriangulate using FIntVector instead of FIndex3i; Note this incurs an extra copy of the triangle array Arrangement2d.h  

bool AttemptTriangulate ( TArray< FIndex3i >& Triangles,
TArray< int32 >& SkippedEdges,
int32 BoundaryEdgeGroupID
)

 Attempts to triangulates the arrangement with a constrained Delaunay triangulation NOTE: Will return all triangles if no edges found with the BoundaryEdgeGroupID NOTE: May fail if arrangement has self-intersections Arrangement2d.h  

void ConnectOpenBoundaries ( double DistThresh
)

 Graph improvement connect open boundary vertices within DistThresh, by inserting new segments Arrangement2d.h  

bool HasSelfIntersections()

 Check if current Graph has self-intersections; not optimized, only for debugging Arrangement2d.h  

bool HasVertexNear ( FVector2d Point,
double SearchRadius
)

 Check if vertex exists in region Arrangement2d.h  

void Insert ( const FSegment2d& Segment,
int GID
)

 Insert segment into the arrangement Arrangement2d.h  

int Insert ( const FVector2d& Pt
)

 Insert isolated point P into the arrangement Arrangement2d.h  

void Insert ( const FVector2d& A,
const FVector2d& B,
int GID
)

 Insert segment [A,B] into the arrangement Arrangement2d.h  

void Insert ( const FPolygon2d& Poly,
int GID
)

 Int N = pline.VertexCount - 1; for (int i = 0; i < N; ++i) { FVector2d A = pline[i]; FVector2d B = pline[i + 1]; insert_segment(A, B, GID); } Arrangement2d.h  

int32 InsertNewIsolatedPointUnsafe ( const FVector2d& Pt
)

 Insert isolated point P into the arrangement when you know by construction it's not too close to any vertex or edge Much faster, but will break things if you use it to insert a point that is on top of any existing element! Arrangement2d.h  

FIndex2i SplitEdgeAtPoint ( int EdgeID,
FVector2d Point
)

 Subdivide edge at a given position Arrangement2d.h  

bool Triangulate ( TArray< FIndex3i >& Triangles
)

 Attempts to triangulate the arrangement with a constrained Delaunay triangulation NOTE: May fail if arrangement has self-intersections Arrangement2d.h  

bool TriangulateWithBoundary ( TArray< FIndex3i >& Triangles,
int32 BoundaryEdgeGroupID
)

 Attempts to triangulate the arrangement with a constrained Delaunay triangulation NOTE: May fail if arrangement has self-intersections Arrangement2d.h  

bool TriangulateWithBoundaryAndHoles ( TArray< FIndex3i >& Triangles,
int32 BoundaryEdgeGroupID,
int32 HoleEdgeGroupID
)

 Attempts to triangulate the arrangement with a constrained Delaunay triangulation NOTE: May fail if arrangement has self-intersections Arrangement2d.h  

Protected

Name Remarks Include Path Unreal Specifiers

int find_existing_vertex ( FVector2d Pt
)

 Find existing vertex at point, if it exists Arrangement2d.h  

bool find_intersecting_edges ( FVector2d A,
FVector2d B,
TArray< FIntersection >& Hits,
double Tol
)

 Find set of edges in graph that intersect with edge [A,B] Arrangement2d.h  

bool find_intersecting_floating_vertices ( const FSegment2d& SegAB,
int32 AID,
int32 BID,
TArray< FSegmentPoint >& Hits,
double Tol
)

   Arrangement2d.h  

int find_nearest_boundary_vertex ( FVector2d Pt,
double SearchRadius,
int IgnoreVID
)

 Find nearest boundary vertex, within SearchRadius Arrangement2d.h  

int find_nearest_vertex ( FVector2d Pt,
double SearchRadius,
int IgnoreVID
)

 Find closest vertex, within SearchRadius Arrangement2d.h  

int insert_point ( const FVector2d& P,
double Tol
)

 Insert pt P into the arrangement, splitting existing edges as necessary Arrangement2d.h  

bool insert_segment ( FVector2d A,
FVector2d B,
int GID,
double Tol
)

 Insert edge [A,B] into the arrangement, splitting existing edges as necessary Arrangement2d.h  

FIndex2i split_segment_at_t ( int EID,
double T,
double Tol
)

 Insert new point into segment EID at parameter value T If T is within Tol of endpoint of segment, we use that instead. Arrangement2d.h  

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