FMeshPlaneCut | Unreal Engine 5.0 Documentation

API > API/Plugins > API/Plugins/DynamicMesh > API/Plugins/DynamicMesh/Operations

References


Module	DynamicMesh
Header	/Engine/Plugins/Runtime/GeometryProcessing/Source/DynamicMesh/Public/Operations/MeshPlaneCut.h
Include	#include "Operations/MeshPlaneCut.h"

Syntax

class FMeshPlaneCut

Remarks

Cut the Mesh with the Plane. The positive side, ie (p-o).n > 0, is removed. If possible, returns boundary loop(s) along cut (this will fail if cut intersected with holes in mesh). Also FillHoles() for a topological fill. Or use CutLoops and fill yourself.

Algorithm is: 1) find all edge crossings 2) optionally discard any triangles with all vertex distances < epsilon. 3) Do edge splits at crossings 4 option a) (optionally) delete all vertices on positive side 4 option b) (OR optionally) disconnect all triangles w/ vertices on positive side (if keeping both sides) 4 option c) do nothing (if keeping both sides and not disconnecting them) 5) (optionally) collapse any degenerate boundary edges 6) (optionally) change an attribute tag for all triangles on positive side 7) find loops through valid boundary edges (ie connected to splits, or on-plane edges) (if second half was kept, do this separately for each separate mesh ID label)

Variables

Type	Name	Description
bool	bCollapseDegenerateEdgesOnCut
bool	bSimplifyAlongNewEdges	Control whether we attempt to auto-simplify the small planar triangles that the plane cut operation tends to generate
double	DegenerateEdgeTol
TUniqueFunction< bool(int32)>	EdgeFilterFunc	If set, only edges that pass this filter will be split
TArray< TArray< int > >	HoleFillTriangles	Triangle IDs of hole fill triangles. Outer array is 1:1 with the OpenBoundaries array.
FDynamicMesh3 *	Mesh	Inputs
TArray< FOpenBoundary >	OpenBoundaries	Note: loops and spans within a single FOpenBoundary could be part of the same hole-fill triangulation separate open boundary structs will be considered separately and will not share hole fill triangles
FVector3d	PlaneNormal
FVector3d	PlaneOrigin
double	PlaneTolerance	Tolerance distance for considering a vertex to be 'on plane'
TArray< FCutResultRegion >	ResultRegions	List of output cut regions (eg that have separate GroupIDs).
FLocalPlanarSimplify	SimplifySettings	Settings to apply if bSimplifyAlongNewEdges == true
float	UVScaleFactor	UVs on any hole fill surfaces are scaled by this amount

Constructors

	Type	Name	Description
		FMeshPlaneCut ( FDynamicMesh3* Mesh, FVector3d Origin, FVector3d Normal )	Cut mesh with plane. Assumption is that plane normal is Z value.

Destructors

	Type	Name	Description
	PRAGMA_DISABLE_DEPRECATION_WARNINGS	~FMeshPlaneCut ()	Note: deprecation warnings disabled on destructor due to deprecated member variables.

Functions

Type	Name	Description
void	CollapseDegenerateEdges ( TSet< int >& Edges, bool bRemoveAllDegenerateFromInputSet, TSet< int >* TriangleSelection )	Collapse degenerate edges
bool	Cut ()	Compute the plane cut by splitting mesh edges that cross the cut plane, and then deleting any triangles on the positive side of the cutting plane.
bool	CutWithoutDelete ( bool bSplitVerticesAtPlane, float OffsetSeparatedPortion, TDynamicMeshScalarTriangleAttribute< int >* TriLabels, int NewLabelStartID, bool bAddBoundariesFirstHalf, bool bAddBoundariesSecondHalf )	Compute the plane cut by splitting mesh edges that cross the cut plane, but not deleting triangles on positive side.
bool	ExtractBoundaryLoops ( const TSet< int >& OnCutEdges, const TSet< int >& ZeroEdges, FMeshPlaneCut::FOpenBoundary& Boundary )
bool	HoleFill ( TFunction< TArray< FIndex3i >(const FGeneralPolygon2d&)> PlanarTriangulationFunc, bool bFillSpans, int ConstantGroupID )	Fill cut loops with FPlanarHoleFiller, using a caller-provided triangulation function
bool	MinimalHoleFill ( int ConstantGroupID )
bool	SimpleHoleFill ( int ConstantGroupID )	Fill cut loops with FSimpleHoleFiller
void	SplitCrossingEdges ( bool bDeleteTrisOnPlane, TArray< double >& Signs, TSet< int >& AlreadyOnPlaneEdges, TSet< int32 >& CutPlaneEdges, TSet< int >* SplitEdges, TSet< int >* OnPlaneVertices, TSet< int >* TriangleSelection )
void	SplitCrossingEdges ( TArray< double >& Signs, TSet< int >& ZeroEdges, TSet< int >& OnCutEdges, TSet< int >& OnSplitEdges, bool bDeleteTrisOnPlane )
void	SplitCrossingEdges ( TArray< double >& Signs, TSet< int >& ZeroEdges, TSet< int >& OnCutEdges, bool bDeleteTrisOnPlane )
bool	SplitEdgesOnly ( bool bAssignNewGroups, TSet< int32 >* OptionalTriangleSelection )	Compute the plane cut by splitting mesh edges that cross the cut plane, and then optionally update groups
void	TransferTriangleLabelsToHoleFillTriangles ( TDynamicMeshScalarTriangleAttribute< int >* TriLabels )
EOperationValidationResult	Validate ()

Classes

	Type	Name	Description
	FCutResultRegion
	FOpenBoundary	TODO support optionally restricting plane cut to a mesh selection MeshFaceSelection CutFaceSet; Outputs

Deprecated Variables

	Type	Name	Description
	TSet< int32 >	OnCutVertices	If needed, explicitly request the vertices on the cut plane the the OnPlaneVertices argument of SplitCrossingEdges
	PRAGMA_DISABLE_DEPRECATION_WARNINGS TArray< int32 >	ResultSeedTriangles	To preserve a triangle selection when using SplitEdgesOnly(), instead pass the selection as a pointer to that function.

Deprecated Functions

	Type	Name	Description
	void	CollapseDegenerateEdges ( const TSet< int >& OnCutEdges, const TSet< int >& ZeroEdges )	Use the single-set CollapseDegenerateEdges instead
	bool	SplitEdgesOnly ( bool bAssignNewGroups )	Instead use the two-parameter version of SplitEdgesOnly, which has direction selection tracking and does not populate the deprecated ResultSeedTriangles

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