#include <LocalPlanarSimplify.h>

Public Member Functions
GEOMETRYCORE_API void	SimplifyAlongEdges (FDynamicMesh3 &Mesh, TSet< int32 > &InOutEdges, TUniqueFunction< void(const DynamicMeshInfo::FEdgeCollapseInfo &)> ProcessCollapse=nullptr) const

Static Public Member Functions
static GEOMETRYCORE_API void	CollapseDegenerateEdges (FDynamicMesh3 &Mesh, TSet< int32 > &InOutEdges, bool bRemoveAllDegenerateFromInputSet=false, double DegenerateEdgeLenTol=UE_DOUBLE_SMALL_NUMBER, TSet< int > *TriangleSelection=nullptr)

static GEOMETRYCORE_API bool	IsFlat (const FDynamicMesh3 &Mesh, int VID, double DotTolerance, FVector3d &OutFirstNormal)

static GEOMETRYCORE_API bool	IsDevelopableAlongEdge (const FDynamicMesh3 &Mesh, int EID, int VID, double DotTolerance, FVector3d &NormalA, bool &bIsFlat)

static GEOMETRYCORE_API bool	CollapseWouldHurtTriangleQuality (const FDynamicMesh3 &Mesh, const FVector3d &RemoveVNormal, int32 RemoveV, const FVector3d &RemoveVPos, int32 KeepV, const FVector3d &KeepVPos, double TryToImproveTriQualityThreshold, bool bHasMultipleNormals=false)

static GEOMETRYCORE_API bool	CollapseWouldChangeShapeOrUVs (const FDynamicMesh3 &Mesh, const TSet< int > &PathEdgeSet, double DotTolerance, int SourceEID, int32 RemoveV, const FVector3d &RemoveVPos, int32 KeepV, const FVector3d &KeepVPos, const FVector3d &EdgeDir, bool bPreserveTriangleGroups, bool bPreserveUVsForMesh, bool bPreserveVertexUVs, bool bPreserveOverlayUVs, float UVToleranceSq, bool bPreserveVertexNormals, float NormalEqualCosThreshold)

Public Attributes
double	SimplificationAngleTolerance = .1

double	TryToImproveTriQualityThreshold = .25

bool	bPreserveTriangleGroups = true

bool	bPreserveVertexUVs = true

bool	bPreserveOverlayUVs = true

float	UVDistortTolerance = FMathf::ZeroTolerance

bool	bPreserveVertexNormals = true

float	NormalDistortTolerance = .01f

Member Function Documentation

◆ CollapseDegenerateEdges()

void FLocalPlanarSimplify::CollapseDegenerateEdges	(	FDynamicMesh3 &	Mesh,
		TSet< int32 > &	InOutEdges,
		bool	bRemoveAllDegenerateFromInputSet = `false`,
		double	DegenerateEdgeLenTol = `UE_DOUBLE_SMALL_NUMBER`,
		TSet< int > *	TriangleSelection = `nullptr`
	)

static

Collapse degenerate edges. Note that SimplifyAlongEdges currently assumes that this (or a similar pass) is run beforehand

Parameters

Mesh	Mesh to repair
InOutEdges	Set of edges to consider for collapse; optionally updated by removing edges at they are collapsed
bRemoveAllDegenerateFromInputSet	Whether we should also check whether the neighbor edges removed by collapse were also in the set. Note: Often not needed, and has additional processing cost.
DegenerateEdgeLenTol	Tolerance length at which we collapse edges
TriangleSelection	Optional set tracking an active selection. Any triangles removed by collapse will also be removed from the set.

◆ CollapseWouldChangeShapeOrUVs()

bool FLocalPlanarSimplify::CollapseWouldChangeShapeOrUVs	(	const FDynamicMesh3 &	Mesh,
		const TSet< int > &	PathEdgeSet,
		double	DotTolerance,
		int	SourceEID,
		int32	RemoveV,
		const FVector3d &	RemoveVPos,
		int32	KeepV,
		const FVector3d &	KeepVPos,
		const FVector3d &	EdgeDir,
		bool	bPreserveTriangleGroups,
		bool	bPreserveUVsForMesh,
		bool	bPreserveVertexUVs,
		bool	bPreserveOverlayUVs,
		float	UVEqualThresholdSq,
		bool	bPreserveVertexNormals,
		float	NormalEqualCosThreshold
	)

static

Test if a given edge collapse would change the mesh shape, mesh triangle group shape, or UVs unacceptably

Test if a given edge collapse would change the mesh shape or UVs unacceptably

◆ CollapseWouldHurtTriangleQuality()

bool FLocalPlanarSimplify::CollapseWouldHurtTriangleQuality	(	const FDynamicMesh3 &	Mesh,
		const FVector3d &	RemoveVNormal,
		int32	RemoveV,
		const FVector3d &	RemoveVPos,
		int32	KeepV,
		const FVector3d &	KeepVPos,
		double	TryToImproveTriQualityThreshold,
		bool	bHasMultipleNormals = `false`
	)

static

Test if a given edge collapse would cause a triangle flip or other unacceptable decrease in mesh quality Specialized for collapsing at flat triangles

Parameters

Mesh	The mesh to query
RemoveVNormal	Only used if bHasMultipleNormals==false, i.e. if the surface is locally flat, to avoid recomputing the normal. The normal for all triangles surrounding RemoveV.
RemoveV	The vertex to consider removing by an edge collapse
RemoveVPos	The position of the vertex RemoveV
KeepV	The vertex that is not being removed in the edge collapse
KeepVPos	The position of vertex KeepV
TryToImproveTriQualityThreshold	Threshold for triangle quality (see comment for class member, above)
bHasMultipleNormals	If false, assume the triangulation is locally flat, so we can use ExpectNormal instead of recomputing the expected normal

Test if a given edge collapse would cause a triangle flip or other unacceptable decrease in mesh quality

◆ IsDevelopableAlongEdge()

bool FLocalPlanarSimplify::IsDevelopableAlongEdge	(	const FDynamicMesh3 &	Mesh,
		int	EID,
		int	VID,
		double	DotTolerance,
		FVector3d &	NormalA,
		bool &	bIsFlat
	)

static

Test if the triangles connected to a vertex could be flattened by folding along the given edge

Parameters

Mesh	The mesh to query
EID	The edge around which the triangles are allowed to fold
VID	The vertex to query
DotTolerance	If the dot product of two normals are >= this tolerance, the normals are considered equivalent
The	normal of the first triangle attached to the vertex.

Returns: Whether all the triangles were coplanar

◆ IsFlat()

bool FLocalPlanarSimplify::IsFlat	(	const FDynamicMesh3 &	Mesh,
		int	VID,
		double	DotTolerance,
		FVector3d &	OutFirstNormal
	)

static

Test if the triangles connected to a vertex are all coplanar

Parameters

Mesh	The mesh to query
VID	The vertex to query
DotTolerance	If the dot product of two normals are >= this tolerance, the normals are considered equivalent
The	normal of the first triangle attached to the vertex.

Returns: Whether all the triangles were coplanar

◆ SimplifyAlongEdges()

void FLocalPlanarSimplify::SimplifyAlongEdges	(	FDynamicMesh3 &	Mesh,
		TSet< int32 > &	InOutEdges,
		TUniqueFunction< void(const DynamicMeshInfo::FEdgeCollapseInfo &)>	ProcessCollapse = `nullptr`
	)		const

Simplify Mesh along the given edges, and update the edge set accordingly

Parameters

Mesh	Mesh to simplify
InOutEdges	Edges to simplify along – will be updated to remove any edges that have been collapsed by simplification
ProcessCollapse	Optional function to be called whenever the simplification collapses an edge

Member Data Documentation

◆ bPreserveOverlayUVs

bool UE::Geometry::FLocalPlanarSimplify::bPreserveOverlayUVs = true

Prevent simplification from distorting overlay UVs

◆ bPreserveTriangleGroups

bool UE::Geometry::FLocalPlanarSimplify::bPreserveTriangleGroups = true

Prevent simplification from distorting triangle groups

◆ bPreserveVertexNormals

bool UE::Geometry::FLocalPlanarSimplify::bPreserveVertexNormals = true

Prevent simplification from distorting vertex normals

◆ bPreserveVertexUVs

bool UE::Geometry::FLocalPlanarSimplify::bPreserveVertexUVs = true

Prevent simplification from distorting vertex UVs

◆ NormalDistortTolerance

float UE::Geometry::FLocalPlanarSimplify::NormalDistortTolerance = .01f

When preserving normals, sets maximum allowed change in normals from collapsing an edge, measured at the removed vertex in degrees

◆ SimplificationAngleTolerance

double UE::Geometry::FLocalPlanarSimplify::SimplificationAngleTolerance = .1

Degrees of deviation from coplanar that we will still simplify

◆ TryToImproveTriQualityThreshold

double UE::Geometry::FLocalPlanarSimplify::TryToImproveTriQualityThreshold = .25

If triangle quality (aspect ratio) is worse than this threshold, only simplify in ways that improve quality. If <= 0, triangle quality is ignored. Note: For aspect ratio we use definition: 4*TriArea / (sqrt(3)*MaxEdgeLen^2), ref: https://people.eecs.berkeley.edu/~jrs/papers/elemj.pdf p.53 Equilateral triangles have value 1; Smaller values -> lower quality

◆ UVDistortTolerance

float UE::Geometry::FLocalPlanarSimplify::UVDistortTolerance = FMathf::ZeroTolerance

When preserving UVs, sets maximum allowed change in UV coordinates from collapsing an edge, measured at the removed vertex

The documentation for this class was generated from the following files:

Engine/Source/Runtime/GeometryCore/Public/Operations/LocalPlanarSimplify.h
Engine/Source/Runtime/GeometryCore/Private/Operations/LocalPlanarSimplify.cpp

Public Member Functions

Static Public Member Functions

Public Attributes

Member Function Documentation

◆ CollapseDegenerateEdges()

◆ CollapseWouldChangeShapeOrUVs()

◆ CollapseWouldHurtTriangleQuality()

◆ IsDevelopableAlongEdge()

◆ IsFlat()

◆ SimplifyAlongEdges()

Member Data Documentation

◆ bPreserveOverlayUVs

◆ bPreserveTriangleGroups

◆ bPreserveVertexNormals

◆ bPreserveVertexUVs

◆ NormalDistortTolerance

◆ SimplificationAngleTolerance

◆ TryToImproveTriQualityThreshold

◆ UVDistortTolerance