UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType > Class Template Reference

#include <SparseNarrowBandMeshSDF.h>

Classes
struct	FScatterCounter
struct	FTriBBox
struct	FTriIDBlockGrid

Public Types
enum	EComputeModes { NarrowBandOnly = 1 , NarrowBand_SpatialFloodFill = 2 }
enum	EInsideModes { CrossingCount = 0 , WindingCount = 1 }

Public Member Functions
	TSparseNarrowBandMeshSDF (const TriangleMeshType *Mesh=nullptr, float CellSize=1.f, TMeshAABBTree3< TriangleMeshType > *Spatial=nullptr)
TTriLinearGridInterpolant< TSparseNarrowBandMeshSDF >	MakeInterpolant ()
bool	Validate (const FAxisAlignedBox3d &Bounds)
bool	Compute (FAxisAlignedBox3d Bounds)
FVector3i	Dimensions () const
const FBlockedGrid3i &	GetClosestTriGrid () const
const FBlockedGrid3i &	GetIntersectionsGrid () const
float	At (int32 I, int32 J, int32 K) const
float	operator[] (const FVector3i &ijk) const
float	GetValue (const FVector3i &ijk) const
FVector3f	CellCenter (int32 I, int32 J, int32 K) const

Static Public Member Functions
static bool	ShouldUseSpatial (int32 ExactCells, double CellSize, double AvgEdgeLen)

Public Attributes
const TriangleMeshType *	Mesh = nullptr
TMeshAABBTree3< TriangleMeshType > *	Spatial = nullptr
TUniqueFunction< bool(const FVector3d &)>	IsInsideFunction
float	CellSize
int	ExactBandWidth = 1
FVector3d	ExpandBounds = FVector3d::Zero()
bool	bUseParallel = true
int	ApproxMaxCellsPerDimension = 4096
EComputeModes	ComputeMode = EComputeModes::NarrowBandOnly
double	NarrowBandMaxDistance = 0
bool	bComputeSigns = true
EInsideModes	InsideMode = EInsideModes::WindingCount
bool	bWantClosestTriGrid = false
bool	bWantIntersectionsGrid = true
TFunction< bool()>	CancelF
FVector3f	GridOrigin
FBlockedGrid3f	Grid

Protected Attributes
FBlockedGrid3i	ClosestTriGrid
FBlockedGrid3i	IntersectionsGrid

Detailed Description

template<class TriangleMeshType>
class UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >

Compute discretely-sampled (ie gridded) signed distance field for a mesh within a specified narrow band.

The basic approach is, first compute exact Distances in a narrow band, and then The resulting unsigned Grid is then signed using ray-intersection counting, which is also computed on the Grid, so no BVH is necessary

The underlying grid data structures are blocked grids where spatial blocks are allocated as needed, so the memory footprint will generally be much lower than the TSweepingMeshSDF, or TCachingMeshSDF. But if distances in the full grid domain are desired (not just a narrow band), then the TSweepingMeshSDF should be used.

You can optionally provide a spatial data structure to allow faster computation of narrow-band Distances; this is most beneficial if we want a wider band

Caveats:

• the "narrow band" is based on triangle bounding boxes, so it is not necessarily that "narrow" if you have large triangles on a diagonal to Grid axes

This code is based on the implementation found at https://github.com/christopherbatty/SDFGen

Member Enumeration Documentation

EComputeModes

template<class TriangleMeshType >

enum UE::Geometry::TSparseNarrowBandMeshSDF::EComputeModes

Enumerator
NarrowBandOnly
NarrowBand_SpatialFloodFill

EInsideModes

template<class TriangleMeshType >

enum UE::Geometry::TSparseNarrowBandMeshSDF::EInsideModes

Enumerator
CrossingCount
WindingCount

Constructor & Destructor Documentation

TSparseNarrowBandMeshSDF()

template<class TriangleMeshType >

UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::TSparseNarrowBandMeshSDF ( const TriangleMeshType *  Mesh = nullptr, float  CellSize = 1.f, TMeshAABBTree3< TriangleMeshType > *  Spatial = nullptr  )

inline

Parameters

Mesh	Triangle mesh to build an SDF around
CellSize	Spacing between Grid points
Spatial	Optional AABB tree; note it must be provided if ComputeMode is set to NarrowBand_SpatialFloodFill

Member Function Documentation

At()

template<class TriangleMeshType >

float UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::At ( int32  I, int32  J, int32  K  ) const

inline

Returns

the distance value at the specified grid cell.

CellCenter()

template<class TriangleMeshType >

FVector3f UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::CellCenter ( int32  I, int32  J, int32  K  ) const

inline

Returns

the physical space location of specified grid point.

Compute()

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Compute ( FAxisAlignedBox3d  Bounds )

inline

Compute the SDF

Parameters

Bounds

Bounding box for the mesh data (passed as param it is usually already available, depending on TriangleMeshType and whether an AABB tree was provided)

Returns

false if cancelled or failed (e.g. due to invalid arguments); true otherwise

Dimensions()

template<class TriangleMeshType >

FVector3i UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Dimensions ( ) const

inline

Returns

the number of cells in each direction

GetClosestTriGrid()

template<class TriangleMeshType >

const FBlockedGrid3i & UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::GetClosestTriGrid ( ) const

inline

Returns

a grid that can be sampled within the narrow band to find the ID of the closest triangle. Note: this is populated during Compute()

GetIntersectionsGrid()

template<class TriangleMeshType >

const FBlockedGrid3i & UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::GetIntersectionsGrid ( ) const

inline

Returns

a grid that can be sampled within the narrow band to find cells that actually contain mesh triangles. Note: this is populated during Compute()

GetValue()

template<class TriangleMeshType >

float UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::GetValue ( const FVector3i &  ijk ) const

inline

Returns

the distance value at the specified grid cell.

MakeInterpolant()

template<class TriangleMeshType >

TTriLinearGridInterpolant< TSparseNarrowBandMeshSDF > UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::MakeInterpolant ( )

inline

operator[]()

template<class TriangleMeshType >

float UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::operator[] ( const FVector3i &  ijk ) const

inline

Returns

the distance value at the specified grid cell.

ShouldUseSpatial()

template<class TriangleMeshType >

static bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ShouldUseSpatial ( int32  ExactCells, double  CellSize, double  AvgEdgeLen  )

inlinestatic

Encodes heuristic for deciding whether it will be faster to use

• NarrowBand_SpatialFloodFill
• Or NarrowBandOnly The heuristic is to use the Spatial method unless you have relatively long edges relative to the width of the narrow band. For a 1-cell wide band, or one where few triangles interact w/ each cell in the band the spatial overhead will probably not be worthwhile. TODO: test and tune this ...

Validate()

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Validate ( const FAxisAlignedBox3d &  Bounds )

inline

Member Data Documentation

ApproxMaxCellsPerDimension

template<class TriangleMeshType >

int UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ApproxMaxCellsPerDimension = 4096

bComputeSigns

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::bComputeSigns = true

bUseParallel

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::bUseParallel = true

bWantClosestTriGrid

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::bWantClosestTriGrid = false

bWantIntersectionsGrid

template<class TriangleMeshType >

bool UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::bWantIntersectionsGrid = true

CancelF

template<class TriangleMeshType >

TFunction<bool()> UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::CancelF

Initial value:

= []()
    {
        return false;
    }

if this function returns true, the calculation will abort

CellSize

template<class TriangleMeshType >

float UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::CellSize

ClosestTriGrid

template<class TriangleMeshType >

FBlockedGrid3i UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ClosestTriGrid

protected

ComputeMode

template<class TriangleMeshType >

EComputeModes UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ComputeMode = EComputeModes::NarrowBandOnly

ExactBandWidth

template<class TriangleMeshType >

int UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ExactBandWidth = 1

ExpandBounds

template<class TriangleMeshType >

FVector3d UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::ExpandBounds = FVector3d::Zero()

Grid

template<class TriangleMeshType >

FBlockedGrid3f UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Grid

GridOrigin

template<class TriangleMeshType >

FVector3f UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::GridOrigin

InsideMode

template<class TriangleMeshType >

EInsideModes UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::InsideMode = EInsideModes::WindingCount

IntersectionsGrid

template<class TriangleMeshType >

FBlockedGrid3i UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::IntersectionsGrid

protected

IsInsideFunction

template<class TriangleMeshType >

TUniqueFunction<bool(const FVector3d&)> UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::IsInsideFunction

Mesh

template<class TriangleMeshType >

const TriangleMeshType* UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Mesh = nullptr

NarrowBandMaxDistance

template<class TriangleMeshType >

double UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::NarrowBandMaxDistance = 0

Spatial

template<class TriangleMeshType >

TMeshAABBTree3<TriangleMeshType>* UE::Geometry::TSparseNarrowBandMeshSDF< TriangleMeshType >::Spatial = nullptr

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

• Engine/Source/Runtime/GeometryCore/Public/Implicit/SparseNarrowBandMeshSDF.h