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FConvexDecomposition3

API > API/Runtime > API/Runtime/GeometryCore

   
Name FConvexDecomposition3
Type class
Header File /Engine/Source/Runtime/GeometryCore/Public/CompGeom/ConvexDecomposition3.h
Include Path #include "CompGeom/ConvexDecomposition3.h"

Syntax

class FConvexDecomposition3

Constructors

Name Remarks Include Path Unreal Specifiers

FConvexDecomposition3 ( const FDynamicMesh3& SourceMesh,
const FPreprocessMeshOptions& Options
)

   CompGeom/ConvexDecomposition3.h  

FConvexDecomposition3 ( const FDynamicMesh3& SourceMesh,
bool bMergeEdges
)

   CompGeom/ConvexDecomposition3.h  
  CompGeom/ConvexDecomposition3.h  

Structs

Name Remarks
FConvexPart Representation of a convex hull in the decomposition + associated information to help further split or merge.
FMergeSettings  
FPreprocessMeshOptions  
FProximity Edge in a graph of merge candidates, indicating which Decomposition parts could be merged together Note a proximity link does not guarantee that the geometry (or convex hulls) are touching

Variables

Public

Name Type Remarks Include Path Unreal Specifiers
BiasToRemoveTooThinParts double A bias term to favor merging away 'too thin' parts before merging other parts, expressed as a volume in units s.t. CompGeom/ConvexDecomposition3.h  
bSplitDisconnectedComponents bool Whether to, after each split, also detect whether a part is made up of disconnected pieces and further split them if so. CompGeom/ConvexDecomposition3.h  
bTreatAsSolid bool Whether to treat the input mesh as a solid shape controls whether, e.g., a hole-fill is performed after splitting the mesh to close off the resulting parts. CompGeom/ConvexDecomposition3.h  
ConnectedComponentTolerance double Threshold for considering two components to be touching. CompGeom/ConvexDecomposition3.h  
ConvexEdgeAngleMoreSamplesThreshold double Angle at edge above which we take 5 sample planes instead of 3, to better cover the wider range (expressed in degrees) CompGeom/ConvexDecomposition3.h  
ConvexEdgeAngleThreshold double Angle at edge above which we don't sample it as a convex edge (expressed in degrees) CompGeom/ConvexDecomposition3.h  
CutLargestAxisErrorScale double Scale factor for error on the largest axis; slightly favoring cutting on the largest axis helps get more consistent result when no initial cut will reduce error (e.g. a torus) CompGeom/ConvexDecomposition3.h  
Decomposition TIndirectArray< FConvexPart > All convex hulls parts in the convex decomposition Note this must be an indirect array, not a TArray, because FConvexPart holds an FDynamicMesh3 mesh, which is not trivially movable CompGeom/ConvexDecomposition3.h  
DecompositionToProximity TMultiMap< int32, int32 > Mapping from Decomposition indices to Proximity indices. CompGeom/ConvexDecomposition3.h  
MaxConvexEdgePlanes int32 Maximum number of convex edges to sample for possible cutting planes when calling SplitWorst() to generate an initial convex decomposition Larger values will cost more to run but can let the algorithm find a cleaner decomposition CompGeom/ConvexDecomposition3.h  
OnPlaneTolerance double Maximum 'on plane' distance for points during planar cuts. CompGeom/ConvexDecomposition3.h  
Proximities TArray< FProximity > All potential merge edges between Decomposition FConvexParts. CompGeom/ConvexDecomposition3.h  
ProximityTolerance double Threshold for considering two convex parts close enough to consider merging. CompGeom/ConvexDecomposition3.h  
RestrictMergeSearchToLocalAfterTestNumConnections int32 If > 0, search for best merges will be restricted to a greedy local search after testing this many connections. Helpful when there are many potential merges. CompGeom/ConvexDecomposition3.h  
ResultTransform FTransformSRT3d Transform taking the result hull vertices back to the original space of the inputs; automatically applied by GetVertices() CompGeom/ConvexDecomposition3.h  
ThickenAfterHullFailure double If greater than zero, we can 'inflate' the input shape by this amount along any degenerate axes in cases where the hull failed to construct due to the input being coplanar/colinear. CompGeom/ConvexDecomposition3.h  

Protected

Name Type Remarks Include Path Unreal Specifiers
NegativeSpace FSphereCovering Negative space to attempt to protect; can be referenced by the Decomposition parts. CompGeom/ConvexDecomposition3.h  

Functions

Public

Name Remarks Include Path Unreal Specifiers

void Compact()

 Compact the decomposition representation to the minimal needed for output: Just the hull vertices and triangles, no internal geometry This will prevent some further processing on the representation; to ensure it is called only when the geometry is no longer needed, instead of calling this directly, call MergeBest with bAllowCompact=true CompGeom/ConvexDecomposition3.h  

void Compute ( int32 NumOutputHulls,
int32 NumAdditionalSplits,
double ErrorTolerance,
double MinThicknessTolerance,
int32 MaxOutputHulls,
bool bOnlySplitIfNegativeSpaceCovered
)

 Compute a decomposition with the desired number of hulls Note: A future version of this function may replace NumOutputHulls with MaxOutputHulls, but this version keeps both parameters for compatibility / consistent behavior. CompGeom/ConvexDecomposition3.h  

double ConvertDistanceToleranceToLocalSpace ( double DistTolerance
) const

 Simple helper to convert an error tolerance expressed in world space to local space CompGeom/ConvexDecomposition3.h  

double ConvertDistanceToleranceToLocalVolumeTolerance ( double DistTolerance
) const

 Simple helper to convert an error tolerance expressed in world space to a local-space volume tolerance CompGeom/ConvexDecomposition3.h  

const int32 CountMergedParts()

   CompGeom/ConvexDecomposition3.h  

void DeleteProximity ( TArray< int32 >&& ToRemove,
bool bDeleteMapReferences
)

 Helper function to delete a proximity relationship, and fix index references to account for the new array ordering CompGeom/ConvexDecomposition3.h  

void FixHullOverlapsInNegativeSpace ( double NegativeSpaceTolerance,
double NegativeSpaceMinRadius
)

 Fix overlaps between current Decomposition and associated NegativeSpace, using the saved associations in the FConvexPart::OverlapsNegativeSpace Note the tolerance and min radius may not be the same as originally used to generate the negative space; they should just be large enough to avoid 'locking' the merge step for any hulls that still overlap negative space after splitting CompGeom/ConvexDecomposition3.h  

FDynamicMesh3 GetHullMesh ( int32 HullIdx
) const

   CompGeom/ConvexDecomposition3.h  

const int32 GetHullSourceID ( int32 HullIdx
) const

   CompGeom/ConvexDecomposition3.h  

const FDynamicMesh3 & GetInternalMesh ( int32 HullIdx
) const

 Get the non-hull geometry underlying a part of the convex decomposition. CompGeom/ConvexDecomposition3.h  
Get the current negative space tracked by the convex decomposition Note: Does not include externally-managed negative space passed to MergeBest. CompGeom/ConvexDecomposition3.h  

TArray< FIndex3i > const & GetTriangles ( int32 HullIdx
) const

   CompGeom/ConvexDecomposition3.h  

TArray< TVector< RealType > > GetVertices ( int32 HullIdx,
bool bTransformedToOutput
) const

   CompGeom/ConvexDecomposition3.h  

void InitializeFromHulls ( int32 NumHulls,
TFunctionRef< double(int32)> HullVolumes,
TFunctionRef< int32(int32)> HullNumVertices,
TFunctionRef< FVector3d(int32, int32)> HullVertices,
TArrayView< const TPair< int32, int32 > > Proximity
)

 Initialize from convex hulls allows the caller to only use the hull merging phase of the algorithm CompGeom/ConvexDecomposition3.h  

void InitializeFromIndexMesh ( TArrayView< const FVector3f > Vertices,
TArrayView< const FIntVector > Faces,
const FPreprocessMeshOptions& Options,
int32 FaceVertexOffset
)

 Initialize convex decomposition with a triangle index mesh CompGeom/ConvexDecomposition3.h  

void InitializeFromIndexMesh ( TArrayView< const FVector3f > Vertices,
TArrayView< const FIntVector > Faces,
bool bMergeEdges,
int32 FaceVertexOffset
)

 Initialize convex decomposition with a triangle index mesh CompGeom/ConvexDecomposition3.h  

void InitializeFromMesh ( const FDynamicMesh3& SourceMesh,
const FPreprocessMeshOptions& Options
)

   CompGeom/ConvexDecomposition3.h  

void InitializeFromMesh ( const FDynamicMesh3& SourceMesh,
bool bMergeEdges
)

   CompGeom/ConvexDecomposition3.h  

bool InitializeNegativeSpace ( const FNegativeSpaceSampleSettings& Settings,
TArrayView< const FVector3d > RequestedSamples
)

 Find negative space that should be protected. CompGeom/ConvexDecomposition3.h  

void InitializeProximityFromDecompositionBoundingBoxOverlaps ( double BoundsExpandByMinDimFactor,
double BoundsExpandByMaxDimFactor,
double MinBoundsExpand
)

 Create the proximity graph from the current decomposition, using bounding box overlaps. CompGeom/ConvexDecomposition3.h  

bool IsInputSolid ()

 Test whether the input mesh (after preprocessing) is solid. CompGeom/ConvexDecomposition3.h  

int32 MergeBest ( const FMergeSettings& Settings
)

 Merge the pairs of convex hulls in the decomposition that will least increase the error. CompGeom/ConvexDecomposition3.h  

int32 MergeBest ( int32 TargetNumParts,
double ErrorTolerance,
double MinThicknessTolerance,
bool bAllowCompact,
bool bRequireHullTriangles,
int32 MaxOutputHulls,
const FSphereCovering* OptionalNegativeSpace,
const FTransform* OptionalTransformIntoNegativeSpace
)

 Merge the pairs of convex hulls in the decomposition that will least increase the error. CompGeom/ConvexDecomposition3.h  

int32 NumHulls()

 Results CompGeom/ConvexDecomposition3.h  

int32 SplitWorst ( bool bCanSkipUnreliableGeoVolumes,
double ErrorTolerance,
bool bOnlySplitIfNegativeSpaceCovered,
double MinSplitSizeInWorldSpace
)

 Split the worst convex part, and return the increase in the total number of convex parts after splitting (can be more than 1 if result has multiple separate connected components) Note: could return 0 if no splits were possible CompGeom/ConvexDecomposition3.h  

void UpdateProximitiesAfterSplit ( int32 SplitIdx,
int32 NewIdxStart,
FPlane3d CutPlane,
int32 SecondSideIdxStart,
double OrigHullVolume
)

 Helper function to update all proximity data after splitting an FConvexPart apart CompGeom/ConvexDecomposition3.h  

Static

Name Remarks Include Path Unreal Specifiers

static bool ConvexPartVsSphereOverlap ( const FConvexPart& Part,
FVector3d Center,
double Radius,
const FTransform* TransformIntoSphereSpace,
double* OutDistanceSq
)

 Tests if a convex part overlaps a sphere CompGeom/ConvexDecomposition3.h  

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