FSegmentTree3 | Unreal Engine 5.6 Documentation

API > API/Runtime > API/Runtime/GeometryCore

FSegmentTree3 is a spatial data structure for a set of 3D line segments. The line segments are provided externally, and each segment can have an arbitrary ID. The line segment geometry (ie endpoints) are stored directly by FSegmentTree3, so the class does not hold onto any reference to the source geometry (ie unlike FMeshAABBTree3).

Available queries:

FindNearestSegment(Point) - finds the nearest segment to the 3D point
FindNearestVisibleSegmentHitByRay(Ray) - finds the nearest segment that is "hit" by the ray under a tolerance check (see comments below). This is mainly intended for UI hit testing.


Name	FSegmentTree3
Type	class
Header File	/Engine/Source/Runtime/GeometryCore/Public/Spatial/SegmentTree3.h
Include Path	#include "Spatial/SegmentTree3.h"

Syntax

class FSegmentTree3

Structs

Name	Remarks
FBoxesSet	This is a temporary data structure used in tree building
FRayNearestSegmentInfo	Information on a nearest-segment returned by query functions
FSegment	FSegment is a 3D line segment with an external identifier
FTreeBox	Storage for Box Nodes.

Typedefs

Name	Type	Remarks	Include Path
GetSplitAxisFunc	TUniqueFunction< int(int Depth, const FAxisAlignedBox3d &Box)>		Spatial/SegmentTree3.h

Functions

Public

Name	Remarks	Include Path
void Build ( SegmentIDEnumerable Enumerable, GetSegmentFunc GetSegmentForID, int32 NumSegmentsHint )	Build the segment tree based on the given Enumerable (ie something that supports a range-based for loop over a set of integer IDs) and a function GetSegmentForID that returns the 3D line segment for a given ID.	Spatial/SegmentTree3.h
bool FindNearestSegment ( const FVector3d& P, FSegment& NearestSegmentOut, const IMeshSpatial::FQueryOptions& Options ) const	Find the nearest segment to query point P, and return it in NearestSegmentOut	Spatial/SegmentTree3.h
bool FindNearestVisibleSegmentHitByRay ( const FRay3d& Ray, TFunctionRef< bool(int32, const FVector3d&, const FVector3d&)> WithinToleranceCheck, FSegment& NearestHitSegmentOut, FRayNearestSegmentInfo& NearestInfo, const IMeshSpatial::FQueryOptions& Options ) const	Find the segment that is hit by a 3D ray under a function WithinToleranceCheck, which will be called with the Ray and Segment points.	Spatial/SegmentTree3.h
void SetTolerance ( double Tolerance )	Sets the box intersection tolerance TODO: move into the IMeshSpatial::FQueryOptions and delete this function	Spatial/SegmentTree3.h

Protected

Name	Remarks	Include Path
void BuildTopDown ( TArray< int >& SegmentIndices, TArray< FVector3d >& SegmentCenters, int32 NumSegments )		Spatial/SegmentTree3.h
void FindNearestSegmentInternal ( int BoxIndex, const FVector3d& P, double& NearestDistSqr, int& NearSegmentIdx, const IMeshSpatial::FQueryOptions& Options ) const		Spatial/SegmentTree3.h
void FindNearestVisibleSegmentHitByRayInternal ( int BoxIndex, const FRay3d& Ray, TFunctionRef< bool(int32, const FVector3d&, const FVector3d&)> WithinToleranceCheck, int& NearSegmentIdx, FRayNearestSegmentInfo& NearestInfo, const IMeshSpatial::FQueryOptions& Options ) const	This function tries to find the segment "hit" by the ray, where the definition of "hit" tries to balance distance from the ray origin (ie "close to eye") and distance from the hit segment (ie "on the line").	Spatial/SegmentTree3.h
double GetBoxDistanceSqr ( int BoxIndex, const FVector3d& V ) const		Spatial/SegmentTree3.h
double GetRayBoxIntersectionParam ( int BoxIndex, const FRay3d& Ray, double Radius ) const		Spatial/SegmentTree3.h
int SplitSegmentSetMidpoints ( TArray< int >& SegmentIndices, TArray< FVector3d >& SegmentCenters, int StartIdx, int Count, int Depth, int MinSegmentCount, FBoxesSet& SegmentBoxes, FBoxesSet& Nodes, FAxisAlignedBox3d& Box )		Spatial/SegmentTree3.h

Static

Name	Remarks	Include Path	Unreal Specifiers
static GetSplitAxisFunc MakeDefaultSplitAxisFunc()		Spatial/SegmentTree3.h

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