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  3. FSegmentTree3

FSegmentTree3

[FSegmentTree3](API\Runtime\GeometryCore\Spatial\FSegmentTree3) is a spatial data structure for a set of 3D line segments.

API > API/Runtime > API/Runtime/GeometryCore > API/Runtime/GeometryCore/Spatial

References

   
Module GeometryCore
Header /Engine/Source/Runtime/GeometryCore/Public/Spatial/SegmentTree3.h
Include #include "Spatial/SegmentTree3.h"

Syntax

class FSegmentTree3

Remarks

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.

Variables

  Type Name Description
Protected variable double BoxEps TODO: move BoxEps to IMeshSpatial::FQueryOptions.
Protected variable GetSplitAxisFunc GetSplitAxis  
Protected variable TArray< int > IndexList List of indices for a given Box.
Protected variable int RootBoxIndex RootBoxIndex is the index of the root box of the tree, index into TreeBoxes.
Protected variable TArray< FSegment > SegmentList List of segments
Protected variable int SegmentsEnd IndexList[i] for i < SegmentsEnd is a segment-index list, ie a leaf-box list.
Protected variable int TopDownLeafMaxSegmentCount  
Protected variable TArray< FTreeBox > TreeBoxes  

Functions

  Type Name Description
Public function 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.
Protected function void

BuildTopDown ( TArray< int >& SegmentIndices,
TArray< FVector3d >& SegmentCenters,
int32 NumSegments
)

  
Public function Const bool

FindNearestSegment ( const FVector3d& P,
FSegment& NearestSegmentOut,
const IMeshSpatial::FQueryOptions& Options
)

 Find the nearest segment to query point P, and return it in NearestSegmentOut
Protected function Const void

FindNearestSegmentInternal ( int BoxIndex,
const FVector3d& P,
double& NearestDistSqr,
int& NearSegmentIdx,
const IMeshSpatial::FQueryOptions& Options
)

  
Public function Const bool

FindNearestVisibleSegmentHitByRay ( const FRay3d& Ray,
TFunctionRef< bool(int32, const FVector3d&, const FVector3d&)> WithinToleranceCheck,
FSegment& NearestHitSegmentOut,
FRayNearestSegmentInfo& NearestInfo,
const IMeshSpatial::FQueryOptions& Options
)

 Find the segment that is hit by a 3D ray under a function WithinToleranceCheck, which will be called with the Ray and Segment points.
Protected function Const void

FindNearestVisibleSegmentHitByRayInternal ( int BoxIndex,
const FRay3d& Ray,
TFunctionRef< bool(int32, const FVector3d&, const FVector3d&)> WithinToleranceCheck,
int& NearSegmentIdx,
FRayNearestSegmentInfo& NearestInfo,
const IMeshSpatial::FQueryOptions& Options
)

 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").
Protected function Const double

GetBoxDistanceSqr ( int BoxIndex,
const FVector3d& V
)

  
Protected function Const double

GetRayBoxIntersectionParam ( int BoxIndex,
const FRay3d& Ray,
double Radius
)

  
Protected function Static GetSplitAxisFunc  
Public function void

SetTolerance ( double Tolerance
)

 Sets the box intersection tolerance TODO: move into the IMeshSpatial::FQueryOptions and delete this function
Protected function int

SplitSegmentSetMidpoints ( TArray< int >& SegmentIndices,
TArray< FVector3d >& SegmentCenters,
int StartIdx,
int Count,
int Depth,
int MinSegmentCount,
FBoxesSet& SegmentBoxes,
FBoxesSet& Nodes,
FAxisAlignedBox3d& Box
)

  

Classes

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

Typedefs

Name Description
GetSplitAxisFunc  

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