environment::field::aggregation::HashGrid Class Reference

#include <HashGrid.h>

Public Member Functions
	HashGrid ()=default
	An empty grid; every query reports nothing.
	HashGrid (std::span< const Box > boxes, double cellSize)
double	CellSize () const
	The cell edge in use [m].
std::size_t	CellCount () const
	The number of cells.
template<class Visitor >
void	ForEachCandidate (const Box &query, Visitor &&visit) const
void	Candidates (const Box &query, std::vector< std::uint32_t > &out) const
	Appends the ids of the boxes that overlap the query box to out (cleared first).

Static Public Attributes
static constexpr std::size_t	kMaxCells = 4'000'000
	The largest number of cells; a larger domain gets larger cells.

Detailed Description

Index of boxes by horizontal cell, for fast "which boxes touch this query box" lookups.

The grid has square cells. Each box is listed in every cell its horizontal extent touches, together with its own bounds, so a query tests the vertical range and the exact box before it reports a box. A box is reported once per query, however many cells both share.

The grid is immutable after construction, so concurrent queries are safe.

Constructor & Destructor Documentation

HashGrid()

environment::field::aggregation::HashGrid::HashGrid	(	std::span< const Box >	boxes,
		double	cellSize
	)

Builds the grid.

Parameters

[in]	boxes	One box per item; the item id is the index. Bounds must be finite.
[in]	cellSize	Cell edge [m]. A value of zero or less takes the median of the longer horizontal box side. It is enlarged when the cell count would pass kMaxCells.

Member Function Documentation

ForEachCandidate()

template<class Visitor >

void environment::field::aggregation::HashGrid::ForEachCandidate ( const Box &  query, Visitor &&  visit  ) const

inline

Calls visit(id) once for each box that overlaps the query box.

The order is unspecified.

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

• webfhsim/reloadrepos/fhsim_environment/src/environment/aggregation/HashGrid.h