nuri::VoxelGrid Class Reference

A uniform voxel-grid (cell list) index for 3D point clouds with a fixed neighbor cutoff. More...

#include <nuri/core/geometry.h>

Public Types
using	Points = ConstRef<Matrix3Xd>

Public Member Functions
	VoxelGrid ()=default
	VoxelGrid (Points pts, double cutoff)
void	rebuild (Points pts, double cutoff=-1.0)
void	find_neighbors_d (const Vector3d &pt, std::vector< int > &idxs, std::vector< double > &distsq) const
	Find indices of all points within the build-time cutoff of a query point.
void	find_neighbors_grid (const VoxelGrid &grid, std::vector< int > &self, std::vector< int > &other) const
	Find all pairs (i, j) where i is in *this and j is in grid and the distance between the points is within the build-time cutoff of *this.
std::vector< std::vector< int > >	find_neighbors_grid (const VoxelGrid &grid) const
	Convenience overload returning a per-self adjacency list.
void	find_neighbors_self (std::vector< int > &left, std::vector< int > &right) const
	Find all non-redundant pairs of neighbors within the build-time cutoff.
const Matrix3Xd &	pts () const
	The grid-owned, cell-reordered copy of the input coordinates.
double	cutoff () const
const Vector3d &	origin () const
const Array3i &	dims () const
int	num_cells () const
const ArrayXi &	cell_offset () const
const ArrayXi &	cell_pts () const

Detailed Description

A uniform voxel-grid (cell list) index for 3D point clouds with a fixed neighbor cutoff.

Unlike OCTree, the cutoff distance is baked in at build time and equals the voxel edge length. Neighbor queries therefore only need to scan the 3x3x3 = 27 voxels around each query point. The grid stores its contents in a CSR-style layout:

• cell_offset() is a prefix-sum array of length num_cells() + 1.
• cell_pts() contains all atom indices grouped by voxel, of length equal to the number of input points.

The grid owns its own copy of the input coordinates, reordered so that points belonging to the same voxel are contiguous in memory. pts() returns this reordered copy, not the original input; the p-th column of pts() corresponds to the original input point cell_pts()[p]. The original point set is not referenced after rebuild() returns, so the caller is free to mutate or destroy it.

Member Typedef Documentation

Points

using nuri::VoxelGrid::Points = ConstRef<Matrix3Xd>

Constructor & Destructor Documentation

VoxelGrid() [1/2]

nuri::VoxelGrid::VoxelGrid ( )

default

VoxelGrid() [2/2]

nuri::VoxelGrid::VoxelGrid ( Points pts, double cutoff )

inlineexplicit

Member Function Documentation

cell_offset()

const ArrayXi & nuri::VoxelGrid::cell_offset ( ) const

inline

cell_pts()

const ArrayXi & nuri::VoxelGrid::cell_pts ( ) const

inline

cutoff()

double nuri::VoxelGrid::cutoff ( ) const

inline

dims()

const Array3i & nuri::VoxelGrid::dims ( ) const

inline

find_neighbors_d()

void nuri::VoxelGrid::find_neighbors_d	(	const Vector3d &	pt,
		std::vector< int > &	idxs,
		std::vector< double > &	distsq ) const

Find indices of all points within the build-time cutoff of a query point.

Parameters

pt	The query point.
idxs	Output indices into pts() of the matched points.
distsq	Output squared distances corresponding to each matched index.

find_neighbors_grid() [1/2]

std::vector< std::vector< int > > nuri::VoxelGrid::find_neighbors_grid

(

const VoxelGrid &

grid

)

const

Convenience overload returning a per-self adjacency list.

Parameters

grid	The other voxel grid; only its point set is used.

Returns

A vector of size pts().cols(); the i-th entry contains the indices into grid whose points are within the cutoff of point i in *this.

find_neighbors_grid() [2/2]

void nuri::VoxelGrid::find_neighbors_grid	(	const VoxelGrid &	grid,
		std::vector< int > &	self,
		std::vector< int > &	other ) const

Find all pairs (i, j) where i is in *this and j is in grid and the distance between the points is within the build-time cutoff of *this.

Parameters

grid	The other voxel grid; only its point set is used.
self	Output indices into *this.
other	Output indices into grid.

find_neighbors_self()

void nuri::VoxelGrid::find_neighbors_self	(	std::vector< int > &	left,
		std::vector< int > &	right ) const

Find all non-redundant pairs of neighbors within the build-time cutoff.

Parameters

left	Output indices of the first member of each pair.
right	Output indices of the second member of each pair.

Each pair is reported exactly once with i != j; if (i, j) is emitted then (j, i) will not be. The ordering between left[k] and right[k] is unspecified.

num_cells()

int nuri::VoxelGrid::num_cells ( ) const

inline

origin()

const Vector3d & nuri::VoxelGrid::origin ( ) const

inline

pts()

const Matrix3Xd & nuri::VoxelGrid::pts ( ) const

inline

The grid-owned, cell-reordered copy of the input coordinates.

The p-th column corresponds to the original input point at index cell_pts()[p]. Use cell_pts() to translate between the internal layout and the caller's indexing.

rebuild()

void nuri::VoxelGrid::rebuild ( Points pts, double cutoff = -1.0 )

inline

---

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

• include/nuri/core/geometry.h