Class QAccelPlot::PointSpatialIndex¶

ClassList > QAccelPlot > PointSpatialIndex

Uniform-grid spatial index for nearest-point queries over large point sets. More...

#include <PointSpatialIndex.hpp>

Classes¶

Type	Name
struct	Mapping Coordinate mapping applied before indexing.

Public Functions¶

Type	Name
void	build (const float * data, int pointCount, int stride, Mapping mapping) Rebuilds the index from pointCount points in__data using__stride floats per point.
void	build (const float * data, int pointCount, int stride=2) Rebuilds the index with the identity mapping, for linear axes.
void	clear () Removes all indexed points.
int	columnCount () const Returns the number of grid columns of the last build; 0 when no point is indexed.
bool	isEmpty () const Returns `true` when no valid point is indexed.
Mapping	mapping () const Returns the mapping used by the last build.
int	nearest (double x, double y, double radiusX, double radiusY) const Returns the index of the point nearest to ( x _,_y ) inside the ellipse with radii__radiusX and__radiusY , or -1 when none. All arguments are in mapped space.
int	rowCount () const Returns the number of grid rows of the last build; 0 when no point is indexed.
int	validPointCount () const Returns the number of indexed (valid) points.

Public Static Functions¶

Type	Name
bool	mapCoordinate (double value, bool logarithmic, double & mapped) Maps value for indexing. Returns`false` when the value cannot be indexed.
int	nearestByScan (const float * data, int pointCount, int stride, Mapping mapping, double x, double y, double radiusX, double radiusY) Returns what `nearest()` returns on an index built from the same points, without building one.

Detailed Description¶

Points are read from a flat float array with a configurable stride whose first two components are x and y. Coordinates are indexed in mapped space: log10 of the value on logarithmic axes, the value itself otherwise, so a pixel radius converts to a constant mapped-space radius at any zoom level. Non-finite points, and non-positive points on logarithmic axes, are excluded.

Cells are stored in a compressed layout (cellStart_ offsets into one index array), which keeps a rebuild over a million points to a handful of allocations.

See also: PointCloud

Public Functions Documentation¶

function build¶

Rebuilds the index from pointCount points in__data using__stride floats per point.

void QAccelPlot::PointSpatialIndex::build (
    const float * data,
    int pointCount,
    int stride,
    Mapping mapping
)

function build¶

Rebuilds the index with the identity mapping, for linear axes.

void QAccelPlot::PointSpatialIndex::build (
    const float * data,
    int pointCount,
    int stride=2
)

A separate overload rather than a defaulted Mapping argument: a nested class's default member initializers are not usable in a default argument until the enclosing class is complete, which MSVC accepts but Clang and GCC reject.

function clear¶

Removes all indexed points.

void QAccelPlot::PointSpatialIndex::clear ()

function columnCount¶

Returns the number of grid columns of the last build; 0 when no point is indexed.

int QAccelPlot::PointSpatialIndex::columnCount () const

function isEmpty¶

Returns true when no valid point is indexed.

bool QAccelPlot::PointSpatialIndex::isEmpty () const

function mapping¶

Returns the mapping used by the last build.

Mapping QAccelPlot::PointSpatialIndex::mapping () const

function nearest¶

Returns the index of the point nearest to ( x _,_y ) inside the ellipse with radii__radiusX and__radiusY , or -1 when none. All arguments are in mapped space.

int QAccelPlot::PointSpatialIndex::nearest (
    double x,
    double y,
    double radiusX,
    double radiusY
) const

Distance is normalized by the radii, so an anisotropic pixel radius behaves like a circle on screen. Ties resolve to the highest index, the point drawn last.

function rowCount¶

Returns the number of grid rows of the last build; 0 when no point is indexed.

int QAccelPlot::PointSpatialIndex::rowCount () const

function validPointCount¶

Returns the number of indexed (valid) points.

int QAccelPlot::PointSpatialIndex::validPointCount () const

Public Static Functions Documentation¶

function mapCoordinate¶

Maps value for indexing. Returnsfalse when the value cannot be indexed.

static bool QAccelPlot::PointSpatialIndex::mapCoordinate (
    double value,
    bool logarithmic,
    double & mapped
)

function nearestByScan¶

Returns what nearest() returns on an index built from the same points, without building one.

static int QAccelPlot::PointSpatialIndex::nearestByScan (
    const float * data,
    int pointCount,
    int stride,
    Mapping mapping,
    double x,
    double y,
    double radiusX,
    double radiusY
)

Tests every point, so a call costs one pass over data. That is cheaper than a rebuild while the data is replaced after only a few queries.

The documentation for this class was generated from the following file QAccelPlot/src/QAccelPlot/series/PointSpatialIndex.hpp