mesh::DTMThinner Class Reference

Terrain-adaptive Steiner point selector from a DTM raster. More...

#include <dtmthinner.h>

Collaboration diagram for mesh::DTMThinner:

Public Member Functions
	DTMThinner ()
	~DTMThinner ()
	DTMThinner (const DTMThinner &)=delete
DTMThinner &	operator= (const DTMThinner &)=delete
bool	open (const QString &filePath, int band=1)
void	close ()
bool	isOpen () const noexcept
QVector< QPointF >	generatePoints (const MapExtent &domain, const DTMThinnerOptions &opts={}, QVector< double > *outZ=nullptr, const DTMProgressFn &progress={}, const DTMThinnerLimits &limits={}) const
	Generate terrain-significant sample points within domain.
double	pixelSize () const
QString	crsWkt () const
QString	errorMsg () const
double	sampleAt (double x, double y) const
	Sample the DTM at a single map-CRS coordinate. Returns NaN when out-of-bounds or NoData.
void	sampleMany (const QVector< QPointF > &xy, QVector< double > *outZ, qint64 maxBufBytes=kMaxReadBufBytesDefault) const
	Batch bilinear sampling at many DTM-CRS coordinates.
void	readPixels (const MapExtent &bbox, QVector< QPointF > &xyOut, QVector< double > &zOut) const
	Read every valid raster pixel whose centre falls within bbox.

Static Public Attributes
static constexpr qint64	kMaxReadBufBytesDefault = qint64(256) * 1024 * 1024
static constexpr qint64	kMaxGridBytesDefault = qint64(2048) * 1024 * 1024
static constexpr qint64	kMaxRetainedPointsDefault = 64ll * 1024 * 1024
static constexpr int	kMaxThinningHalo = 64

Detailed Description

Terrain-adaptive Steiner point selector from a DTM raster.

Usage:

mesh::DTMThinner thinner;
QVector<double> z;
if (thinner.open(dtmPath)) {
    const auto pts = thinner.generatePoints(domain, opts, &z);
    for (int i = 0; i < pts.size(); ++i) {
        mesh::SteinerPoint sp;
        sp.xy = pts[i]; sp.z = z[i]; sp.hasZ = true;
        gen.addSteinerPoint(sp);
    }
}

Constructor & Destructor Documentation

DTMThinner() [1/2]

mesh::DTMThinner::DTMThinner

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~DTMThinner()

mesh::DTMThinner::~DTMThinner

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DTMThinner() [2/2]

mesh::DTMThinner::DTMThinner ( const DTMThinner &  )

delete

Member Function Documentation

close()

void mesh::DTMThinner::close

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crsWkt()

QString mesh::DTMThinner::crsWkt

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const

errorMsg()

QString mesh::DTMThinner::errorMsg ( ) const

inline

generatePoints()

QVector< QPointF > mesh::DTMThinner::generatePoints	(	const MapExtent &	domain,
		const DTMThinnerOptions &	opts = {},
		QVector< double > *	outZ = nullptr,
		const DTMProgressFn &	progress = {},
		const DTMThinnerLimits &	limits = {}
	)		const

Generate terrain-significant sample points within domain.

Grids that exceed limits.maxGridBytes are processed in row bands with a halo (see file header "Scaling notes") — output is bit-identical to the untiled run for pass counts ≤ kMaxThinningHalo.

Parameters

domain	Meshing extent (same CRS as the DTM raster).
opts	Thinning parameters.
outZ	If non-null, filled with the exact DEM elevation for each returned point (parallel array). These values should be used directly — do NOT re-sample them from the DTM later.
progress	Optional progress/cancel callback (see DTMProgressFn).
limits	Resource ceilings — defaults are production values; exposed for tests.

Returns

(x, y) coordinates of retained terrain-feature vertices.

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isOpen()

bool mesh::DTMThinner::isOpen ( ) const

noexcept

open()

bool mesh::DTMThinner::open	(	const QString &	filePath,
		int	band = 1
	)

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operator=()

DTMThinner & mesh::DTMThinner::operator= ( const DTMThinner &  )

delete

pixelSize()

double mesh::DTMThinner::pixelSize

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const

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readPixels()

void mesh::DTMThinner::readPixels	(	const MapExtent &	bbox,
		QVector< QPointF > &	xyOut,
		QVector< double > &	zOut
	)		const

Read every valid raster pixel whose centre falls within bbox.

Issues a single bulk RasterIO call for the entire bounding box — far faster than calling sampleAt() per pixel. Pixel centres are reported in the raster's native map CRS (same as sampleAt()).

The caller is responsible for transforming the returned (x,y) to the mesh CRS if the two CRSs differ.

Regions whose output points would exceed the same ~2 GB working-set ceiling used by generatePoints() are refused up front: nothing is appended and the reason lands in errorMsg(). (A full-DEM bbox on a multi-GB raster would otherwise demand tens of GB and die at the Windows commit limit as an uncatchable-looking bad_alloc.)

Parameters

bbox	Axis-aligned bounding box in the raster's own CRS.
xyOut	Pixel-centre map coordinates (DTM CRS) — appended.
zOut	Corresponding elevation values — appended (parallel).

sampleAt()

double mesh::DTMThinner::sampleAt	(	double	x,
		double	y
	)		const

Sample the DTM at a single map-CRS coordinate. Returns NaN when out-of-bounds or NoData.

sampleMany()

void mesh::DTMThinner::sampleMany	(	const QVector< QPointF > &	xy,
		QVector< double > *	outZ,
		qint64	maxBufBytes = kMaxReadBufBytesDefault
	)		const

Batch bilinear sampling at many DTM-CRS coordinates.

outZ is resized to xy.size(); each entry equals what sampleAt() would return for that point (NaN when out-of-range, NoData in the 2×2 window, or on read failure). Queries are binned into raster row-strips sized to maxBufBytes and each strip is read with ONE RasterIO call (with a 1-row overlap so bilinear windows spanning a strip boundary resolve), instead of one RasterIO per point. Results are bit-identical to per-point sampleAt(). maxBufBytes is exposed for tests.

Member Data Documentation

kMaxGridBytesDefault

constexpr qint64 mesh::DTMThinner::kMaxGridBytesDefault = qint64(2048) * 1024 * 1024

staticconstexpr

Per-band grid working-set ceiling (~46 bytes per grid point).

kMaxReadBufBytesDefault

constexpr qint64 mesh::DTMThinner::kMaxReadBufBytesDefault = qint64(256) * 1024 * 1024

staticconstexpr

Raster scratch-buffer ceiling shared by the banded readers.

kMaxRetainedPointsDefault

constexpr qint64 mesh::DTMThinner::kMaxRetainedPointsDefault = 64ll * 1024 * 1024

staticconstexpr

Total retained-points ceiling across all bands (~64 M points).

kMaxThinningHalo

constexpr int mesh::DTMThinner::kMaxThinningHalo = 64

staticconstexpr

Maximum halo width — and therefore the per-band pass cap — in multi-band mode. "(unlimited)" passes are truncated to this.

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

• /home/runner/work/openswmm.gui/openswmm.gui/include/mesh/dtmthinner.h
• /home/runner/work/openswmm.gui/openswmm.gui/src/mesh/dtmthinner.cpp