HeightField.h

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/****************************************************************************
 *
 * (c) 2009-2024 QGROUNDCONTROL PROJECT <http://www.qgroundcontrol.org>
 *
 * QGroundControl is licensed according to the terms in the file
 * COPYING.md in the root of the source code directory.
 *
 ****************************************************************************/
 
#pragma once
 
#include <QtCore/QList>
#include <QtCore/QObject>
#include <QtCore/QPointF>
#include <QtCore/QRectF>
#include <QtQmlIntegration/QtQmlIntegration>
 
#include "ElevationTilePyramid.h"
#include "PatchSampler.h"
#include "TileMath.h"
 
class HeightField : public QObject
{
    Q_OBJECT
    // Passed through QML as an opaque pointer (PatchGeometry.heightField)
    QML_ANONYMOUS
 
public:
    explicit HeightField(QObject* parent = nullptr);
 
    static constexpr int kMaxGridSize = 4096;
 
    bool insertTile(const TileMath::TileKey& key, ElevationTilePyramid::Grid grid);
 
    void setPinnedKeys(QSet<TileMath::TileKey> keys) { _pyramid.setPinnedKeys(std::move(keys)); }
 
    double heightAt(const QPointF& world) const;
 
    QList<float> samplePatch(const TileMath::TileKey& key, int gridSize,
                             PatchSampler::EdgeStep* edgeStep = nullptr) const;
 
    int tileCount() const { return _pyramid.tileCount(); }
 
    bool hasTile(const TileMath::TileKey& key) const { return _pyramid.hasTile(key); }
 
    TileMath::TileKey backingKeyFor(const TileMath::TileKey& key) const
    {
        const ElevationTilePyramid::View view = _pyramid.bestTileFor(key);
        return view.isValid() ? view.key : TileMath::TileKey{0, 0, -1};
    }
 
    qint64 lookupCountForTest() const { return _pyramid.lookupCountForTest(); }
 
signals:
    void regionChanged(const QRectF& worldRect);
 
private:
    ElevationTilePyramid _pyramid;
 
    // Memoized last resolved view: adjacent sample positions almost always
    // resolve to the same stored tile, so heightAt reuses it when the query
    // key resolves to it (same arithmetic as the full lookup). Only populated
    // when the tile has no stored descendant (nothing finer could override
    // it), and invalidated on every insert (the view's grid pointer is only
    // valid until then).
    mutable ElevationTilePyramid::View _memoView;
    mutable double _memoMinX = 0.0;
    mutable double _memoMaxY = 0.0;
    mutable double _memoSpan = 0.0;
};