qgscesiumimplicittiling.h

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/***************************************************************************
                         qgscesiumimplicittiling.h
                         -------------------------
    begin                : March 2026
    copyright            : (C) 2026 by Martin Dobias
    email                : wonder dot sk at gmail dot com
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#ifndef QGSCESIUMIMPLICITTILING_H
#define QGSCESIUMIMPLICITTILING_H
 
#include <nlohmann/json.hpp>
 
#include "qgis_core.h"
#include "qgstiledsceneboundingvolume.h"
 
#include <QBitArray>
#include <QUrl>
 
#define SIP_NO_FILE
 
class QgsTiledSceneNode;

class CORE_EXPORT QgsCesiumImplicitTiling
{
  public:
    struct TileCoordinate
    {
        int level = 0;
        int x = 0;
        int y = 0;
 
        auto operator<=>( const TileCoordinate & ) const = default;
        bool operator==( const TileCoordinate & ) const = default;
 
        friend inline size_t qHash( const TileCoordinate &c, size_t seed = 0 ) { return qHashMulti( seed, c.level, c.x, c.y ); }
    };

    struct Subtree
    {
        QBitArray tileAvailability;
        QBitArray contentAvailability;
        QBitArray childSubtreeAvailability;
    };

    struct Root
    {
        // definition of the tiling scheme

        int availableLevels = 0;
        int subtreeLevels = 0;
        QString contentUriTemplate;
        QString subtreeUriTemplate;
        QUrl baseUrl;
 
        // data related to the root node

        QgsTiledSceneBoundingVolume rootBoundingVolume;
        std::optional<QgsBox3D> rootRegion;
 
        double rootGeometricError = 0;
        Qgis::TileRefinementProcess refinementProcess = Qgis::TileRefinementProcess::Replacement;
        std::optional<QgsMatrix4x4> rootTransform;
        Qgis::Axis gltfUpAxis = Qgis::Axis::Y;
 
        QMap<TileCoordinate, Subtree> subtreeCache;
    };

    static bool parseImplicitTiling( const json &tileJson, QgsTiledSceneNode *newNode, const QUrl &baseUrl, Qgis::Axis gltfUpAxis, Root &tilingData );

    static Subtree parseSubtree( const Root &tilingData, const QByteArray &data );

    static QString expandTemplateUri( const QString &templateUri, const QUrl &baseUrl, const TileCoordinate &coord );

    static TileCoordinate tileCoordinateToParentSubtree( TileCoordinate coord, int subtreeLevels );

    static QMap<TileCoordinate, QgsTiledSceneNode *> createImplicitTilingChildren(
      QgsTiledSceneNode *node, const TileCoordinate &coord, Root &tilingData, const TileCoordinate &subtreeCoord, QgsCoordinateTransformContext &transformContext, long long &nextTileId
    );

    static Qgis::TileChildrenAvailability childAvailability( const Root &tilingData, const TileCoordinate &coord );

    static int subtreeBitIndex( int localLevel, int localX, int localY );
 
  private:
    static int subtreeTileCount( int levels );
    static int mortonIndex( int x, int y );
    static QgsTiledSceneBoundingVolume computeImplicitBoundingVolume( const QgsTiledSceneBoundingVolume &rootVolume, const TileCoordinate &coord );
    static QgsBox3D computeImplicitRegionBoundingVolume( const QgsBox3D &rootRegion, const TileCoordinate &coord );
};
 
#endif // QGSCESIUMIMPLICITTILING_H