qgs3dutils.cpp

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/***************************************************************************
  qgs3dutils.cpp
  --------------------------------------
  Date                 : July 2017
  Copyright            : (C) 2017 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.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgs3dutils.h"
 
#include "qgslinestring.h"
#include "qgspolygon.h"
#include "qgsfeaturerequest.h"
#include "qgsfeatureiterator.h"
#include "qgsfeature.h"
#include "qgsabstractgeometry.h"
#include "qgsvectorlayer.h"
#include "qgsexpressioncontextutils.h"
#include "qgsfeedback.h"
#include "qgsoffscreen3dengine.h"
#include "qgs3dmapscene.h"
#include "qgsabstract3dengine.h"
#include "qgsterraingenerator.h"
#include "qgscameracontroller.h"
#include "qgschunkedentity_p.h"
#include "qgsterrainentity_p.h"
#include "qgsraycastingutils_p.h"
 
#include "qgsline3dsymbol.h"
#include "qgspoint3dsymbol.h"
#include "qgspolygon3dsymbol.h"
 
#include "qgspointcloudrenderer.h"
#include "qgspointcloud3dsymbol.h"
#include "qgspointcloudlayer3drenderer.h"
#include "qgspointcloudrgbrenderer.h"
#include "qgspointcloudattributebyramprenderer.h"
#include "qgspointcloudclassifiedrenderer.h"
 
#include <QtMath>
#include <Qt3DExtras/QPhongMaterial>
#include <Qt3DRender/QRenderSettings>
 
// declared here as Qgs3DTypes has no cpp file
const char *Qgs3DTypes::PROP_NAME_3D_RENDERER_FLAG = "PROP_NAME_3D_RENDERER_FLAG";
 
QImage Qgs3DUtils::captureSceneImage( QgsAbstract3DEngine &engine, Qgs3DMapScene *scene )
{
  QImage resImage;
  QEventLoop evLoop;
 
  // We need to change render policy to RenderPolicy::Always, since otherwise render capture node won't work
  engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::Always );
 
  auto requestImageFcn = [&engine, scene]
  {
    if ( scene->sceneState() == Qgs3DMapScene::Ready )
    {
      engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
      engine.requestCaptureImage();
    }
  };
 
  auto saveImageFcn = [&evLoop, &resImage]( const QImage & img )
  {
    resImage = img;
    evLoop.quit();
  };
 
  const QMetaObject::Connection conn1 = QObject::connect( &engine, &QgsAbstract3DEngine::imageCaptured, saveImageFcn );
  QMetaObject::Connection conn2;
 
  if ( scene->sceneState() == Qgs3DMapScene::Ready )
  {
    requestImageFcn();
  }
  else
  {
    // first wait until scene is loaded
    conn2 = QObject::connect( scene, &Qgs3DMapScene::sceneStateChanged, requestImageFcn );
  }
 
  evLoop.exec();
 
  QObject::disconnect( conn1 );
  if ( conn2 )
    QObject::disconnect( conn2 );
 
  engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
  return resImage;
}
 
QImage Qgs3DUtils::captureSceneDepthBuffer( QgsAbstract3DEngine &engine, Qgs3DMapScene *scene )
{
  QImage resImage;
  QEventLoop evLoop;
 
  // We need to change render policy to RenderPolicy::Always, since otherwise render capture node won't work
  engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::Always );
 
  auto requestImageFcn = [&engine, scene]
  {
    if ( scene->sceneState() == Qgs3DMapScene::Ready )
    {
      engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
      engine.requestDepthBufferCapture();
    }
  };
 
  auto saveImageFcn = [&evLoop, &resImage]( const QImage & img )
  {
    resImage = img;
    evLoop.quit();
  };
 
  QMetaObject::Connection conn1 = QObject::connect( &engine, &QgsAbstract3DEngine::depthBufferCaptured, saveImageFcn );
  QMetaObject::Connection conn2;
 
  if ( scene->sceneState() == Qgs3DMapScene::Ready )
  {
    requestImageFcn();
  }
  else
  {
    // first wait until scene is loaded
    conn2 = QObject::connect( scene, &Qgs3DMapScene::sceneStateChanged, requestImageFcn );
  }
 
  evLoop.exec();
 
  QObject::disconnect( conn1 );
  if ( conn2 )
    QObject::disconnect( conn2 );
 
  engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::OnDemand );
  return resImage;
}
 
bool Qgs3DUtils::exportAnimation( const Qgs3DAnimationSettings &animationSettings,
                                  Qgs3DMapSettings &mapSettings,
                                  int framesPerSecond,
                                  const QString &outputDirectory,
                                  const QString &fileNameTemplate,
                                  const QSize &outputSize,
                                  QString &error,
                                  QgsFeedback *feedback
                                )
{
  if ( animationSettings.keyFrames().size() < 2 )
  {
    error = QObject::tr( "Unable to export 3D animation. Add at least 2 keyframes" );
    return false;
  }
 
  const float duration = animationSettings.duration(); //in seconds
  if ( duration <= 0 )
  {
    error = QObject::tr( "Unable to export 3D animation (invalid duration)." );
    return false;
  }
 
  float time = 0;
  int frameNo = 0;
  const int totalFrames = static_cast<int>( duration * framesPerSecond );
 
  if ( fileNameTemplate.isEmpty() )
  {
    error = QObject::tr( "Filename template is empty" );
    return false;
  }
 
  const int numberOfDigits = fileNameTemplate.count( QLatin1Char( '#' ) );
  if ( numberOfDigits < 0 )
  {
    error = QObject::tr( "Wrong filename template format (must contain #)" );
    return false;
  }
  const QString token( numberOfDigits, QLatin1Char( '#' ) );
  if ( !fileNameTemplate.contains( token ) )
  {
    error = QObject::tr( "Filename template must contain all # placeholders in one continuous group." );
    return false;
  }
 
  if ( !QDir().exists( outputDirectory ) )
  {
    if ( !QDir().mkpath( outputDirectory ) )
    {
      error = QObject::tr( "Output directory could not be created." );
      return false;
    }
  }
 
  QgsOffscreen3DEngine engine;
  engine.setSize( outputSize );
  Qgs3DMapScene *scene = new Qgs3DMapScene( mapSettings, &engine );
  engine.setRootEntity( scene );
  // We need to change render policy to RenderPolicy::Always, since otherwise render capture node won't work
  engine.renderSettings()->setRenderPolicy( Qt3DRender::QRenderSettings::RenderPolicy::Always );
 
  while ( time <= duration )
  {
 
    if ( feedback )
    {
      if ( feedback->isCanceled() )
      {
        error = QObject::tr( "Export canceled" );
        return false;
      }
      feedback->setProgress( frameNo / static_cast<double>( totalFrames ) * 100 );
    }
    ++frameNo;
 
    const Qgs3DAnimationSettings::Keyframe kf = animationSettings.interpolate( time );
    scene->cameraController()->setLookingAtPoint( kf.point, kf.dist, kf.pitch, kf.yaw );
 
    QString fileName( fileNameTemplate );
    const QString frameNoPaddedLeft( QStringLiteral( "%1" ).arg( frameNo, numberOfDigits, 10, QChar( '0' ) ) ); // e.g. 0001
    fileName.replace( token, frameNoPaddedLeft );
    const QString path = QDir( outputDirectory ).filePath( fileName );
 
    const QImage img = Qgs3DUtils::captureSceneImage( engine, scene );
 
    img.save( path );
 
    time += 1.0f / static_cast<float>( framesPerSecond );
  }
 
  return true;
}
 
 
int Qgs3DUtils::maxZoomLevel( double tile0width, double tileResolution, double maxError )
{
  if ( maxError <= 0 || tileResolution <= 0 || tile0width <= 0 )
    return 0;  // invalid input
 
  // derived from:
  // tile width [map units] = tile0width / 2^zoomlevel
  // tile error [map units] = tile width / tile resolution
  // + re-arranging to get zoom level if we know tile error we want to get
  const double zoomLevel = -log( tileResolution * maxError / tile0width ) / log( 2 );
  return round( zoomLevel );  // we could use ceil() here if we wanted to always get to the desired error
}
 
QString Qgs3DUtils::altClampingToString( Qgis::AltitudeClamping altClamp )
{
  switch ( altClamp )
  {
    case Qgis::AltitudeClamping::Absolute:
      return QStringLiteral( "absolute" );
    case Qgis::AltitudeClamping::Relative:
      return QStringLiteral( "relative" );
    case Qgis::AltitudeClamping::Terrain:
      return QStringLiteral( "terrain" );
  }
  BUILTIN_UNREACHABLE
}
 
 
Qgis::AltitudeClamping Qgs3DUtils::altClampingFromString( const QString &str )
{
  if ( str == QLatin1String( "absolute" ) )
    return Qgis::AltitudeClamping::Absolute;
  else if ( str == QLatin1String( "terrain" ) )
    return Qgis::AltitudeClamping::Terrain;
  else   // "relative"  (default)
    return Qgis::AltitudeClamping::Relative;
}
 
 
QString Qgs3DUtils::altBindingToString( Qgis::AltitudeBinding altBind )
{
  switch ( altBind )
  {
    case Qgis::AltitudeBinding::Vertex:
      return QStringLiteral( "vertex" );
    case Qgis::AltitudeBinding::Centroid:
      return QStringLiteral( "centroid" );
  }
  BUILTIN_UNREACHABLE
}
 
 
Qgis::AltitudeBinding Qgs3DUtils::altBindingFromString( const QString &str )
{
  if ( str == QLatin1String( "vertex" ) )
    return Qgis::AltitudeBinding::Vertex;
  else  // "centroid"  (default)
    return Qgis::AltitudeBinding::Centroid;
}
 
QString Qgs3DUtils::cullingModeToString( Qgs3DTypes::CullingMode mode )
{
  switch ( mode )
  {
    case Qgs3DTypes::NoCulling:
      return QStringLiteral( "no-culling" );
    case Qgs3DTypes::Front:
      return QStringLiteral( "front" );
    case Qgs3DTypes::Back:
      return QStringLiteral( "back" );
    case Qgs3DTypes::FrontAndBack:
      return QStringLiteral( "front-and-back" );
  }
  BUILTIN_UNREACHABLE
}
 
Qgs3DTypes::CullingMode Qgs3DUtils::cullingModeFromString( const QString &str )
{
  if ( str == QLatin1String( "front" ) )
    return Qgs3DTypes::Front;
  else if ( str == QLatin1String( "back" ) )
    return Qgs3DTypes::Back;
  else if ( str == QLatin1String( "front-and-back" ) )
    return Qgs3DTypes::FrontAndBack;
  else
    return Qgs3DTypes::NoCulling;
}
 
float Qgs3DUtils::clampAltitude( const QgsPoint &p, Qgis::AltitudeClamping altClamp, Qgis::AltitudeBinding altBind, float height, const QgsPoint &centroid, const Qgs3DMapSettings &map )
{
  float terrainZ = 0;
  switch ( altClamp )
  {
    case Qgis::AltitudeClamping::Relative:
    case Qgis::AltitudeClamping::Terrain:
    {
      const QgsPointXY pt = altBind == Qgis::AltitudeBinding::Vertex ? p : centroid;
      terrainZ = map.terrainRenderingEnabled() && map.terrainGenerator() ? map.terrainGenerator()->heightAt( pt.x(), pt.y(), map ) : 0;
      break;
    }
 
    case Qgis::AltitudeClamping::Absolute:
      break;
  }
 
  float geomZ = 0;
  if ( p.is3D() )
  {
    switch ( altClamp )
    {
      case Qgis::AltitudeClamping::Absolute:
      case Qgis::AltitudeClamping::Relative:
        geomZ = p.z();
        break;
 
      case Qgis::AltitudeClamping::Terrain:
        break;
    }
  }
 
  const float z = ( terrainZ + geomZ ) * map.terrainVerticalScale() + height;
  return z;
}
 
void Qgs3DUtils::clampAltitudes( QgsLineString *lineString, Qgis::AltitudeClamping altClamp, Qgis::AltitudeBinding altBind, const QgsPoint &centroid, float height, const Qgs3DMapSettings &map )
{
  for ( int i = 0; i < lineString->nCoordinates(); ++i )
  {
    float terrainZ = 0;
    switch ( altClamp )
    {
      case Qgis::AltitudeClamping::Relative:
      case Qgis::AltitudeClamping::Terrain:
      {
        QgsPointXY pt;
        switch ( altBind )
        {
          case Qgis::AltitudeBinding::Vertex:
            pt.setX( lineString->xAt( i ) );
            pt.setY( lineString->yAt( i ) );
            break;
 
          case Qgis::AltitudeBinding::Centroid:
            pt.set( centroid.x(), centroid.y() );
            break;
        }
 
        terrainZ = map.terrainRenderingEnabled() && map.terrainGenerator() ? map.terrainGenerator()->heightAt( pt.x(), pt.y(), map ) : 0;
        break;
      }
 
      case Qgis::AltitudeClamping::Absolute:
        break;
    }
 
    float geomZ = 0;
 
    switch ( altClamp )
    {
      case Qgis::AltitudeClamping::Absolute:
      case Qgis::AltitudeClamping::Relative:
        geomZ = lineString->zAt( i );
        break;
 
      case Qgis::AltitudeClamping::Terrain:
        break;
    }
 
    const float z = ( terrainZ + geomZ ) * map.terrainVerticalScale() + height;
    lineString->setZAt( i, z );
  }
}
 
 
bool Qgs3DUtils::clampAltitudes( QgsPolygon *polygon, Qgis::AltitudeClamping altClamp, Qgis::AltitudeBinding altBind, float height, const Qgs3DMapSettings &map )
{
  if ( !polygon->is3D() )
    polygon->addZValue( 0 );
 
  QgsPoint centroid;
  switch ( altBind )
  {
    case Qgis::AltitudeBinding::Vertex:
      break;
 
    case Qgis::AltitudeBinding::Centroid:
      centroid = polygon->centroid();
      break;
  }
 
  QgsCurve *curve = const_cast<QgsCurve *>( polygon->exteriorRing() );
  QgsLineString *lineString = qgsgeometry_cast<QgsLineString *>( curve );
  if ( !lineString )
    return false;
 
  clampAltitudes( lineString, altClamp, altBind, centroid, height, map );
 
  for ( int i = 0; i < polygon->numInteriorRings(); ++i )
  {
    QgsCurve *curve = const_cast<QgsCurve *>( polygon->interiorRing( i ) );
    QgsLineString *lineString = qgsgeometry_cast<QgsLineString *>( curve );
    if ( !lineString )
      return false;
 
    clampAltitudes( lineString, altClamp, altBind, centroid, height, map );
  }
  return true;
}
 
 
QString Qgs3DUtils::matrix4x4toString( const QMatrix4x4 &m )
{
  const float *d = m.constData();
  QStringList elems;
  elems.reserve( 16 );
  for ( int i = 0; i < 16; ++i )
    elems << QString::number( d[i] );
  return elems.join( ' ' );
}
 
QMatrix4x4 Qgs3DUtils::stringToMatrix4x4( const QString &str )
{
  QMatrix4x4 m;
  float *d = m.data();
  QStringList elems = str.split( ' ' );
  for ( int i = 0; i < 16; ++i )
    d[i] = elems[i].toFloat();
  return m;
}
 
void Qgs3DUtils::extractPointPositions( const QgsFeature &f, const Qgs3DMapSettings &map, Qgis::AltitudeClamping altClamp, QVector<QVector3D> &positions )
{
  const QgsAbstractGeometry *g = f.geometry().constGet();
  for ( auto it = g->vertices_begin(); it != g->vertices_end(); ++it )
  {
    const QgsPoint pt = *it;
    float geomZ = 0;
    if ( pt.is3D() )
    {
      geomZ = pt.z();
    }
    const float terrainZ = map.terrainRenderingEnabled() && map.terrainGenerator() ? map.terrainGenerator()->heightAt( pt.x(), pt.y(), map ) * map.terrainVerticalScale() : 0;
    float h = 0.0f;
    switch ( altClamp )
    {
      case Qgis::AltitudeClamping::Absolute:
        h = geomZ;
        break;
      case Qgis::AltitudeClamping::Terrain:
        h = terrainZ;
        break;
      case Qgis::AltitudeClamping::Relative:
        h = terrainZ + geomZ;
        break;
    }
    positions.append( QVector3D( pt.x() - map.origin().x(), h, -( pt.y() - map.origin().y() ) ) );
    QgsDebugMsgLevel( QStringLiteral( "%1 %2 %3" ).arg( positions.last().x() ).arg( positions.last().y() ).arg( positions.last().z() ), 2 );
  }
}
 
static inline uint outcode( QVector4D v )
{
  // For a discussion of outcodes see pg 388 Dunn & Parberry.
  // For why you can't just test if the point is in a bounding box
  // consider the case where a view frustum with view-size 1.5 x 1.5
  // is tested against a 2x2 box which encloses the near-plane, while
  // all the points in the box are outside the frustum.
  // TODO: optimise this with assembler - according to D&P this can
  // be done in one line of assembler on some platforms
  uint code = 0;
  if ( v.x() < -v.w() ) code |= 0x01;
  if ( v.x() > v.w() )  code |= 0x02;
  if ( v.y() < -v.w() ) code |= 0x04;
  if ( v.y() > v.w() )  code |= 0x08;
  if ( v.z() < -v.w() ) code |= 0x10;
  if ( v.z() > v.w() )  code |= 0x20;
  return code;
}
 
 
bool Qgs3DUtils::isCullable( const QgsAABB &bbox, const QMatrix4x4 &viewProjectionMatrix )
{
  uint out = 0xff;
 
  for ( int i = 0; i < 8; ++i )
  {
    const QVector4D p( ( ( i >> 0 ) & 1 ) ? bbox.xMin : bbox.xMax,
                       ( ( i >> 1 ) & 1 ) ? bbox.yMin : bbox.yMax,
                       ( ( i >> 2 ) & 1 ) ? bbox.zMin : bbox.zMax, 1 );
    const QVector4D pc = viewProjectionMatrix * p;
 
    // if the logical AND of all the outcodes is non-zero then the BB is
    // definitely outside the view frustum.
    out = out & outcode( pc );
  }
  return out;
}
 
QgsVector3D Qgs3DUtils::mapToWorldCoordinates( const QgsVector3D &mapCoords, const QgsVector3D &origin )
{
  return QgsVector3D( mapCoords.x() - origin.x(),
                      mapCoords.z() - origin.z(),
                      -( mapCoords.y() - origin.y() ) );
 
}
 
QgsVector3D Qgs3DUtils::worldToMapCoordinates( const QgsVector3D &worldCoords, const QgsVector3D &origin )
{
  return QgsVector3D( worldCoords.x() + origin.x(),
                      -worldCoords.z() + origin.y(),
                      worldCoords.y() + origin.z() );
}
 
QgsRectangle Qgs3DUtils::tryReprojectExtent2D( const QgsRectangle &extent, const QgsCoordinateReferenceSystem &crs1, const QgsCoordinateReferenceSystem &crs2, const QgsCoordinateTransformContext &context )
{
  QgsRectangle extentMapCrs( extent );
  if ( crs1 != crs2 )
  {
    // reproject if necessary
    QgsCoordinateTransform ct( crs1, crs2, context );
    ct.setBallparkTransformsAreAppropriate( true );
    try
    {
      extentMapCrs = ct.transformBoundingBox( extentMapCrs );
    }
    catch ( const QgsCsException & )
    {
      // bad luck, can't reproject for some reason
      QgsDebugError( QStringLiteral( "3D utils: transformation of extent failed: " ) + extentMapCrs.toString( -1 ) );
    }
  }
  return extentMapCrs;
}
 
QgsAABB Qgs3DUtils::layerToWorldExtent( const QgsRectangle &extent, double zMin, double zMax, const QgsCoordinateReferenceSystem &layerCrs, const QgsVector3D &mapOrigin, const QgsCoordinateReferenceSystem &mapCrs, const QgsCoordinateTransformContext &context )
{
  const QgsRectangle extentMapCrs( Qgs3DUtils::tryReprojectExtent2D( extent, layerCrs, mapCrs, context ) );
  return mapToWorldExtent( extentMapCrs, zMin, zMax, mapOrigin );
}
 
QgsRectangle Qgs3DUtils::worldToLayerExtent( const QgsAABB &bbox, const QgsCoordinateReferenceSystem &layerCrs, const QgsVector3D &mapOrigin, const QgsCoordinateReferenceSystem &mapCrs, const QgsCoordinateTransformContext &context )
{
  const QgsRectangle extentMap = worldToMapExtent( bbox, mapOrigin );
  return Qgs3DUtils::tryReprojectExtent2D( extentMap, mapCrs, layerCrs, context );
}
 
QgsAABB Qgs3DUtils::mapToWorldExtent( const QgsRectangle &extent, double zMin, double zMax, const QgsVector3D &mapOrigin )
{
  const QgsVector3D extentMin3D( extent.xMinimum(), extent.yMinimum(), zMin );
  const QgsVector3D extentMax3D( extent.xMaximum(), extent.yMaximum(), zMax );
  const QgsVector3D worldExtentMin3D = mapToWorldCoordinates( extentMin3D, mapOrigin );
  const QgsVector3D worldExtentMax3D = mapToWorldCoordinates( extentMax3D, mapOrigin );
  QgsAABB rootBbox( worldExtentMin3D.x(), worldExtentMin3D.y(), worldExtentMin3D.z(),
                    worldExtentMax3D.x(), worldExtentMax3D.y(), worldExtentMax3D.z() );
  return rootBbox;
}
 
QgsRectangle Qgs3DUtils::worldToMapExtent( const QgsAABB &bbox, const QgsVector3D &mapOrigin )
{
  const QgsVector3D worldExtentMin3D = Qgs3DUtils::worldToMapCoordinates( QgsVector3D( bbox.xMin, bbox.yMin, bbox.zMin ), mapOrigin );
  const QgsVector3D worldExtentMax3D = Qgs3DUtils::worldToMapCoordinates( QgsVector3D( bbox.xMax, bbox.yMax, bbox.zMax ), mapOrigin );
  const QgsRectangle extentMap( worldExtentMin3D.x(), worldExtentMin3D.y(), worldExtentMax3D.x(), worldExtentMax3D.y() );
  // we discard zMin/zMax here because we don't need it
  return extentMap;
}
 
 
QgsVector3D Qgs3DUtils::transformWorldCoordinates( const QgsVector3D &worldPoint1, const QgsVector3D &origin1, const QgsCoordinateReferenceSystem &crs1, const QgsVector3D &origin2, const QgsCoordinateReferenceSystem &crs2, const QgsCoordinateTransformContext &context )
{
  const QgsVector3D mapPoint1 = worldToMapCoordinates( worldPoint1, origin1 );
  QgsVector3D mapPoint2 = mapPoint1;
  if ( crs1 != crs2 )
  {
    // reproject if necessary
    const QgsCoordinateTransform ct( crs1, crs2, context );
    try
    {
      const QgsPointXY pt = ct.transform( QgsPointXY( mapPoint1.x(), mapPoint1.y() ) );
      mapPoint2.set( pt.x(), pt.y(), mapPoint1.z() );
    }
    catch ( const QgsCsException & )
    {
      // bad luck, can't reproject for some reason
    }
  }
  return mapToWorldCoordinates( mapPoint2, origin2 );
}
 
void Qgs3DUtils::estimateVectorLayerZRange( QgsVectorLayer *layer, double &zMin, double &zMax )
{
  if ( !QgsWkbTypes::hasZ( layer->wkbType() ) )
  {
    zMin = 0;
    zMax = 0;
    return;
  }
 
  zMin = std::numeric_limits<double>::max();
  zMax = std::numeric_limits<double>::lowest();
 
  QgsFeature f;
  QgsFeatureIterator it = layer->getFeatures( QgsFeatureRequest().setNoAttributes().setLimit( 100 ) );
  while ( it.nextFeature( f ) )
  {
    const QgsGeometry g = f.geometry();
    for ( auto vit = g.vertices_begin(); vit != g.vertices_end(); ++vit )
    {
      const double z = ( *vit ).z();
      if ( z < zMin ) zMin = z;
      if ( z > zMax ) zMax = z;
    }
  }
 
  if ( zMin == std::numeric_limits<double>::max() && zMax == std::numeric_limits<double>::lowest() )
  {
    zMin = 0;
    zMax = 0;
  }
}
 
QgsExpressionContext Qgs3DUtils::globalProjectLayerExpressionContext( QgsVectorLayer *layer )
{
  QgsExpressionContext exprContext;
  exprContext << QgsExpressionContextUtils::globalScope()
              << QgsExpressionContextUtils::projectScope( QgsProject::instance() )
              << QgsExpressionContextUtils::layerScope( layer );
  return exprContext;
}
 
QgsPhongMaterialSettings Qgs3DUtils::phongMaterialFromQt3DComponent( Qt3DExtras::QPhongMaterial *material )
{
  QgsPhongMaterialSettings settings;
  settings.setAmbient( material->ambient() );
  settings.setDiffuse( material->diffuse() );
  settings.setSpecular( material->specular() );
  settings.setShininess( material->shininess() );
  return settings;
}
 
QgsRay3D Qgs3DUtils::rayFromScreenPoint( const QPoint &point, const QSize &windowSize, Qt3DRender::QCamera *camera )
{
  const QVector3D deviceCoords( point.x(), point.y(), 0.0 );
  // normalized device coordinates
  const QVector3D normDeviceCoords( 2.0 * deviceCoords.x() / windowSize.width() - 1.0f, 1.0f - 2.0 * deviceCoords.y() / windowSize.height(), camera->nearPlane() );
  // clip coordinates
  const QVector4D rayClip( normDeviceCoords.x(), normDeviceCoords.y(), -1.0, 0.0 );
 
  const QMatrix4x4 invertedProjMatrix = camera->projectionMatrix().inverted();
  const QMatrix4x4 invertedViewMatrix = camera->viewMatrix().inverted();
 
  // ray direction in view coordinates
  QVector4D rayDirView = invertedProjMatrix * rayClip;
  // ray origin in world coordinates
  const QVector4D rayOriginWorld = invertedViewMatrix * QVector4D( 0.0f, 0.0f, 0.0f, 1.0f );
 
  // ray direction in world coordinates
  rayDirView.setZ( -1.0f );
  rayDirView.setW( 0.0f );
  const QVector4D rayDirWorld4D = invertedViewMatrix * rayDirView;
  QVector3D rayDirWorld( rayDirWorld4D.x(), rayDirWorld4D.y(), rayDirWorld4D.z() );
  rayDirWorld = rayDirWorld.normalized();
 
  return QgsRay3D( QVector3D( rayOriginWorld ), rayDirWorld );
}
 
QVector3D Qgs3DUtils::screenPointToWorldPos( const QPoint &screenPoint, double depth, const QSize &screenSize, Qt3DRender::QCamera *camera )
{
  double dNear = camera->nearPlane();
  double dFar = camera->farPlane();
  double distance = ( 2.0 * dNear * dFar ) / ( dFar + dNear - ( depth * 2 - 1 ) * ( dFar - dNear ) );
 
  QgsRay3D ray = Qgs3DUtils::rayFromScreenPoint( screenPoint, screenSize, camera );
  double dot = QVector3D::dotProduct( ray.direction(), camera->viewVector().normalized() );
  distance /= dot;
 
  return ray.origin() + distance * ray.direction();
}
 
void Qgs3DUtils::pitchAndYawFromViewVector( QVector3D vect, double &pitch, double &yaw )
{
  vect.normalize();
 
  pitch = qRadiansToDegrees( qAcos( vect.y() ) );
  yaw = qRadiansToDegrees( qAtan2( -vect.z(), vect.x() ) ) + 90;
}
 
QVector2D Qgs3DUtils::screenToTextureCoordinates( QVector2D screenXY, QSize winSize )
{
  return QVector2D( screenXY.x() / winSize.width(), 1 - screenXY.y() / winSize.width() );
}
 
QVector2D Qgs3DUtils::textureToScreenCoordinates( QVector2D textureXY, QSize winSize )
{
  return QVector2D( textureXY.x() * winSize.width(), ( 1 - textureXY.y() ) * winSize.height() );
}
 
std::unique_ptr<QgsPointCloudLayer3DRenderer> Qgs3DUtils::convert2DPointCloudRendererTo3D( QgsPointCloudRenderer *renderer )
{
  if ( !renderer )
    return nullptr;
 
  std::unique_ptr< QgsPointCloud3DSymbol > symbol3D;
  if ( renderer->type() == QLatin1String( "ramp" ) )
  {
    const QgsPointCloudAttributeByRampRenderer *renderer2D = dynamic_cast< const QgsPointCloudAttributeByRampRenderer * >( renderer );
    symbol3D = std::make_unique< QgsColorRampPointCloud3DSymbol >();
    QgsColorRampPointCloud3DSymbol *symbol = static_cast< QgsColorRampPointCloud3DSymbol * >( symbol3D.get() );
    symbol->setAttribute( renderer2D->attribute() );
    symbol->setColorRampShaderMinMax( renderer2D->minimum(), renderer2D->maximum() );
    symbol->setColorRampShader( renderer2D->colorRampShader() );
  }
  else if ( renderer->type() == QLatin1String( "rgb" ) )
  {
    const QgsPointCloudRgbRenderer *renderer2D = dynamic_cast< const QgsPointCloudRgbRenderer * >( renderer );
    symbol3D = std::make_unique< QgsRgbPointCloud3DSymbol >();
    QgsRgbPointCloud3DSymbol *symbol = static_cast< QgsRgbPointCloud3DSymbol * >( symbol3D.get() );
    symbol->setRedAttribute( renderer2D->redAttribute() );
    symbol->setGreenAttribute( renderer2D->greenAttribute() );
    symbol->setBlueAttribute( renderer2D->blueAttribute() );
 
    symbol->setRedContrastEnhancement( renderer2D->redContrastEnhancement() ? new QgsContrastEnhancement( *renderer2D->redContrastEnhancement() ) : nullptr );
    symbol->setGreenContrastEnhancement( renderer2D->greenContrastEnhancement() ? new QgsContrastEnhancement( *renderer2D->greenContrastEnhancement() ) : nullptr );
    symbol->setBlueContrastEnhancement( renderer2D->blueContrastEnhancement() ? new QgsContrastEnhancement( *renderer2D->blueContrastEnhancement() ) : nullptr );
  }
  else if ( renderer->type() == QLatin1String( "classified" ) )
  {
 
    const QgsPointCloudClassifiedRenderer *renderer2D = dynamic_cast< const QgsPointCloudClassifiedRenderer * >( renderer );
    symbol3D = std::make_unique< QgsClassificationPointCloud3DSymbol >();
    QgsClassificationPointCloud3DSymbol *symbol = static_cast< QgsClassificationPointCloud3DSymbol * >( symbol3D.get() );
    symbol->setAttribute( renderer2D->attribute() );
    symbol->setCategoriesList( renderer2D->categories() );
  }
 
  if ( symbol3D )
  {
    std::unique_ptr< QgsPointCloudLayer3DRenderer > renderer3D = std::make_unique< QgsPointCloudLayer3DRenderer >();
    renderer3D->setSymbol( symbol3D.release() );
    return renderer3D;
  }
  return nullptr;
}
 
QHash<QgsMapLayer *, QVector<QgsRayCastingUtils::RayHit>> Qgs3DUtils::castRay( Qgs3DMapScene *scene, const QgsRay3D &ray, const QgsRayCastingUtils::RayCastContext &context )
{
  QgsRayCastingUtils::Ray3D r( ray.origin(), ray.direction(), context.maxDistance );
  QHash<QgsMapLayer *, QVector<QgsRayCastingUtils:: RayHit>> results;
  const QList<QgsMapLayer *> keys = scene->layers();
  for ( QgsMapLayer *layer : keys )
  {
    Qt3DCore::QEntity *entity = scene->layerEntity( layer );
 
    if ( QgsChunkedEntity *chunkedEntity = qobject_cast<QgsChunkedEntity *>( entity ) )
    {
      const QVector<QgsRayCastingUtils::RayHit> result = chunkedEntity->rayIntersection( r, context );
      if ( !result.isEmpty() )
        results[ layer ] = result;
    }
  }
  if ( QgsTerrainEntity *terrain = scene->terrainEntity() )
  {
    const QVector<QgsRayCastingUtils::RayHit> result = terrain->rayIntersection( r, context );
    if ( !result.isEmpty() )
      results[ nullptr ] = result;  // Terrain hits are not tied to a layer so we use nullptr as their key here
  }
  return results;
}
 
float Qgs3DUtils::screenSpaceError( float epsilon, float distance, float screenSize, float fov )
{
  /* This routine approximately calculates how an error (epsilon) of an object in world coordinates
   * at given distance (between camera and the object) will look like in screen coordinates.
   *
   * the math below simply uses triangle similarity:
   *
   *             epsilon                       phi
   *   -----------------------------  = ----------------
   *   [ frustum width at distance ]    [ screen width ]
   *
   * Then we solve for phi, substituting [frustum width at distance] = 2 * distance * tan(fov / 2)
   *
   *  ________xxx__      xxx = real world error (epsilon)
   *  \     |     /        x = screen space error (phi)
   *   \    |    /
   *    \___|_x_/   near plane (screen space)
   *     \  |  /
   *      \ | /
   *       \|/    angle = field of view
   *       camera
   */
  float phi = epsilon * screenSize / ( 2 * distance * tan( fov * M_PI / ( 2 * 180 ) ) );
  return phi;
}