A 3D building viewer of OSM (OpenStreetMap) buildings map data.
This application demonstrates how to create 3D building geometry for display on a map using data from OpenStreetMap (OSM) servers or a locally limited data set when the server is unavailable.
The application uses a queue to handle concurrent requests to boost up the loading process of maps and building data.
OSMRequest::OSMRequest(QObject *parent) : QObject{parent} { connect( &m_queuesTimer, &QTimer::timeout, this, [this](){ if ( m_buildingsQueue.isEmpty() && m_mapsQueue.isEmpty() ) { m_queuesTimer.stop(); } else { #ifdef QT_DEBUG const int numConcurrentRequests = 1; #else const int numConcurrentRequests = 6; #endif if ( !m_buildingsQueue.isEmpty() && m_buildingsNumberOfRequestsInFlight < numConcurrentRequests ) { getBuildingsDataRequest(m_buildingsQueue.dequeue()); ++m_buildingsNumberOfRequestsInFlight; } if ( !m_mapsQueue.isEmpty() && m_mapsNumberOfRequestsInFlight < numConcurrentRequests ) { getMapsDataRequest(m_mapsQueue.dequeue()); ++m_mapsNumberOfRequestsInFlight; } } }); m_queuesTimer.setInterval(0);
A custom request handler class is implemented for fetching the data from the OSM building and map servers.
void OSMRequest::getBuildingsData(const QQueue<OSMTileData> &buildingsQueue) { if ( buildingsQueue.isEmpty() ) return; m_buildingsQueue = buildingsQueue; if ( !m_queuesTimer.isActive() ) m_queuesTimer.start(); } void OSMRequest::getBuildingsDataRequest(const OSMTileData &tile) { QString fileName = "data/" + QString::number(tile.ZoomLevel) + "," + QString::number(tile.TileX) + "," + QString::number(tile.TileY) + ".json"; QFileInfo file(fileName); if ( file.size() ) { QFile file(fileName); if (file.open(QFile::ReadOnly)){ QByteArray data = file.readAll(); file.close(); emit buildingsDataReady( importGeoJson(QJsonDocument::fromJson( data )), tile.TileX, tile.TileY, tile.ZoomLevel ); --m_buildingsNumberOfRequestsInFlight; return; } } QUrl url = QUrl(tr(m_uRL_OSMB_JSON).arg(QString::number(tile.ZoomLevel),QString::number(tile.TileX),QString::number(tile.TileY)) ); QNetworkReply * reply = m_networkAccessManager.get( QNetworkRequest(url)); connect( reply, &QNetworkReply::finished, this, [this, reply, tile, url](){ reply->deleteLater(); if ( reply->error() == QNetworkReply::NoError ) { QByteArray data = reply->readAll(); emit buildingsDataReady( importGeoJson(QJsonDocument::fromJson( data )), tile.TileX, tile.TileY, tile.ZoomLevel ); }else { qWarning() << "OSMRequest::getBuildingsData" << reply->error() << url; } --m_buildingsNumberOfRequestsInFlight; } ); void OSMRequest::getMapsData(const QQueue<OSMTileData> &mapsQueue) { if ( mapsQueue.isEmpty() ) return; m_mapsQueue = mapsQueue; if ( !m_queuesTimer.isActive() ) m_queuesTimer.start(); } void OSMRequest::getMapsDataRequest(const OSMTileData &tile) { QString fileName = "data/" + QString::number(tile.ZoomLevel) + "," + QString::number(tile.TileX) + "," + QString::number(tile.TileY) + ".png"; QFileInfo file(fileName); if ( file.size() ) { QFile file(fileName); if (file.open(QFile::ReadOnly)){ QByteArray data = file.readAll(); file.close(); emit mapsDataReady( data, tile.TileX, tile.TileY, tile.ZoomLevel ); --m_mapsNumberOfRequestsInFlight; return; } } QUrl url = QUrl(tr(m_uRL_OSMB_MAP).arg(QString::number(tile.ZoomLevel),QString::number(tile.TileX),QString::number(tile.TileY)) ); QNetworkReply * reply = m_networkAccessManager.get( QNetworkRequest(url)); connect( reply, &QNetworkReply::finished, this, [this, reply, tile, url](){ reply->deleteLater(); if ( reply->error() == QNetworkReply::NoError ) { QByteArray data = reply->readAll(); emit mapsDataReady( data, tile.TileX, tile.TileY, tile.ZoomLevel ); }else { qWarning() << "OSMRequest::getMapsDataRequest" << reply->error() << url; } --m_mapsNumberOfRequestsInFlight; } );
The application parses the online data to convert it to a QVariant list of keys and values in geo formats such as QGeoPolygon .
emit buildingsDataReady( importGeoJson(QJsonDocument::fromJson( data )), tile.TileX, tile.TileY, tile.ZoomLevel );
--m_buildingsNumberOfRequestsInFlight;
The parsed building data is sent to a custom geometry item to convert the geo coordinates to 3D coordinates.
constexpr auto convertGeoCoordToVertexPosition = [](const float lat, const float lon) -> QVector3D {
const double scale = 1.212;
const double geoToPositionScale = 1000000 * scale;
const double XOffsetFromCenter = 537277 * scale;
const double YOffsetFromCenter = 327957 * scale;
double x = (lon/360.0 + 0.5) * geoToPositionScale;
double y = (1.0-log(qTan(qDegreesToRadians(lat)) + 1.0 / qCos(qDegreesToRadians(lat))) / M_PI) * 0.5 * geoToPositionScale;
return QVector3D( x - XOffsetFromCenter, YOffsetFromCenter - y, 0.0 );
};
The required data for the index and vertex buffers, such as position, normals, tangents, and UV coordinates, is generated.
for ( const QVariant &baseData : geoVariantsList ) {
for ( const QVariant &dataValue : baseData.toMap()["data"].toList() ) {
auto featureMap = dataValue.toMap();
auto properties = featureMap["properties"].toMap();
auto buildingCoords = featureMap["data"].value<QGeoPolygon>().perimeter();
float height = 0.15 * properties["height"].toLongLong();
float levels = static_cast<float>(properties["levels"].toLongLong());
QColor color = QColor::fromString( properties["color"].toString());
if ( !color.isValid() || color == QColor::fromString("black") )
color = QColor("white");
QColor roofColor = QColor::fromString( properties["roofColor"].toString());
if ( !roofColor.isValid() || roofColor == QColor::fromString("black") )
roofColor = color;
QVector3D subsetMinBound = QVector3D(maxFloat, maxFloat, maxFloat);
QVector3D subsetMaxBound = QVector3D(minFloat, minFloat, minFloat);
qsizetype numSubsetVertices = buildingCoords.size() * 2;
qsizetype lastVertexDataCount = vertexData.size();
qsizetype lastIndexDataCount = indexData.size();
vertexData.resize( lastVertexDataCount + numSubsetVertices * strideVertex );
indexData.resize( lastIndexDataCount + ( numSubsetVertices - 2 ) * stridePermitive );
float *vbPtr = &reinterpret_cast<float *>(vertexData.data())[globalVertexCounter * striedVertexLen];
uint32_t *ibPtr = &reinterpret_cast<uint32_t *>(indexData.data())[globalPermitiveCounter * 3];
qsizetype subsetVertexCounter = 0;
QVector3D lastBaseVertexPos;
QVector3D lastExtrudedVertexPos;
QVector3D currentBaseVertexPos;
QVector3D currentExtrudedVertexPos;
QVector3D subsetPolygonCenter;
using PolygonVertex = std::array<double, 2>;
using PolygonVertices = std::vector<PolygonVertex>;
PolygonVertices roofPolygonVertices;
for ( const QGeoCoordinate &buildingPoint : buildingCoords ) {
...
std::vector<PolygonVertices> roofPolygonsVerices;
roofPolygonsVerices.push_back( roofPolygonVertices );
std::vector<uint32_t> roofIndices = mapbox::earcut<uint32_t>(roofPolygonsVerices);
lastVertexDataCount = vertexData.size();
lastIndexDataCount = indexData.size();
vertexData.resize( lastVertexDataCount + roofPolygonVertices.size() * strideVertex );
indexData.resize( lastIndexDataCount + roofIndices.size() * sizeof(uint32_t) );
vbPtr = &reinterpret_cast<float *>(vertexData.data())[globalVertexCounter * striedVertexLen];
ibPtr = &reinterpret_cast<uint32_t *>(indexData.data())[globalPermitiveCounter * 3];
for ( const uint32_t &roofIndex : roofIndices ) {
*ibPtr++ = roofIndex + globalVertexCounter;
}
qsizetype roofPermitiveCount = roofIndices.size() / 3;
globalPermitiveCounter += roofPermitiveCount;
for ( const PolygonVertex &polygonVertex : roofPolygonVertices ) {
//position
*vbPtr++ = polygonVertex.at(0);
*vbPtr++ = polygonVertex.at(1);
*vbPtr++ = height;
//normal
*vbPtr++ = 0.0;
*vbPtr++ = 0.0;
*vbPtr++ = 1.0;
//tangent
*vbPtr++ = 1.0;
*vbPtr++ = 0.0;
*vbPtr++ = 0.0;
//binormal
*vbPtr++ = 0.0;
*vbPtr++ = 1.0;
*vbPtr++ = 0.0;
//color/
*vbPtr++ = roofColor.redF();
*vbPtr++ = roofColor.greenF();
*vbPtr++ = roofColor.blueF();
*vbPtr++ = 1.0;
//texcoord
*vbPtr++ = 1.0;
*vbPtr++ = 1.0;
*vbPtr++ = 0.0;
*vbPtr++ = 1.0;
++subsetVertexCounter;
++globalVertexCounter;
}
}
}
}
}
clear();
The downloaded PNG data is sent to a custom QQuick3DTextureData item to convert the PNG format to a texture for map tiles.
void CustomTextureData::setImageData(const QByteArray &data) { QImage image = QImage::fromData(data).convertToFormat(QImage::Format_RGBA8888); setTextureData( QByteArray(reinterpret_cast<const char*>(image.constBits()), image.sizeInBytes()) ); setSize( image.size() ); setHasTransparency(false); setFormat(Format::RGBA8); }
The application uses camera position, orientation, zoom level, and tilt to find the nearest tiles in the view.
void OSMManager::setCameraProperties(const QVector3D &position, const QVector3D &right, float cameraZoom, float minimunZoom, float maximumZoom, float cameraTilt, float minimumTilt, float maxmumTilt) { float tiltFactor = (cameraTilt - minimumTilt) / qMax(maxmumTilt - minimumTilt, 1.0); float zoomFactor = (cameraZoom - minimunZoom) / qMax(maximumZoom - minimunZoom, 1.0); QVector3D forwardVector = QVector3D::crossProduct(right, QVector3D(0.0, 0.0, -1.0)).normalized(); //Forward vector align to the XY plane QVector3D projectionOfForwardOnXY = position + forwardVector * tiltFactor * zoomFactor * 50.0; QQueue<OSMTileData> queue; for ( int fowardIndex = -20; fowardIndex <= 20; ++fowardIndex ){ for ( int sidewardIndex = -20; sidewardIndex <= 20; ++sidewardIndex ){ QVector3D transferedPosition = projectionOfForwardOnXY + QVector3D(float(m_tileSizeX * sidewardIndex) , float(m_tileSizeY * fowardIndex), 0.0); addBuildingRequestToQueue(queue, m_startBuildingTileX + int(transferedPosition.x() / m_tileSizeX), m_startBuildingTileY - int(transferedPosition.y() / m_tileSizeY)); } } int projectedTileX = m_startBuildingTileX + int(projectionOfForwardOnXY.x() / m_tileSizeX); int projectedTileY = m_startBuildingTileY - int(projectionOfForwardOnXY.y() / m_tileSizeY); std::sort(queue.begin(), queue.end(), [projectedTileX, projectedTileY](const OSMTileData &v1, const OSMTileData &v2)->bool{ return qSqrt(qPow(v1.TileX - projectedTileX, 2) + qPow(v1.TileY - projectedTileY, 2)) < qSqrt(qPow(v2.TileX - projectedTileX, 2) + qPow(v2.TileY - projectedTileY, 2)); }); m_request->getBuildingsData( queue ); m_request->getMapsData( queue );
Generates the tiles request queue.
void OSMManager::addBuildingRequestToQueue(QQueue<OSMTileData> &queue, int tileX, int tileY, int zoomLevel) { QString key = QString::number(tileX) + "," + QString::number(tileY) + "," + QString::number(zoomLevel); if ( m_buildingsHash.contains( key ) ) return; OSMTileData tile; tile.ZoomLevel = zoomLevel; tile.TileX = tileX; tile.TileY = tileY; queue.append( tile ); }
When you run the application, use the following controls for navigation.
| Windows | Android | |
|---|---|---|
| Pan | Left mouse button + drag | Drag |
| Zoom | Mouse wheel | Pinch |
| Rotate | Right mouse button + drag | n/a |
OSMCameraController {
id: cameraController
origin: originNode
camera: cameraNode
}
Every chunk of the map tile consists of a QML model (the 3D geometry) and a custom material which uses a rectangle as a base to render the tilemap texture.
...
id: chunkModelMap
Node {
property variant mapData: null
property int tileX: 0
property int tileY: 0
property int zoomLevel: 0
Model {
id: basePlane
position: Qt.vector3d( osmManager.tileSizeX * tileX, osmManager.tileSizeY * -tileY, 0.0 )
scale: Qt.vector3d( osmManager.tileSizeX / 100., osmManager.tileSizeY / 100., 0.5)
source: "#Rectangle"
materials: [
CustomMaterial {
property TextureInput tileTexture: TextureInput {
enabled: true
texture: Texture {
textureData: CustomTextureData {
Component.onCompleted: setImageData( mapData )
} }
}
shadingMode: CustomMaterial.Shaded
cullMode: Material.BackFaceCulling
fragmentShader: "customshadertiles.frag"
}
]
}
The application uses custom geometry to render tile buildings.
...
id: chunkModelBuilding
Node {
property variant geoVariantsList: null
property int tileX: 0
property int tileY: 0
property int zoomLevel: 0
Model {
id: model
scale: Qt.vector3d(1, 1, 1)
OSMGeometry {
id: osmGeometry
Component.onCompleted: updateData( geoVariantsList )
onGeometryReady:{
model.geometry = osmGeometry
}
}
materials: [
CustomMaterial {
shadingMode: CustomMaterial.Shaded
cullMode: Material.BackFaceCulling
vertexShader: "customshaderbuildings.vert"
fragmentShader: "customshaderbuildings.frag"
}
]
}
To render building parts such as rooftops with one draw call, a custom shader is used.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
VARYING vec4 color;
float rectangle(vec2 samplePosition, vec2 halfSize) {
vec2 componentWiseEdgeDistance = abs(samplePosition) - halfSize;
float outsideDistance = length(max(componentWiseEdgeDistance, 0.0));
float insideDistance = min(max(componentWiseEdgeDistance.x, componentWiseEdgeDistance.y), 0.0);
return outsideDistance + insideDistance;
}
void MAIN() {
vec2 tc = UV0;
vec2 uv = fract(tc * UV1.x); //UV1.x number of levels
uv = uv * 2.0 - 1.0;
uv.x = 0.0;
uv.y = smoothstep(0.0, 0.2, rectangle( vec2(uv.x, uv.y + 0.5), vec2(0.2)) );
BASE_COLOR = vec4(color.xyz * mix( clamp( ( vec3( 0.4, 0.4, 0.4 ) + tc.y)
* ( vec3( 0.6, 0.6, 0.6 ) + uv.y)
, 0.0, 1.0), vec3(1.0), UV1.y ), 1.0); // UV1.y as is roofTop
ROUGHNESS = 0.3;
METALNESS = 0.0;
FRESNEL_POWER = 1.0;
}
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