How to get the height of a building?

[luohuiiqng]

Hello!
With the osgearth_city example, I learned how to load a 3D building on Earth. But if I want to get the height of a certain building, how do I do it? Thank you very much!

[gwaldron]

If a building feature has a height defined, it will likely be in a Feature attribute. You can use the Feature API to get it.

Feature* feature;
...
auto height = feature->getDouble("height");

The attribute containing the height, and the units, and whether there is a height defined at all ... these things all depend on the dataset.

[luohuiiqng]

Thank you!
If the code to load the building is as follows, what should I do:

void addBuildings(osgEarth::Map* map){
    //data
    osgEarth::OGRFeatureSource* data = new osgEarth::OGRFeatureSource();
    data->setName("buildings-data");

    //E:/Compiler/osgearth/data/boston_buildings_utm19.shp
    data->setURL("E:/Compiler/osgearth/data/boston_buildings_utm19.shp");

    osgEarth::Style buildingsStyle;
    buildingsStyle.setName("default");

    osgEarth::ExtrusionSymbol* extrusion = buildingsStyle.getOrCreate<osgEarth::ExtrusionSymbol>();
    extrusion->heightExpression() = osgEarth::NumericExpression( "3.5 * max( [story_ht_], 1 )" );
    extrusion->flatten() = true;
    extrusion->wallStyleName() = "building-wall";
    extrusion->roofStyleName() = "building-roof";

 
    osgEarth::PolygonSymbol* poly = buildingsStyle.getOrCreate<osgEarth::PolygonSymbol>();
    poly->fill()->color() = osgEarth::Color::White;


    osgEarth::AltitudeSymbol* alt = buildingsStyle.getOrCreate<osgEarth::AltitudeSymbol>();
    alt->clamping() = alt->CLAMP_TO_TERRAIN;
    alt->binding() = alt->BINDING_VERTEX;

    osgEarth::Style wallStyle;
    wallStyle.setName("building-wall");
    osgEarth::SkinSymbol* wallSkin = wallStyle.getOrCreate<osgEarth::SkinSymbol>();
    wallSkin->library() = "us_resources";
    wallSkin->addTag("building");
    wallSkin->randomSeed() = 1;

   
    osgEarth::Style roofStyle;
    roofStyle.setName("building-roof");
    osgEarth::SkinSymbol* roofSkin = roofStyle.getOrCreate<osgEarth::SkinSymbol>();
    roofSkin->library() = "us_resources";
    roofSkin->addTag("rooftop");
    roofSkin->randomSeed() = 1;
    roofSkin->isTiled() = true;

   

    //combine
    osgEarth::StyleSheet* styleSheet = new osgEarth::StyleSheet();
    styleSheet->addStyle(buildingsStyle);
    styleSheet->addStyle(wallStyle);
    styleSheet->addStyle(roofStyle);    


    osgEarth::ResourceLibrary* reslib = new osgEarth::ResourceLibrary("us_resources", "E:/Compiler/osgearth/data/resources/textures_us/catalog.xml");
    styleSheet->addResourceLibrary(reslib);

    osgEarth::FeatureDisplayLayout layout;
    layout.tileSize() = 500;

    osgEarth::FeatureModelLayer* layer = new osgEarth::FeatureModelLayer();
    layer->setName("Buildings");
    layer->setFeatureSource(data);
    layer->setStyleSheet(styleSheet);
    layer->setLayout(layout);
    layer->setMaxVisibleRange(90000.0);

    map->addLayer(layer);
}

[gwaldron]

In this case, the height is in the story_ht_ attribute, as you can see in the heightExpression.

osg::ref_ptr<FeatureCursor> cursor = data->createFeatureCursor();
while(cursor->hasMore()) {
    Feature* feature = cursor->nextFeature();
    auto height_in_stories = feature->getDouble("story_ht_");
}

[luohuiiqng]

Thank you very much!