c++openglopenscenegraphosgearth

gluPartialDisk in osg/osgEarth


I've been trying to create an openGL gluDisk like object in osgEarth. So far I've attempted to do the following (Edited, this is the correct answer):

void ViewDriver::drawCircZone(double lat, double lon, double innerRadius, double outerRadius, QColor color, double beginAngle, double endAngle){
    GeometryFactory g;
    osg::ref_ptr<osgEarth::Geometry> outerCircleGeom = g.createArc(osg::Vec3d(lat, lon, 0), convertFromMetersToMercDeg(outerRadius), beginAngle, endAngle);
    osg::ref_ptr<osgEarth::Geometry> innerCircleGeom = g.createArc(osg::Vec3d(lat, lon, 0), convertFromMetersToMercDeg(innerRadius), beginAngle, endAngle);

    osg::Vec3dArray* outerCircArray = outerCircleGeom->createVec3dArray();
    osg::Vec3dArray* innerCircArray = innerCircleGeom->createVec3dArray();

    Vec3dVector* diskVec = new Vec3dVector;

    for(int i = 0; i < outerCircArray->size() - 1; i++){
        diskVec->push_back((*outerCircArray)[i]);
    }
    //This is important for closing the shape and not giving it a Pac-Man-like mouth
    diskVec->push_back((*outerCircArray)[0]);

    //This is how you make a "hole", by iterating backwards 
    for(int i = innerCircArray->size() - 1; i >= 0; i--){
        diskVec->push_back((*innerCircArray)[i]);
    }

    osg::ref_ptr<osgEarth::Symbology::Ring> diskRing = new Ring(diskVec);
    diskRing->close();

    osg::ref_ptr<Feature> circFeature = new Feature(diskRing, view->getMapViewer()->geoSRS);

    Style circStyle;
    circStyle.getOrCreate<PolygonSymbol>()->outline() = true;
    circStyle.getOrCreate<PolygonSymbol>()->fill()->color() = Color(color.red()/255.0, color.green()/255.0, color.blue()/255.0, 1.0);
    circStyle.getOrCreate<AltitudeSymbol>()->clamping() = AltitudeSymbol::CLAMP_RELATIVE_TO_TERRAIN;
    circStyle.getOrCreate<AltitudeSymbol>()->technique() = AltitudeSymbol::TECHNIQUE_DRAPE;

    osg::ref_ptr<FeatureNode> circNode = new FeatureNode(circFeature, circStyle);
    circNode->setDynamic(true);

    view->getMapNode()->addChild(circNode);
}

What stumped me originally was that I don't have a lot of graphics knowledge. Somewhere I read that when drawing outlines, do it in clockwise direction. When drawing outlines in counter clockwise direction they will "cut-out" or create a "hole" when combined with clockwise-drawn points. I was filling the "hole" outline with the smaller circle's point in a clockwise direction originally when testing that method which was why it didn't work.


Solution

  • void ViewDriver::drawCircZone(double lat, double lon, double innerRadius, double outerRadius, QColor color, double beginAngle, double endAngle){
            GeometryFactory g;
            osg::ref_ptr<osgEarth::Geometry> outerCircleGeom = g.createArc(osg::Vec3d(lat, lon, 0), convertFromMetersToMercDeg(outerRadius), beginAngle, endAngle);
            osg::ref_ptr<osgEarth::Geometry> innerCircleGeom = g.createArc(osg::Vec3d(lat, lon, 0), convertFromMetersToMercDeg(innerRadius), beginAngle, endAngle);
    
            osg::Vec3dArray* outerCircArray = outerCircleGeom->createVec3dArray();
            osg::Vec3dArray* innerCircArray = innerCircleGeom->createVec3dArray();
    
            Vec3dVector* diskVec = new Vec3dVector;
    
            for(int i = 0; i < outerCircArray->size() - 1; i++){
                diskVec->push_back((*outerCircArray)[i]);
            }
            //This is important for closing the shape and not giving it a Pac-Man-like mouth
            diskVec->push_back((*outerCircArray)[0]);
    
            for(int i = innerCircArray->size() - 1; i >= 0; i--){
                diskVec->push_back((*innerCircArray)[i]);
            }
    
            osg::ref_ptr<osgEarth::Symbology::Ring> diskRing = new Ring(diskVec);
            diskRing->close();
    
            osg::ref_ptr<Feature> circFeature = new Feature(diskRing, view->getMapViewer()->geoSRS);
    
            Style circStyle;
            circStyle.getOrCreate<PolygonSymbol>()->outline() = true;
            circStyle.getOrCreate<PolygonSymbol>()->fill()->color() = Color(color.red()/255.0, color.green()/255.0, color.blue()/255.0, 1.0);
            circStyle.getOrCreate<AltitudeSymbol>()->clamping() = AltitudeSymbol::CLAMP_RELATIVE_TO_TERRAIN;
            circStyle.getOrCreate<AltitudeSymbol>()->technique() = AltitudeSymbol::TECHNIQUE_DRAPE;
    
            osg::ref_ptr<FeatureNode> circNode = new FeatureNode(circFeature, circStyle);
            circNode->setDynamic(true);
    
            view->getMapNode()->addChild(circNode);
    }