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.
