c++ - osg/osgEarth 中的 gluPartialDisk
问题描述
我一直在尝试在 osgEarth 中创建一个类似 openGL gluDisk 的对象。到目前为止,我已尝试执行以下操作(已编辑,这是正确答案):
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);
}
最初让我难过的是我没有太多的图形知识。在某处我读到,在绘制轮廓时,请按顺时针方向进行。当以逆时针方向绘制轮廓时,当与顺时针绘制的点结合时,它们将“切掉”或创建一个“孔”。在测试该方法时,我最初是在顺时针方向用较小的圆点填充“孔”轮廓,这就是它不起作用的原因。
解决方案
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);
}
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