Geoselection at py level inconvenient

• Means must keep regenerating GLTF... as change selection.

Moving to GScene::createVolumeTree_r would allow reuse of OpticksQuery

375 GSolid* GScene::createVolumeTree_r(nd* n, GSolid* parent)

806 void AssimpGGeo::convertStructure(GGeo* gg, AssimpNode* node, unsigned int depth, GSolid* parent)
807 {
808     // recursive traversal of the AssimpNode tree
809     // note that full tree is traversed even when a partial selection is applied
810
811
812     GSolid* solid = convertStructureVisit( gg, node, depth, parent);
813
814     bool selected = m_selection && m_selection->contains(node) ;
815
816     solid->setSelected(selected);
817