With the release of ArcGIS 10.3.1, it is now possible to publish 3D layers to on-premised Portal/Server and combine them up with existing Portal or ArcGIS Online 2D feature layers. This paper will look at the system and configuration requirements for the publication of these layers and the integration and curation of these and other services that make up rich 3D web scenes. This paper also looks at the process for the publication of high resolution Local Elevation services on ArcGIS Server and how they are shared with ArcGIS Online and ArcGIS Pro.
http://www.esri.com/~/media/Files/Pdfs/library/whitepapers/pdfs/publishing-hosted-3d-feature-layers....