3D content refers to a digital object with 3D geometry. 2D representations (images) of three-dimensional real-world objects (e.g. sculptures) should not be given the type 3D in Europeana records.
The quality of 3D content depends on a number of factors, including but not limited to the number of points and vertices, the underlying research and production methods, and the choices made in processing the data. For users the quality of their experience of 3D also depends on high speed connectivity, load times and their set up. The ability to reuse 3D content depends on the availability of metadata that describes how the content has been created.
If you are contributing 3D material because you want it to be discoverable via the Europeana website then you need to provide, as a minimum, either a link to the 3D content (via a viewer or a link to a direct object) or a link to a website in which the file can be viewed online (both in the edm:isShownBy property). Note that embedding 3D content into PDF documents is not a recommended format for new content.
You may also provide a link to a 2D image file large enough to create a preview image (in the edm:object property) to illustrate search results on the Europeana collections website, for example a scene within a model which could be offered as a preview.