FME supports translation of 3D geometry from one format to another, provided that each format itself supports 3D. The extent of 3D support is limited by the level of each format’s own 3D support. If one format supports solids and another supports only faces, the solids may be converted to faces during the translation. Because of this, each combination of reader and writer will have its own unique characteristics and should be tested. It is also important not to assume a particular transformer will support 3D until you have verified it first.
As with other enhancements to FME, the first step is the extension of core infrastructure and new geometry model, in this case to handle 3D constructs. Over time, this enhanced 3D support will be implemented throughout FME transformers and formats where this provides the most value.