Save volume rendering as STL file

[lassoan (Andras Lasso)]

Note that augmented or virtual reality does not require STL. Slicer can already render beautiful volume rendered scenes without segmentation in virtual reality headsets, in color, in real-time, even in 4D, on any OpenVR-compatible headset (HTC Vive, any Windows mixed reality headsets, Oculus Rift, etc.), by a single click. Virtual reality provides solutions for many use cases that previously was only possible to address by 3D printing. Of course, for some cases 3D printing is still needed and the volumetric printing is a really nice option.