Manufacturing guy-at-large.

T-Spline modeling

Added on by Spencer Wright.

This model took me about 45 minutes. It's basically the first "organic" model I've ever created. 100% T-spline geometry, all on a piece of free software. 

I started with a single torus on the XY plane for one of the eyepieces. I applied a "Mirror-Duplicate" on the YZ plane, creating a second eyepiece that automatically mirrors whatever I did on the first. Then I created the only sketch in the entire model - a basic nose bridge, spanning from eyepiece to eyepiece. I created a "Bridge" feature between the two eyepieces, then began to sculpt. A bit into the process, I created the temples by extruding them from the faces closest to the top corners of the eyepieces.

At this point, I could export STLs and have this printed as a full scale, physical, part-in-hand mockup. The entire process - from sketching the torus to completing the print - would take about 4.5 hours. 

Note: I'm assuming you're using FDM (a process I'll begrudgingly accept for quick mockup purposes), e.g. MakerBot, and that your Lean, One-Piece-Flow Supply chain (as it were) is ready and running smoothly.