Exported Maya Model Missing Faces in THREE.js

Question

I have some very basic models I've exported as obj and converted using the included convert_obj_three.py script. Most of the models have been fine but some seem to have missing faces.

I'm using Maya for my models and ensuring that I've centered my object accordingly, frozen all transformations to "zero-out" the transform data in addition to deleting all history of the object before exporting the obj. I'm going to be rebuilding a few things and see if there's anything that stands out as to why this is happening, but wanted to ask if anyone knows of a specific issue that may be occurring here. Example plunker here: http://plnkr.co/edit/6mEkbm83FEBdygfBVjXh?p=preview

Answer 1

Could've sworn I checked these before but, it turns out my normals were inverted for some of the faces. Obviously, fixing that in Maya resolves the issue. :D