def buildEdgeDict(faces):
	"""
	Arguments:
		faces ([[vIdx, ...], ...]): A face representation

	Returns:
		{vIdx: [vIdx, ...]}: A dictionary keyed from a vert index whose
			values are adjacent edges
	"""
	edgeDict = {}
	for face in faces:
		for f in range(len(face)):
			ff = edgeDict.setdefault(face[f-1], set())
			ff.add(face[f])
			ff.add(face[f-2])
	return edgeDict