Todo: Update the neck-removing processing pipeline from original BFM model.

The original version with neck:

The refined version without neck:

These two images are rendered by MeshLab.

bfm_show.m shows how to render it with 68 keypoints in Matlab.

Attention: the z-axis value of bfm.ply and bfm_refine.ply file are opposed in model_refine.mat, do not use these two ply file in training.