gistfile1.coffee

xmin = 0
xmax = 0
zmin = 0
zmax = 0
for vertex, i in exports.face.vertices
    switch i % 3
        when 0
            xmin = Math.min xmin, vertex
            xmax = Math.max xmax, vertex
        when 2
            zmin = Math.min zmin, vertex
            zmax = Math.max zmax, vertex

xnmax = xmax + Math.abs xmin
znmax = zmax + Math.abs zmin

for vertex, i in exports.face.vertices
    switch i % 3
        when 0
            exports.face.vertices[i] = ((vertex + Math.abs(xmin))/xnmax)*2 - 1
        when 1
            exports.face.vertices[i] = 0
        when 2
            exports.face.vertices[i] = ((vertex + Math.abs(zmin))/znmax)*2 - 1