[Visualpython-users] materials.texture(mapping=????)

Hello my great friends!
I've been trying vpython today and my project target is to display a
series of image into faces... one image for each face, but now it's
not really the problem.

My problem is at the:

materials.texture(mapping='mode')

which I dont have any clue what value to fill in the 'mode' to pass
into the mapping argument, is there any decent resources/reference for
vpython that I can use?
Because after awhile searching the original website I can't find any
"API reference" or something like that.

In case you people want to see my code, here it is:

from visual import *

#using P.I.L (Python Imaging Library)
import Image

#create frame object
f = frame()

#create a red face
model = faces(frame = f)
model.append(pos = (-3,0,-3))
model.append(pos = (-3,0,3))
model.append(pos = (3,0,3))
model.append(pos = (-3,0,-3))
model.append(pos = (3,0,-3))
model.append(pos = (3,0,3))
model.make_normals()
model.make_twosided()

#get material from file
name = 'wgauss'
width = 1840
height = 321
im = Image.open('w-gauss_of_v1.1_0.50_04.png')
materials.saveTGA(name, im)
data = materials.loadTGA(name)

#set model's material
model.material = materials.texture(data=im, mapping='sign')

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Thanks in advance for any (helpful) reply