Textured triangle surface changes shades based on camera angle despite lighting set to false

[owenlamont]

I was rendering a textured triangle surface using the following code:

import ipyvolume as ipv
import numpy as np
from PIL import Image

background = Image.open("Carnarvon.png")
fig = ipv.figure(lighting=False)
x = np.array([0,  1.0,  1.0,  0])
z = np.array([0,  0, 1.0, 1.0])
y = np.array([0., 0, 0., 0])
u = np.array([0,  1.,  1.,  0])
v = np.array([0,  0, -1., -1.])
triangles = [(0, 1, 2), (0, 2, 3)]
m = ipv.plot_trisurf(x, y, z, triangles=triangles, u=u, v=v, texture=background)
ipv.show()

The triangle surface gets closer to the original image colour the more perpendicular the camera is to the surface, and blacker the more the camera is parallel to the surface - but I expected the colour of the triangle surface to stay consistent, and true to the original image colors, regardless of the camera angle. See below:

I'm used the Anaconda installs on MacOS with the following versions:

• ipyvolume 0.5.1
• pythreejs 2.0.2
• Python 3.7.1