@zep tline3d documentation is incorrect!
doc:
tline3d(src, x0, y0, x1, y1, u0, v0, u1, v1, [w0, w1])

code (works):
tline3d(src, x0, y0, x1, y1, u0, u1, v0, v1, [w0, w1])

this is inconsistent with x/y parameters ordering!