Here is the obj file that is loaded properly with Maya but not Irrlicht:
# XSI Wavefront OBJ Export v3.0
# File Created: Tue Jul 06 14:16:28 2004
# XSI Version: 3.0.2002.1025
g grid
#begin 16 vertices
v -4.000000 0.000000 -3.000000
v -2.831858 0.000000 4.000000
v 4.000000 0.000000 -3.000000
v 2.831858 0.000000 4.000000
v 2.000000 0.000000 0.000000
#5
v -2.000000 0.000000 0.000000
v -6.000000 0.000000 0.500000
v 6.000000 0.000000 0.500000
v -2.831858 5.000000 4.000000
v 2.831858 5.000000 4.000000
#10
v 6.000000 5.000000 0.500000
v 4.000000 5.000000 -3.000000
v 2.000000 5.000000 0.000000
v -2.000000 5.000000 0.000000
v -4.000000 5.000000 -3.000000
#15
v -6.000000 5.000000 0.500000
#end 16 vertices
#begin 16 normals
vn -0.034421 0.000000 -0.999407
vn -0.405534 0.000000 0.914080
vn 0.034421 0.000000 -0.999407
vn 0.405534 0.000000 0.914080
vn -0.471858 0.000000 -0.881675
vn 0.471858 0.000000 -0.881675
vn -0.994145 0.000000 0.108051
vn 0.994145 0.000000 0.108051
vn -0.362720 0.447214 0.817578
vn 0.362720 0.447214 0.817578
vn 0.845825 0.525480 0.091931
vn 0.024942 0.689152 -0.724188
vn -0.422043 0.447214 -0.788594
vn 0.422043 0.447214 -0.788594
vn -0.024942 0.689152 -0.724188
vn -0.845825 0.525480 0.091931
#end 16 vertex normals
#begin 9 faces
f 9//9 10//10 11//11 12//12 13//13 14//14 15//15 16//16
f 2//2 9//9 16//16 7//7
f 4//4 10//10 9//9 2//2
f 8//8 11//11 10//10 4//4
f 3//3 12//12 11//11 8//8
f 5//5 13//13 12//12 3//3
f 6//6 14//14 13//13 5//5
f 1//1 15//15 14//14 6//6
f 7//7 16//16 15//15 1//1
#end 9 faces
There is an incorrect triangle created by connecting vertex 10, 15, 16(8 vertices, from 9 to 16).
If you fire up the MeshViewer from example 9, load this obj, and you will see what I mean when you scale it to 5.0, 5.0, 5.0 and rotate it.
Andy