Changing Scale Results in Shading Effect

[micheus]

Telsavision, the .mtl file was absent, so what I could to do was to:
- Import the 3x3tech.obj into Wings3D;
- Import Image j2B6Jyv.jpg;
- Assign the image to the diffuse texture of the Material in Outline window;

Everything was fine in Wings3D.
Then, I used File->Export->Wavefront (*.obj) - all default settings - and I got an .obj file as well as a .mtl in which I could to confirm Wings3D is referencing the .jpg image - no new image was created by Wings3D:

# Exported from Wings 3D 2.0.2
newmtl Material
Ns 100.0
d 1.0
illum 2
Kd 1.0 1.0 1.0
Ka 1.0 1.0 1.0
Ks 1.0 1.0 1.0
Ke 0.0 0.0 0.0
map_Kd j2B6Jyv.jpg

So, I think the problem would be related to the other informations like normals, groups,...
By comparing the original and exported .obj I noticed the best settings to make both be similar is using these settings (mainly the checkbox controls):


But, even with 'Export normals/smoothing groups' unchecked I noticed Wings3D seems to be exporting information related to that:

...
vt 0.99847300 0.74889200
g geo_ground_Cube
usemtl Material
s 1
f 1/6/ 10/7/ 41/1/ 2/4/
...

That "s 1" means "smooth group 1", but as none vertex normal information is exported it should be ignored by application reading it (I think ).
In case you had used that settings when exporting, maybe the software isn't take this in account.

In the original .obj file (generated by Blend) I noticed it doesn't include the group information and the smooth group was explicitly set OFF:

...
vt 0.668974 0.212371
usemtl Material
s off
f 14/1 13/2 11/3 12/4
...

Concluding, if you didn't use the settings as I shown in the image, please try that and see the result.
If the result remains the same, please open your exported .obj in a editor like Wordpad (Windows) and look for the line with the "g" information and remove it and in the line with the "s" information change it from "1" to "off" (the double quotes should not be included). Then, save the file and check the result again.

Please give me a feedback.
Thanks