Hi,
I have some information about why some mtl files don't load. Basically it comes down to the fact they have spaces in the names. The OBJ spec doesn't support this. You can use more than one mtl file in a model and spaces are used to separate the filenames on the mtllib line. This means a line in the file which looks like:
mtllib cruise ship.mtl
is strictly speaking referring to two files - one file called "cruise" and another file called "ship.mtl". So basically that's the problem.
It's easy enough to fix yourself. Rename the mtl file so there are no spaces in the name ( i.e. cruise_ship.mtl ). Next open the obj file in a text editor and look for the line which starts with mtllib. It will probably be near the top of the file, but search for it otherwise. Change the mtllib line to refer to the renamed mtl file:
mtllib cruise_ship.mtl
Now everything should work as expected.
There are obviously a lot of obj files which do use spaces in the name of the mtl file. I came across one myself when I was looking for models to test the new texture system with. I'll look into improving the handling of this in TG2's OBJ importer.
Regards,
Jo