I have some OBJ which imported correctly in 3.3.1 and doesn't work on 4. doesntWork.obj does not expose the texture correctly, while works.OBJ does.
The only difference is where the g (group) and usemtl are placed. Tinkering with the OBJ file, I think that the "group" must be defined after the "mtllib". If not, the problem happens.
I don't know if this is a malformed OBJ file either. The OBJ format is ... well... very badly defined. Both OBJ files correctly load on 3DSMax 2013 though.
I have some OBJ which imported correctly in 3.3.1 and doesn't work on 4. doesntWork.obj does not expose the texture correctly, while works.OBJ does.
The only difference is where the g (group) and usemtl are placed. Tinkering with the OBJ file, I think that the "group" must be defined after the "mtllib". If not, the problem happens.
I don't know if this is a malformed OBJ file either. The OBJ format is ... well... very badly defined. Both OBJ files correctly load on 3DSMax 2013 though.
objs (renamed) doesntWork.txt works.txt
material (renamed... but any material and texture file will do, the problem seems to be in the OBJ) floorTest.txt