I made some changes in the Blender's Wevefront obj export script to fix some issues and add some maps in the mtl file. I made this quickly to satisfy my needs, feel free to change it or to suggest changes, however I won't do much on that, so anybody could change it. It works with Blender 2.49.
- . Peviously the diffuse map assigned to the UV layout in the image editor was exported (map_kd entry), now it's the image assigned via the col mapping.
. Bump map is exported via map_bump entry in the mtl
. Alpha map is exported via map_d entry in the mtl (assigned as opacity map in Octane)
. Some minor changes, I took some liberty in the interpretation of the other values based on my needs, hope they also meet yours.
Enrico