Put existing map-model from other game to Garry's Mod

Hello! I’ve made an exporter of Scenery from one PS2 game into Obj file and now i want to export it into GM.
As i searched, there is no way of importing Obj to hammer. The only advice i found - remodel map in the Hammer Editor.
If i could remodel that maps, i wouldn’t make exporter, so, remodeling is not an option. Is there any other ways?
Thank you for your help!

You can import .obj to modelling software such as Blender or 3ds Max and export them to .smd which can be compiled into a Source engine .mdl to be used in maps

I personally recommend Blender and Blender Source Tools to export to .smd and compile into .mdl. Here’s a quick guide I found on Valve’s developer wiki aswell showing the exporting process

Thank you for your reply. Sadly, i cannot complie that smd into mdl, cuz maximum of used materials is 32 and map has 113. Or do i have to separate map into small entities, export them all into smd->mdl and then place them all as static objects in map?

break up the map. in 3DS max you can select by material. I’d imagine blender has the same ability.

This.
I also wouldn’t have the entire map in the form of static models as lighting will look horrible. I’d reconstruct the large parts of the map (walls, floor, ceiling etc) in the form of brushes, and have details (doors, lights, fences, etc) filled in by models or whatever