HaloMods "Classic" Read-only Archive

I've been working on a project based off Coagulation.

I need some help with a model. I was wondering if there was a way to edit the actual terrain and shape of the base map. I would like to edit the map to have some walls. If I can't edit the actual map I would just like to inject the walls and place them. I'm horrid with model making, injection, placing and collision. Any help would be appreciated.

There is an app called bsp master which is supposed to let you edit the bsp (including collision) but it doesn't work quite that well. Seems it leaves holes in the collision and stuff.
You'll probably want to go the mach/scen injecting route.