That teaches you how to apply textures to a curved surface.
Also consider adding in other features, such as rollings hills, forest areas, underground cave complexes, a subway system for black-ice, also instead of just a wall around the outside of the map, consider a 3D skybox to make it look like the map goes on forever. Once again there’s a tutorial for a 3D skybox on interlopers: http://www.interlopers.net/tutorials/1839
Also, if you want to learn about more advanced map elements consider reading and watching tutorials.
A few facepunch users such as myself have their own YouTube channels with tutorials on them:
There are a few other channels which I cannot remember, also I advise you not to watch a certain users tutorials, he goes by the alias of 3KliksPhillip.
Thanks for the ideas but i got problems getting css and gmod models together so i can add some trees from gmod, i currently only edit in css engine, if you could point me in a direction on how i can do that i would love to add a forest
When you download the models for your Garrys Mod game, whether they be trees or whatever instead of placing them inside your addons folder, browse into the folder which you downloaded, you should then see a models and materials folder (Usually) copy these two folders into the counter strike source game directory, it will ask you if you want to overwrite the folders, just say Yes.