Follow up on a few of these. Let me start with a basic work flow for learning
Focus on getting a map rigged and setup. Dont worry about textures and art. Just get it into the game and able to run around in it.
The level builder pdf can be pretty confusing but it has the answers for most of it.
Trial and error through it. Its the best way to learn but not the easiest. Follow along with other tutorials already here on gr.net
Maps break down into a few things. Room groups, sherman levels, and portals. Once you understand these you have the foundation you need to continue.
Focus on creating command maps after.
Then focus on lighting. Scripting etc...
Last but not least. Windows,water, glass, doors, trees, destructible items, these all require a little individual rigging or prep.
Skyboxes are fairly simple as well but ill get into that later.
Textures are rsb just like any other game model. Less is more. So utilizing atlasses for many objects is important. The terrain can be two maps mixed. A basic color map mixed with a detail texture map. It works and looks ok.
The polygon limitations are pretty simple. GR does not handle high density mesh well due to its lighting system.
Create your level in the same style as GR and thats about as good as it gets. Unfortunitly you cant fake it to make it better.
So things like accurate prebaked lighting, huge texture atlases they dont really improve quality much. I tested it. It works on really small levels but nothing big.
You can create modular levels and assets. Its best to weld it all at the end to prevent collision issues.
Also do utilize lots and lots of hidden colliders. Geomtery thats more complicated will not offer good collision at all.
Take it step by step and before you know it you will have a map finished.
Tutorials for trees and vegitation are on gr.net as well.
Use 3dsm 5 for building the level. You can use other versions for creating mesh but the bulk of work is done in 5.
This should be confusing sounding and it will be lol. Let me know if you need me to talk about anything.