I decided to use the terrain editor in UDK for the base of my level. I created a large plane and started using the brushes to create the terrain I wanted. I found that the brushes were intuitive and I had a lot of fun shaping the landscape. I did have some worries about how to block in the player though. I didnt want to have perfectly straight up mountains perfectly enclosing the area. And one thing that always bugged me in games was invisible barriers! I hated the feeling of being trapped unfairly when I can see more land and things to look at in the distance. I think invisible collision walls are definitely a big way of damaging the player's immersion in the game.
So I tried to make the mountains seem more natural and created varying depths and made some encroach on the area.
I made some tweaks to them, going back and forth between photoshop. Eventually I realised that once all the trees and plants and rocks are in the level, it would greatly decrease your line of sight. When I played on the level, the ground in front of me looked perfectly fine, and since jungles are so dense, you wouldn't be able to see the tiling on the ground or even the mountains.
I'm keeping with the bluey/green theme in my level, so there's patches of blue moss on the ground throughout.
I'm adding more detail to the terrain now, added the ramp formation that leads to a ledge, and also a deep area for the pool and waterfall that will go in the top right, and another depression for a smaller pond. Also painted the terrain textures to correspond with this geometry.
I did encounter one problem when I suddenly got really harsh shadows on certain parts of the level mesh. After some searching as well as checking the settings in the single dominant directional light, I found that I had accidentally duplicated the terrain. This is easily done when painting terrain, textures and panning your view since you're having to hit so many keys.