For the Environment Module at college I wanted to practice foliage and terrain, and also focus on lighting within Unreal Engine 4. I was impressed by the real time depth of field and post effects, and used that to limit the player within a seemingly open environment.
It was also the first time using Substance designer, and I ended up using it with pretty much all my texturing work for this environment.
I also enjoyed building the foliage shaders with subsurface scattering and faking wind through vertex colour animation.
Vertex colour ended up blowing my mind and used it on my terrain to blend between different materials.