Core Theme: Procedural generation as much as possible, removing months of extra work.
Terrain Edit: Novigrad, one of 3 main areas
Generated with World Machine
46x46 tiles, 512x512 each (23552^2), 63MB
0.37cm between vertices, ~74 km^2
Custom vegetation generator
16 people working on Engine.
Automatic occlusion culling + streaming with Umbra.
Terrain and vegetation: http://twvideo01.ubm-us.net/o1/vault/GDC2014/Presentations/Gollent_Marcin_Landscape_Creation_and.pdf
Simplogon LOD generator: http://twvideo01.ubm-us.net/o1/vault/GDC2014/Presentations/Balazs_Torok_Speed_Up_Your.pdf
Umbra 3 culling + Streaming: http://twvideo01.ubm-us.net/o1/vault/GDC2014/Presentations/Bushnaief_Jasin_Solving_Visibility_In.pdf
Correct me if wrong, tessellate if old.