Usually you can start from real world terrain data, which covers the Heightmap / Satmap and you have to recreate the Mask. Update satmap / mask with forests and roads (you can export satmap / roads to an image the size of your satmap and apply in photoshop).Create forests & roads using Terrain Builder shapes (forests can be usually be derived from your satmap, if you painted forests in there).Setup initial config.cpp for your map (addon).Setup grass and landscape layers (layers.cfg).The process of creating a terrain can be split to stages: You need to read the Atlas terrain building guide.
