To make realistic Simcity 4 terrain, like the one in Simcity 4 Europa Terrain, I used this process:
- Create a multiple layered Photoshop or Paint Shop Pro file as described in this article, which is used to seperate the difference between land and water.
- Use a big solid brush tool, at land layer (about light=84) to create the basic filled land outlines. Blur this land outline to soften the land.
- Use a huge, soft brush tool on a mostly transparent layer to add some basic hills in the land (and the ocean).
- Create another layer. Use a semi-opaque solid brush tool, at the top land layer (light=255), to create the outlines of mountain ranges. By using semi-opaque, it will draw below 255, and ranges can accumulate on top of each other to increase in height.
- Blur these lines to soften the mountains up.
- Use Paint Shop Pro's retouch tool, using it on Smudge, very softly (0% hardness) and very gritty (40-70% density). Use this smudge to create the semi-mountains between land and mountain ranges. With some practice you can get the land looking fairly realistic (as seen in Simcity 4 Europa Terrain).
- As this is on another layer, you can reduce the opacity of the layer to reduce the effects of the mountains.
- To make it easier, create multiple mountain ranges per file, so it's easier to revert changes and adjust the effects of each layer.
- You can use another huge, soft brush tool to add additional hill/valley effects in the image.