Hiding transitions with decoratives

With Alien Biomes V3, I'm trying to keep the number of tilesets to a minimum. As a result, there are lots of situations where the colour difference between two touching tilesets is much greater than intended. This creates abrupt terrain changes, or visible banding on the terrain, where ideally there would be a much smoother gradient.

This image is an experiment where the raw tileset terrain (shrunk down in the bottom left) has the transitions disguised with decoratives. A decorative in Factorio is a visual-only graphic added to the terrain, like grass, small rocks, and mud patches. Larger things like trees, big rocks, and cliffs are not decoratives but are entities instead (even if they do decorate the terrain). Decals are a specific type of decorative that is drawn in to the terrain layer instead of above it. Examples are mud patches and biter fungus. This means that decals (usually) go under things like concrete, where as grass and shrubs could draw over concrete (if they weren't removed by the concrete placement).

Most of the heavy lifting in this experiment is done with mud and stone decals that are tinted specifically for each tileset. This lets them partially overlap neighbouring tilesets to disguise the transition. This alone does a reasonable job at hiding the transitions but it does make things look quite patchy. The other elements like cliffs, rocks, trees, & shrubs help disguise a lot of the patchiness by giving the eye other things to focus on.

Doing these sorts of tests is important for me to know how how many tilesets I need to cover the gaps between the more extreme terrain styles. The more I can do with decoratives the less I need to do with "filler" tilesets, which means terrain generation can be faster, the mod download can be smaller, and the mod consumes less of the 255 tilset slots. Decoratives are easier to make look good when tinted so they don't need unique graphics. Tinted tilsets are possible but they tend to look much worse as the colour range gets crushed, plus even if they don't have unique graphics they still take up one of the tilset slots.

Overall I think it is working quite well. You can still see the terrain banding if you look for it, but where the raw tiles in the bottom left look artificial and wrong, with the decoratives it looks quite natural.