Florentina -- Realistic Topography

[Peter Toth]

Hello Guild,

Again experimenting with poor man's software (GIMP and Wilbur) to create some topography that looks believable. I realize the drainage pattern problem at the top center; for some reason, Wilbur directed a drainage basin upward after I had cropped the original image. I've neglected it for now, concentrating primarily on refining the topography until it satisfies my standards.

Again, thank you for visiting.

Florentina3.png

Peter

[QED42]

Looking very good!

[Diamond]

I really like this! Wish I could figure out how to run Wilbur, cause this is exactly a style I'd like to experiment with.

[delguidance]

So I go in and manually dig out a channel so the drainage will definitely run down to the river. It doesn't look so good in Wilbur, but I fix it when I go from Wilbur to Gimp.

One thing I find missing are mesas, areas with lots of cliffs, or uplands in general. Those are absent when you work with Wilbur, so don't forget to decide if you want them and add them in on your own.

[waldronate]

for some reason, Wilbur directed a drainage basin upward after I had cropped the original image.

Wilbur follows the gradient and treats the edges of images as though they are flat. If you want to keep the edge connectivity, you'll need to paint a line at higher altitude across the problematic valleys manually and keep forcing things back to your desired state. It's ugly. Oftentimes, it's simpler to work with an image of a larger area as long as you can and making sure to keep important river basins on the map if at all possible.
The map here looks quite plausible. The coloring is fairly straightforward and understandable.

One thing I find missing are mesas, areas with lots of cliffs, or uplands in general. Those are absent when you work with Wilbur, so don't forget to decide if you want them and add them in on your own.

A major failing (one of many) with the erosion process in Wilbur is that it's the same everywhere. That doesn't happen much in the real world except in big piles of dirt or really soft rocks like certain sandstones. Most places have hard stuff under the soft stuff that Wilbur "models" and that hard stuff significantly affects how things end up looking. Another major problem is that the data is represented by a raster image of altitudes, meaning that there is never an overhang anywhere to allow for things like cliff collapse and general mass wasting processes. The rectangular grid nature of the underlying data also appears in "water flow" because the system computes a maximum of 8 directions for flow.
If you want cliffs, the simplest way to keep them is to do what the real world does: keep uplifting as you erode. Keep a selection mask of where you want your cliff to be, load the mask, add some amount of altitude after every time you erode, then deselect before doing more stuff. This technique will continuously reinforce the break that the erosion tries to blur out. The hard part is being aggressive enough to keep the cliffs while not being so aggressive that they overwhelm everything. If you want something like a rift valley, you can use a grayscale image as a mask (darker = less selected) with full intensity edges along the cliff fading out to black as you get farther away from the edge.