Tackling the terrain of my worldbuilding project

[Rubikia]

Hi all! I have worked on this project for over a decade at this point, and I have posted a few of those maps here even, and over the last few years when I have been using Inkscape to make maps for it I have been expanding and standardising the terrain and river systems. With each new map plate I add a load of extra rivers, meaning that the main continent over time will be full of rivers.

I knew that I would like to have a relief map-esque thing for this setting too, and I had experimented with contours (left) years back which looked pants, and then I used Mazlo's mountain sets to give it that look (right), but Inkscape isn't the best programme to use set effectively, so I decided that I should move on to a programme much like many others here, the magical endless opportunities of Wilbur.



I have general ideas of where the mountains are, but I have rigid ideas of where the rivers are, so I wanted to use Wilbur to generate the mountains in their higher areas and maintain the river systems. I followed a few tutorials from the Guild, like CSU Johnsdale and waldronate's step-by-step of river masks, and I produced these black and white masks of the Land, basic hills, basic mountains, and the river mask.



I opened the land mask, and then Select>>Load Selection for the hills and Filter>>Mathematical>>Offset to 20, and I did the same for the mountains and set the Offset to 40. I then Select>>Load Selection for the rivers, inverse select, and set the Offset to -40, like in waldronate's aforementioned tutorial. This should have meant that the rivers were cutting deep into the land and mountains, at least that is what I expected.



I then Select>>Load Selection for the rivers mask, and did not invert, so that I was selecting all the land around them. I added 10% noise, and then proceeded with Precipation based erosion at 25 passes.



This looks okay, but it's not right yet. The only problem I am seeing is the dreaded blue appearing on the coasts... I am also 98% sure the rivers that I supposedly cut deep into the land aren't having an effect at all.

I then did 4% noise, 25 passes, 2% noise and another 25 passes to produce this (left), but then I went to Filter>>Mathematical>>Exponent and set it to 2 like the CSU Johnsdale tutorial (centre). I had a feeling that it was an issue selecting using the river mask, not the land mask, so I repeated the last step with the land mask (right)



Not going to lie, I'm quite sad that the rivers are going wild and aren't how I wanted them on the left! But in the middle, it's to the other extreme! On the right it is not as bad, but the blue edges along the coast are persisting, even getting rid of islands completely, and it doesn't look that good.



I'm not 100% sure what I did wrong/the best way to go forward, but I will continue trying. I suspect it is actually the offset that I set at the beginning that is wrong, so maybe I will have to experiment with it.



Anyway, this thread will cover my Wilbur escapades and fails, as well as how I expand my rivers and the terrain in general as I update the base map and create more map plates.

EDIT: I tried this process a few more times and the blue outline continues to show up, its almost as if wilbur is receding my coastlines which is unfortunate. I thought that when you have the land selected it wouldn't do that, but I guess not.

[waldronate]

Precipiton erosion in Wilbur moves altitude from high to low. If the oceans are well below 0, then the land (at or above 0) will get smaller because some of the altitude is moved below 0. If the oceans are at (or a very, very small below) 0, then land will get larger as altitude builds up around the edges. If you keep a selection and run the oceans at 0, the land will hit the edges of the selection and stop. In this case, areas of rapid altitude transport will grow cliffs because Wilbur is doing the precipiton erosion and then blending that result back to the main surface through the selection. If you keep the ocean at 0 until the last run, then set the ocean down a bit on that last run, you'll get nice and crinkly edges. If you keep the ocean down and use height clip with low=0.01 and high=10000000 after every erosion pass, it will ensure that your coastline always exactly matches your mask.
One trick to force rivers to where you want them to be is to make a mask that has just your rivers on it. Use that mask to punch down the rivers (load the river mask as a selection and either set to 0 for subtract some amount, the load back your coastline selection) once in a while and the precipiton erosion algorithm will keep finding those rivers as the low spots, forcing the rivers to flow that way. They may eventually become ingrained enough that you might not need to keep punching them down a lot.
Erosion in Wilbur is a relatively untamed beast: as long as you keep a close eye on it and regularly apply the lash of masks as needed, it will do a lot of the heavy lifting of detail creation for you. If you let it do its own thing without much supervision, it will try very hard to get to its desired end state: a flat plane.

[Rubikia]

Thank you waldronate! That seems to have worked quite well to keep the coastlines intact!

The rivers are also embedding far better when after using Filter>>Fill>>Set Value to zero too. Obviously it isn't completed, but I think that either the heights of the mountains compared with the land needs to be increased, or I should continue to add rivers in order to influence the terrain generation more. Right now, the basins are pretty flat and ordinary so I think that I need to add more rivers, or some extra hills, to make it more interesting.

[waldronate]

You need more noise. The current Wilbur version has a median filter to kill it later if needed. An exponential operation at the end can also help. Having a mask with both coastline and rivers during erosion can also for rivers more strongly.

[Rubikia]

I took your advice to heart Waldronate, and added a lot more noise for the first set of erosion on the next version!

But before I did that, I wanted to flesh out the rivers of the south-western peninsula to help Wilbur for the generation in that area, so I completed this map plate of 'Upper Sirntar' (left). This has meant that most rivers on the continent are now plotted out, but there are still some blank areas. I've put boxes over where I have recently made maps of which include rivers (right). Maybe I'll use Wilbur for inspiration.



Anyway, I used these new rivers and such to update the masks for Wilbur. I set the offset of the hills this time to 40, and the mountains to 80, and similarly set the fill value of the rivers to 0. For the first batch of noise, I set it to 100, and ran 25 passes of erosion. I then did 10% and 25 passes, and 5% and 25 passes. Then lastly I set the exponent to 2, and got this, which I am pretty happy with so far.



It is still a bit plateau-ey but it's slowly getting better, at least I think.

EDIT: Actually, looking at it, the rivers that appear on the heightmap are almost white/far whiter than the valleys and that which Wilbur generated, so it seems that the river height is too high somehow. I'm not really sure how it can be high, but also embed itself into the rest of the landscape.

[waldronate]

Precipiton erosion works better with larger altitudes (10000+ is a good place to start). The very smooth internals are due to a whole lot of precipiton erosion without adding noise back in.

[Rubikia]

I had a go at using higher altitudes with crazy large percentages of noise, but unfortunately, it just left a vast majority of the landmass undetailed and flat. Instead I tried again with the same thing I did last time, though I added an extra step.

I set the offset of the hills this time to 40, and the mountains to 80, and the fill value of the rivers to -1 this time, then I set the height clip as Waldronate recommended. I then generated noise at 100% using the river mask, and then applied 25 passes using the land mask. After that, I selected the rivers again and inverted, setting its fill to -1. Then I applied 10% noise using the river mask, set the height clip again, and ran 25 passes using the land mask, and repeated these settings afterwards but with 5% noise. It's on the whole looking better I think with the rivers no longer starkly visible on the relief map, and also they're mostly affecting the terrain too.



I also made a quick mockup map of the continent using the heightmap and the rivers too, I personally like how it's looking so far.