Rivers and lakes with Wilbur

[Akirus]

Hi there, fellow cartographers. I've been browsing through all the useful information contained in this forum for a long time and finally decided to make an account to seek assistance on a snag I've hit with my most recent map. I've followed Arsheesh's Eriond style tutorial to produce the attached height maps. I deviated from the instructions a little bit and used a land mask to keep all the operations on the land only, and changed some of the numbers for the incise flow process because the dimensions of the map were significantly larger.

My problem now is that whilst the product from Wilbur looks fine, I don't want as many rivers as it has given me. I'd like to be able to set the frequency/size of rivers based on regional rainfall/climate. So for example, the northwestern part of the map is supposed to be a dry and cold region, not awash with rivers. I'm not sure the best way to go about this. I considered either selecting only certain parts of the map to apply the incise flow operation, or perhaps just putting the Wilbur output into Photoshop and manually drawing on the rivers I'd like to keep. For the latter method, I'm not sure as to the exact methodology I would even use, since even if I traced the rivers onto the original pre-Wilbur height map, it doesn't look the same at all. Does the incise flow operation have an effect other than creating the river gaps in the terrain?

The other thing I'm struggling with is figuring out how to add realistic lakes to the map. Eriond's guide makes no mention of this point and I had no luck getting it to work following Fun With Wilbur Vol.5 (?). I really have no idea the best way to do this so any guidance on this point would be greatly appreciated.

I'm sure there are other methods to do this, but I've already put in a lot of time airbrushing the current height map so I'd like to make something of it, if possible. I've read all of the Wilbur guides and dug for as many threads and comments as possible but I'm getting pretty lost and frustrated so I figured I'd try my luck asking for some tips. Thanks for taking the time to read.

[waldronate]

The incise flow operation lowers all of the land by an amount proportional to a power function of the number of upstream samples at a point. Therefore, it lowers just about everything on your map.

Wilbur needs a median operator, but I hear that the developer is too lazy to get around to implementing one. I don't recall if Photoshop lets you brush with a median filter, but that would be a good solution.

One way to reduce the number of incised channels in an area is to select the area, feather the selection, and then use Filter>>Morphological>>Dilate followed by Filter>>Morphological>>Erode. Use a value of 1 for those and it will completely close up the small rivers.

If you've done the basin fill step, then you won't have any lakes left because fill basins fills up all the basins where lakes would form. You can paint in a basin by hand and then use the techniques of Fun With Wilbur, Vol 5.

Wilbur also features a river finder feature (Texture>>Other Maps>>River Flow). It lets you find rivers without having to incise them into your terrain. One way to make rivers that is a little more controllable is to follow the instructions of https://www.cartographersguild.com/s...t=33087&page=2 (about halfway down). The idea is to make an image with white rivers and black background, load that image as a selection, set everything inside that selection to 0 height, and then use precipiton erosion to clear things out a little. This same technique can be used to get basins for lakes (you can set them to something other than 0) wherever you want them.

[Akirus]

Thanks for the help, Waldronate (and for making Wilbur in the first place). I spent a day or two trying out your suggestions with varying degrees of success. If you don't mind, I was hoping you could answer some followup questions.

I followed the instructions in Arsheesh's tutorial to erode the terrain until the step before Incise Flow. Then I used Texture>>Other Maps>>River Flow to calculate the rivers, which I put into Photoshop and traced the rivers that I wanted onto a black/white mask like you suggested, as well as some lakes. I tried to follow https://www.cartographersguild.com/s...t=33087&page=2, but every time I apply precipiton erosion, it gets rid of the lakes and a lot of the rivers. Am I supposed to apply these steps (add noise (25), fill basins, incise flow (amount=2, exponent=0.2), and then about 30 iterations of precipiton erosion) to the whole land mask or just the rivers/lakes? And does it matter if I do the rivers/lakes together? Everything I try seems to lead to the same problem.

Also for Fun With Wilbur vol.5, I'm a little confused about the last few steps. What formats am I supposed to be using from Wilbur->Photoshop and back again? I tried multiple times and I never managed to get anything resembling the pictures in the tutorial. The best I could do was fill the lakes black on the height map but I'm pretty sure that's wrong (attached examples). Any other way I try it, the lakes just end up being land. And even with the example I posted, any time I try to use precipiton erosion, all of the lakes get filled in anyway.

[waldronate]

The noise/fill basins/incise flow loop is intended for the land areas that you want to keep. You can do this loop with a mask that just allows the loop to affect the land by using white on the land and black on the sea / lake areas. 30 is a very large number of iterations. It's certainly no surprise that your detail is disappearing with that number of iterations. Wow.

The simplest format to get from Wilbur to Photoshop and back again is Windows BMP. PNG also works well.

I took a detour to demonstrate some of the techniques. It's in a zipped PDF because regular PDFs are disallowed for some reason. I also attached a 3D view of the end of the process.

[Akirus]

Your posts are always so helpful, thank you for all the time you put into the pdf. I wanted to give it a thorough go so I spent a few days working on drawing a good river+lake mask before starting on your guide. I put in way too much effort just drawing out the major rivers I wanted after dividing it up into drainage basins, but I gave it a shot with just that and I got pretty good results on my first few tries. I'm going to draw in the smaller rivers and tributaries to the mask and then take another crack at it. The extra control over the details afforded by using masks is nice.

Do you have any tips for getting more variation in the 'flat' parts of the map? The final output looks good but the surface is a bit uniform from mountain to coast, other than river incisions. I tried using the original difference cloud-based heightmap as the base and it went okay, but by the end of the process a lot of the detail had been flattened out by the erosion. With that method, I also tried using percentage noise (5-10%~) instead. I'm sure if I had more small rivers in there, that would help too since Wilbur would erode them into valleys. I considered making different masks for highlands, plateaus, etc. The mountains seem to get flattened a bit too, what would be the best way to counter this? Is there any benefit to adding more height layers for the mountains, or perhaps offsetting a wider range of heights?

I also tried using a higher resolution, since I need the detail for other purposes later and I don't mind waiting longer for the processing. I've been using 11078x6640 (original), 5539x3320, 2770x1660, 1385x830 and 692x415. Do you have any suggestions for varying the values for the operations at higher resolutions? I tried increasing the Amount value and adding pre/variable blur on Incise Flow at higher resolutions to prevent things from just disappearing, but I'm not sure if I'm on the right track there. Maybe it would also be worth adding another resolution sample between the last 2 since the jump is pretty big.

Edit: After playing around with it a lot, here's what I came up with. Since I put in a ridiculous amount of time into the river/lake mask, I wanted to keep it accurate to my selection. Incise Flow would make a lot of unwanted river channels so I just used a combination of the river mask + precipiton erosion. I then generated a height map and overlaid the river+lake mask to get something that I think looks okay. I'll keep working at it tomorrow.

River Mask


Heightmap

[Akirus]

After tweaking the numbers a bit, I came up with something I'm satisfied with for the time being. Here are the results and the methodology I followed in case anyone reading this is trying to do the same thing:

Original height map created by following Arsheesh's tutorial up until the Wilbur section.


Land Mask


I then used some noise and precipiton erosion, but instead of Incise Flow, I used Texture>>Other Maps>>River Flow and imported it to Photoshop. I recalculated it again with longer rivers and imported that too. Then I deleted the backgrounds and put the two River Flow layers on top of each other with different colours so I could get a better sense of the length/scale.

Wilbur does a really good job with creating realistic rivers, but I only wanted them in certain places (eg. no sprawling river networks in the middle of a desert) so I set to work in Photoshop erasing the rivers I didn't want. I had separate layers for the major rivers and smaller rivers, which I determined using the Wilbur River Flow renders as a guide and dividing them up into different drainage basins. I doubt my specific criteria is meaningful since I chose it arbitrarily to suit my needs, but here is a rough progression of what I did.

Overlaid Wilbur River Flow renders with different colours looked something like this.


The river/lake mask I created.


I imagine you could also just draw your own rivers and lakes however you want, but I figured I'd get better results letting Wilbur decide the shape of the river.

I then loaded everything into Wilbur, cleared out the rivers/lakes using the mask and used some combination of percentage noise, fill basins and precipiton erosion. The erosion would kill the waterways pretty quickly so I used the river/lake mask to get them back in place a few times. I found that if I set the river/lakes to fill -1, the channels would be cut really deeply like in the attempt from my previous post, so after doing that for the first one, I used various offsets on subsequent rounds to create a more subtle effect. Also height clipped the land/sea using the land mask where needed.

The resulting height map from Wilbur.


Since the erosion from Wilbur lined up really nicely with the original river/lake mask, I just used that and overlaid it in Photoshop.

[waldronate]

I missed your post from a couple of days ago, but it looks like you've achieved results roughly in line with what you were hoping for.

The use of a couple of masks to get different results for incising rivers into your terrain (setting a value through a mask to lower the terrain is the same technique that Incise Flow uses, except that Incise Flow computes the mask dynamically) can also be achieve by using a single selection mask with multiple grayscale levels. Lighter colors will get more effect. If you use Texture>>Other Maps>>River Flow with a black solid background, white as the river mouth, and a dark gray as the river source. Using that texture as the river mask will let Filter>>Set Value achieve its maximum value at the river mouth and its minimum value at the river end. For example, is you have such a grayscale mask with white [RGB(255,255,255)] at the river mouth and dark gray [RGB(31,31,31)], offsetting by -100 will push the terrain down by 100 units (255/255*100) at the river mouth and by 12 units (31/255*100) at the river ends.

I always admire folks who take the time to draw complex masks because they will get very good results if they use those masks in Wilbur. I lack patience for drawing complex masks, though, and rely on procedural generation techniques from minimal inputs. I'm willing to accept slight variances in the results, which many people won't.

[Akirus]

Ah, it never occurred to me to use grayscale levels on the river mask. I'm curious how different the results would be but I think I'm too lazy to go back and redo the river mask since I already spent a few full days on it. The method I used was to use a 2px pencil to draw in where I wanted the major rivers to be, and then using the 1px line from Wilbur for the smaller ones (erasing the rivers I didn't want).