View Full Version : From outline to world via FT/Wilbur
04-11-2012, 01:17 PM
I have sketched an outline of a region on paper. I know where I want my mountains.
I know how to use Photoshop very well. I know how mountains, rivers and erosion work. There is no way I'm gonna do this by hand.
How can I use Fractal Terrains and/or Wilbur to flesh it out? How do I make the terrain random? How do I make a smooth transition to water (staying true to the outline)?
I would like to use Wilbur because I want to create realistic erosion and rivers. I've just gone through an awesome tutorial taking a Fractal Terrains map and using it in Wilbur to make realistic terrain.
It seems that without the random goodness of FT I am lost! But I really want to use this outline I've drawn.
I have tried a tutorial on the Wilbur creator's website. I have also tried applying fractal noise with a multiply setting - whether I'm on the right track I have no idea, because the rest of the settings are gobbledygook. I tried introducing randomness via Photoshop, the Clouds filter, but when imported to Wilbur this makes my land look like slices of bread stacked up.
Is there a tutorial that does a good job on this? Surely it's a common task (outline to realism), but what I've seen so far ends up looking ridiculous.
04-11-2012, 08:42 PM
Well I've never used Fractal Terrains, or Photoshop for that matter, so I can't speak to the first part of your question. However I have worked quite a bit with GIMP and Wilbur, and in my experience (Fractal Terrains aside), it is no easy task getting random cloud patterns to match up with your outline. However, it is possible to generate random cloud patterns in GIMP (or Photoshop) for both your land, and separately for mountains, use the Free Select tool (or whatever it's Photoshop counterpart is called) to select portions of clouds from your Mountains clouds layer, and then copy and paste them onto another layer above the layer of your Land clouds layer. From there you just fade the edges of the Mountain clouds and then use your Airbrush tool (set at low opacity) to sculpt the surrounding terrain to fit these mountains. I recently wrote a tutorial (http://www.cartographersguild.com/showthread.php?18280-Eriond-A-Tutorial-for-GIMP-amp-Wilbur) on this process. Of course, if you are planning to generate the clouds in Fractal Terrains, then I'm afraid I cannot help you there.
04-11-2012, 11:50 PM
I recommend http://www.ridgenet.net/~jslayton/FunWithWilburVol4/index.html (and the newer http://www.cartographersguild.com/showthread.php?18120-March-April-2012-Lite-Challenge-Entry-CSU-Johnsondale-s-New-Found-Lands has a PDF near the bottom of the first page) combined with http://www.ridgenet.net/~jslayton/FunWithWilburVol5/index.html to get some lakes and river markings. If those aren't helping, I could probably do a few more examples, especially if you show the kind of source material that you're working from.
04-12-2012, 12:44 AM
Your PDF attached to the March/April challenge is promising. I'll give it a go. I tried the Fun with Wilbur, Vol 4, before.
I'll have a shot at it tonight. 100 passes with the precipiton tool! Fingers crossed for results.
While you're here - when should I use precipiton vs incise flow? I've seen a tutorial with countless incise flow steps, but only a few precipton steps.
04-12-2012, 02:23 AM
The incise flow tool is good for global activities when you want to do lots of damage to the terrain in a hurry. The state of the whole surface is used to compute the number of cells that can flow into each pixel and the logarithm of that result is subtracted from the altitude (result = amount * pow(flow, flowExponent) if that helps any). The results look plausible when viewed from an overhead perspective, but those little canyons tend to be far more deeply incised than would occur in the real world. For best results, it also requires a contiguous flow field, meaning that the fill basin operation is more or less mandatory with this operation. Fill basins has its own little issues that affect the character of the surface, of course; most obvious is the lack of basins following a fill basins operation.
In contrast, the precipiton tool is more of a local tool that acts globally, if that makes any sense. It's implementation is a little automaton that gets dropped onto the surface at a random point and then moves downhill, pushing a fraction of the difference in altitude to the lower altitude. For each "pass" of the filter, that little automaton gets dropped onto the surface a number of times equal to the number of pixels in the image and it plows its way downhill. It doesn't try to figure out a global state and work from there. It also doesn't care about a contiguous flow field because the automaton stops as soon as it hits a locally low spot. Like a swarm of ants eating away at the surface to get a final effect.
When to use which one? It's a matter of taste. For folks who just want a fancy-looking bump map, noise+basin fill+incise flow is probably all they need. For folks who want pretty DEMs, precipiton erosion may be all they need. I tend to use incise flow to rough out things and follow up with the precipiton operation to make the slopes a little more plausible. I have a tendency to want to use a 3D/isometric view on maps and the precipiton shader gives a more plusible result for final finishing than those deep, deep canyons.
A couple of examples that show a basic isometric view derived from the output of basic Wilbur processing are http://www.cartographersguild.com/showthread.php?11379-New-Same-Old-Thing and http://www.cartographersguild.com/showthread.php?4676-March-Entry-Excess
04-12-2012, 08:02 AM
Thanks waldronate. The deep incisions, while great from a distance, were concerning me. I've just done 5 precipiton, 1 gentle incise, then 10 more precipitons.
Here I've got a clear demonstration of precipiton in action - it's filled an entire gulf and built up around the exit of a river in the north. It's a pretty good model of alluvium, I just didn't expect it on this scale. Sea level / manual tweaks will fix this up easily.
My mountain chains were added using arsheesh's tutorial, not waldronate's March/April one. I think my mountains are going to disappear soon; I might try starting with big chunks of high ground, next time.
EDIT: Incise flow, with an appropriate blur setting, seems a good tool for producing glacier-affected landscape like sharp mountains and jagged fjords.
04-12-2012, 10:37 AM
The erosion scale is important to get a "realistic" effect (both erosion types are pure fiction, so any realism they appear to bring is in the eye of the beholder). The precipiton erosion results in maps that have a "natural scale" of around 1 to 50 meters per pixel. Beyond that and the effects just aren't visible. The incise scale erosion doesn't really have anything that resembles a "natural scale", but is too is mostly useful for local areas. Both of the erosion types look most natural for maps up to a few tens of miles across (maybe hundreds if you want to stretch it). I find that trying to use those operators for continental-scale terrain gives results that just dont look "realistic". They certainly look good, but in a more abstract sense when applied to larger areas.
I mention this because extreme fill at the edges of continents as you saw really shows up the lacking areas of the processes. This level of fill is typical of smallish areas in the real world rather than huge areas. The easiest way to reduce the fill amounts is to add an underwater slope away from the continent by taking your original land mask, inverting it, and then using Filter>>Fill>>Mound with a low of 0 and a high of a negative number (say, -255). The precipiton erosion can then carry plow terrain down into the sea instead of piling it onto the sea surface. If you already have coastlines that you don't want modified, just keep the land selection active during the precipiton actions. That way, the fill will get clipped off at every iteration.
04-12-2012, 08:26 PM
The mountain shapes look OK, it's the valleys in-between that are devoid of any texture. I'm not sure how to address this (with so many passes of precipiton this seems somewhat inevitable). Perhaps selecting basins, adding more noise (10%) and then another few passes of precipiton might fix this, although it might not. Not sure.
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