WIP: Erobelis Isle

[wdmartin]

I'm working on building a tropical island with a central volcano using Photoshop and Wilbur, and having a rough time of it. Here's what I've got so far:

The height map


After processing in Wilbur


I've been following Arsheesh's Eriond tutorial, albeit translating the instructions to Photoshop as I go. It's been very helpful. But as you can see, the results so far aren't quite what I'm aiming for. It's a problem of scale. The entire island is supposed to be about 45 kilometers at its widest point; but it comes out looking like a continent. For reference, I borrowed the basic size and shape from Efate, in the Republic of Vanuatu.

I'm also not sure what to do about the calderas on the two volcanos. Logically they ought to be lower than the surrounding ridges, but then Wilbur treats them as a basin and starts adding rivers.

What should I be doing differently? And advice would be appreciated.

[Deadshade]

Yours is a quite difficult question.
Actually I consider that getting reasonable scales that the eye interprets correctly is the most difficult problem in realistic, relief 3D mapping. Doing only 2D more or less symbolical maps frees of all these problems so that this is a simple solution to your problems.

More in detail why happens what you see happening.
As you want to show relief (e.g 3D) you are necessarily confronted to the question what the scale of this 3rd dimension is, compared to the other 2 usual horizontal directions.
For instance suppose that you want to show a 2km high volcano ridge on a map which is 40kmx40km in 4000x4000 resolution.
So horizontally you get a resolution of 100 pixels/km.
Suppose that the volcano's outer slope is 30° and its inner slope is 60°. That means that if it is 2 km high, the basis of your rim is about 4.7 km. And that means that it takes 470 pixels !

Now you understand what the eye is doing with your map - it sees a volcano like shape and interprets the rim as being a few km wide. Then it sees the whole map which is some 1000 times bigger and concludes that the map's size is a few thousands km.
All that happens of course subconsciously. Btw the same trick happens with rivers too - your eye considers them big and concludes that the whole map is big too.
That's why you "see" a continent and not an island.

So what you need is to make the width of the rim about 1/10th - 1/20th of the size of your map if the whole map is supposed to represent some 50 km or so. You also need less and wider rivers.
Of course that is something that you won't get by using the ridged multifractal with standard setting. This setting is adapted to continental scales so that everything you'll do will look like a continent (that's where Wilbur is basically good).
If you want to represent much smaller scales than continental, then you must change the fractal setting and unless you really master the underlying maths, you have about 0 chance to find the right setting.

My personnal solution to this problem is that when I want to do a realistic relief map with a size of less than a few 100 km, I simply draw it by hand.
I use then eventually a fractal software (like Wilbur) with specific setting only to get realistic textures on specific places of the map.

[su_liam]

The feeling of this, to me, is of the high pass of an island map. Basically, your high frequency data(the small features) is good, but you lack the dominating low frequency/large features. The calderas(calderae?) should be at the top of broad shield volcanoes presumably. There should thus be a broad, roughly conical rise toward those. I'll try to put up an image of what I'm talking about when I get a free moment this morning.

This is a very recent insight that may help me with my usual continental/global-scale work. Thanks for that!

[acrosome]

Yes, I think your problem is that there is no volcano there as you intend. Instead there is a very odd circular ridge. The whole island needs to (generally) slope up to the caldera. Waldronate posted all of his Fun With Wilbur tutorials to this forum, and he includes one on making a nice volcano. Follow the link.

As far as keeping the caldera from eroding, you can select around the caldera, invert the selection, and then run erosion cycles. Essentially, you select everything but the caldera.

I'm away from home, but I'm also pretty sure there's a way to "stretch out" the relief so that your map looks higher. Do that and a few erosion cycles and it might look fine.

[wdmartin]

I definitely need to read those Fun with Wilbur tutorials. I found a couple of them in the Wayback machine, since the site is currently down, but I didn't realize he'd uploaded copies here. Also there are more there than I was aware existed.

I played around briefly with the exponent filter, thinking that might be used to add height to the terrain. And so it might, but I guess I don't know how to use it yet. This is my first attempt at doing anything with Wilbur, so there is much yet to learn. I'll keep plugging away at it.

This is actually the third attempt at this island. The first two were even less successful, and involved using an SVG topographical map of Efate from Wikipedia. The creator apparently generated it from DEM files following a series of French-language tutorials on working with DEMs (links all at the bottom of the page, labeled "Les didacticiels pour la cartographie numérique géoréférencée"). I spent a lot of time in Inkscape separating out all of the terrain heights into layers, with the theory that I could then build a height map in Photoshop by converting them to greyscale, assembling them into layers, and using a combination of gradient overlays and airbrushing to get a smooth transition across elevations. I figured that'd give me a the gross features of the terrain, and then I could add details via noise, rendered clouds, and so on.

The theory was nice, but dang, putting it into practice was hard. I kept winding up with strongly expressed steps in the terrain once I got it to Wilbur. So I went back to photoshop, blurring and smudging and feathering and burning like a mad man, only to find the steps still there on the next attempt. After a few cycles I decided to try a different approach -- hence this post.

[su_liam]

First thing you are going to want to do is have your elevations taper off toward zero at the coast. Except where you want cliffs of course. I'd try using a brush set to Multiply and a very bright grey to gradually paint down around the edges.

Next, select the entire island landmass. Put a small mound on that selection with the operation set to add to raise the entire island reliably above sea level. Tap the Edit Profile button to make a somewhat flat-topped mound. Stroke along the upper-left corner to raise all the upper values to maximum, and, from the edge of the area you flatten try to stroke downward and to the left to make the falloff as smooth as possible. Try the Smooth operation several(many) times to make it a bit smoother, and apply it with a minimum set to 0 and a fairly small maximum

After that, select a nice large area around one of the calderas. Use the mound tool with the profile edited to an even flatter top, and the operation remaining on add to build the volcanoes around the calderas. You might use the mound tool to add in some other, lower hills.

I'd try it, but I'm overdue for a new computer and Wilbur tends to get realllly sllllooooooowwww with a heightfield that high resolution. Besides it's an 8-bit jpg. Not really worth the wait. I tried it on a quickly thrown-together map with some hasty-pudding noise. You shouldn't need as much noise, since you already have a decent high-pass layer. Hopefully you have at least a 16-bit version somewhere...

Don't forget to find your sealevel!

[wdmartin]

Interesting. Thanks, I'll give it another go.

EDIT: Could you elaborate on what you mean by "don't forget to find your sea level"? I don't know how to do that, or why I should.

[Deadshade]

Below a way how to do fast a volcano (took about 10 minutes with Wilbur) with right scales.

1) Do the island shape - altitude doesn't matter.
2) Most important step : Hand select an irregular annular shape. The width of the ring must be consistent with the overall scale as I explained in the post above. FEATHER ! I did 3 times sigma 3.
3) Filter>Fill>Mound. I added 2% noise. Operation Add. Select use fractal. Fractal parameters - I used ridged multifractal, H=0.9, radius 1. You may play with radius, H and scaling if you wish. Also test another random seed if you want to try other shapes.
4) Deselect.
5) Filter>erosion>precipiton. I did 5 passes with Max length 64.
6) Filter>erosion>incise flow. I used Effect blend 0.5, Preblur 1.5. You may experiment depending on how deep and wide you want the incises.



After that you can select the landscape around the volcano and fractalise it as you wish adding hills, rivers and what not.
Just a remark - as you don't want rivers in the caldera, do this work by selecting the island excluding the caldera.

[wdmartin]

Okay, I've taken another stab at it.

I went back to the drawing board on the height map, and came up with this:



This was based on the elevation data for the real-world Efate Island. I had 13 layers representing the elevations. The bottom most was solid #333333, the next up was #444444, and so on up to pure white (#FFFFFF) at the top.

Then I gaussian-blurred the heck out of the edges to make them blend more smoothly, and loaded it up in Wilbur.

I don't remember what all I did in Wilbur. There was much adding of noise, and some erosion. But basically I just kept doing things to it until I ran out of buttons to push. Here's the result:



And that's as far as I've gotten. I opened up the PNG height map in Photoshop and stalled out. Arsheesh's Eriond tutorial was written for Gimp, and as far as I can tell, Photoshop lacks a Bump Map plugin like Gimp's. I've tried googling for an equivalent, and so far all I've found are lots and lots and lots of tutorials about how to make bump maps in Photoshop for use in other programs. But nothing much on just doing one directly in Photoshop itself.

I'm experimenting with gradient maps, but it feels like I'm flailing. And the game's next Saturday ... eep ...

EDIT: Hours later, a further WIP:



Starting to come together, a bit. Still not satisfied with it, but I'm not sure what else to do to it (besides doing something to make the ocean less flat). And game day is only 7 days away and I've got a half dozen other maps that need to be made ...

[su_liam]

I've been messing around with creating shield volcanoes with, I think, some success. It's basically a composition of flat-topped Mounds with some flat-bottomed negative Mounds for calderas. Most attempts I've made at adding lips to the calderae have been dismal failures. I'll post my WIP and if I get this working better I'll post a tutorial to the technique, though I suspect most folks here could work it out from the description.

I'll also let you know, 8-bit heightmaps are of dubious value. You can work in 16-bit on every version of PS after 7, which is pretty good. I know 32-bit float was available in CS3, though on the lab computer at the University it was crashy and unreliable. On my computer, CS4 can work with 32-bit float pretty handily. Wilbur works in 32-bit float by default. In any case, I'd avoid jpeg like the jplague for this porpoise.