[WIP] This Orb: world-building and mapping project

[jwbjerk]

OK, in trying to move on to the next step, "elevation" i've hit a couple problems. I looked through all your tutorial threads (at least looked at all the titles), found some good tips, but ultimately didn't find the answers to my problems.

1)
I'd like to create a realistic elevation map, along the lines of this:


I have the elevation roughed in some detail like so:


But obviously the level of detail is dramatically less. The obvious ways i might try to achieve the effect are mind-numbingly tedious, and i don't want to embark on one of those paths if there might be a better way.

a) Paint it by hand: tedious, but eventually i'd get what i want
b) Copy/Paste bits of elevation from our world: possibly faster, but getting stuff to match with my coastline, and planned mountain locations may be impossible.

It looks like some people use Wilbur to make erosion-effects, but that's a Windows program, i have a Mac, with limited Windows emulation, which can't handle Wilbur.

Advice? Helpful suggestions?

No matter how i do it, i'll probably retouch some of it by hand. Can anyone recommend some good custom brushes for this kind of effect?


2)
I also seem to have a chicken-or-the-egg type problem. Looking over Earth's elevation map, i get the impression that erosion patterns are much more strongly defined in wet areas than dry ones. But of course you need to know elevation to figure out your rainfall patterns. Is the difference really going to be significant on a global scale? How have other people dealt with this?

[Guldaroth]

I also seem to have a chicken-or-the-egg type problem. Looking over Earth's elevation map, i get the impression that erosion patterns are much more strongly defined in wet areas than dry ones. But of course you need to know elevation to figure out your rainfall patterns. Is the difference really going to be significant on a global scale? How have other people dealt with this?

For the first question, I'm sorry, I just got the same problem of detail level...

But, for your question, I talked with a geologist about such a similar matter. He said to me that the erosion patterns could be approximate this way: In the beginning the erosion is quite everywhere the same. What really matters is the geological soil. On a long scale it tends to diverge from regions to regions. For exemple after at a certain time, a region will be quite flat because of its soil which is far more tender than another region. And so you've got the first step to define your rainfall patterns! I think you'll have to work those question together.
I hope I was understandable enough...

[jwbjerk]

But, for your question, I talked with a geologist about such a similar matter. He said to me that the erosion patterns could be approximate this way: In the beginning the erosion is quite everywhere the same. What really matters is the geological soil. On a long scale it tends to diverge from regions to regions. For exemple after at a certain time, a region will be quite flat because of its soil which is far more tender than another region. And so you've got the first step to define your rainfall patterns! I think you'll have to work those question together.
I hope I was understandable enough...

If i understand you, you are saying i shouldn't worry about eroding high rainfall and low rainfall areas differently, because climate and rain patterns vary, and at some point in the past all the different parts of the planet will have gotten some rainfall. Is that right?

If you have access to DEMs then B is the way to go...just copy n paste and blur n paint until they fit seamlessly. Otherwise you're with the rest of us looking for a way to emulate a DEM...finding some techniques or doing it by hand. On the erosion, it shouldn't matter too much for a world map because you can only get so detailed in the image. By and large the rest of us just use informed guesswork and make it up as we go.

Is there any different between a "DEM" and a "bump map", like these: (1. Terrestrial elevation data)? He's labeled the 16bit versions as "DEM"s, and the 8bit version as a "bump map", but i would have called them both "bump maps". Maybe you would call them both DEMs?

16,200 pixels wide is the largest i've been able to find a bump map, and while it's 4x bigger than my map, would anyone recommend working from something larger (if it's available somewhere)? Seems like my elevation might be much less obviously part of Ethiopia (for instance), if i copy/pasted a piece that was more zoomed in. Of course the scale of the features would have been changed, but i expect such geologic features are "fractal" enough, that they look similar at different scales.