[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?