Thank you all for your civil discussion of this challenging issue. There is no way around it, documentation for Terragen is indeed lacking, and not properly updated. This is something that weighs on us every day, and I sincerely apologize for the scant or difficult to understand information you are often confronted with in referencing the docs.
I can't offer any easy comfort or quick solution, nor anything new that hasn't been said before, I'm sorry to say. As a number of you have identified, Terragen is in itself a difficult program to document due to its open, flexible nature, and the unique workings of some of its proprietary functions such as cloud shading, terrain displacements, surface shading effects, etc. In addition to that, we are an even smaller team than ever (someone said 3, technically we're 2, with very part-time input from a 3rd person), and only one of those people (Matt, the founder and software architect) truly understands certain things well enough to properly document them. Unfortunately that means either he splits his time between dev and docs, or he focuses on dev and the docs don't get updated in some of the more complex areas (e.g. what exactly do all the v3 cloud settings do).
One part of the solution is to ultimately hire one or more additional developers, which we intend to do, as well as potentially other staff to handle documentation in a more dedicated way. Terragen 4 has provided some of the foundation to make this possible in a business sense, and I am hopeful we can move in these directions soon.
We have also tried working with a number of educational content developers over the years, but only GeekAtPlay actually came through with delivered content. That has frankly been quite frustrating, but we remain hopeful that the increased ease of use of TG4 and the new Educational License Program will result in greater availability of educational content in the long-run. We're in talks with a couple of content developers to that end.
In the meantime the ideas around user contribution to the Wiki that have been discussed here are indeed how we had hoped it would be used. Unfortunately we had a spammer attack recently and we are still cleaning it up and have had to close open contributions for now. We intend to bring the wiki back to more open access in the near future, after we clean up the spam, and at that point we'll be working hard to bring things up to date for TG4. We're hopeful that some of you will be able to contribute as well with the more specific problem solutions that often come up here in the forums. Structuring that information will no doubt be challenging, but just having the solutions - rather than the entire discussion chain to find it - documented in one place, with reasonable titles, would be a big step forward. We don't assume people will contribute, but we do hope that some will, as the work of documenting all solutions to problems and techniques discussed thus far is too great for us alone, for now.
We want Terragen to be as accessible and easy to use as possible and we recognize it's not there yet in several important ways, including major aspects of the UI and interaction, as well as the documentation. We continue to work on improvements in those areas. Thank you all for your patience, understanding, and support over the years.