First, the good news! With the release of the Rage Toolkit on Steam, modders eager to get into the guts of the game now have the software to do so. The bad news? Only "technically sophisticated and adventurous" modders need apply, it's a 35GB download and cooking up your own Megatextures will demand a level of patience beyond what's mentally possible.
Besides games that have built-in tools for creating content (LittleBigPlanet, say), injecting your own creative juices into your favourite titles usually requires a bit of technical or artistic expertise. I don't think anyone expected Rage's world-building tools to upset the trend, but they sound high up on the curve, going by the announcement post on Bethesda's company blog:
Before you start downloading the hefty 35+ GB file, the RAGE team has provided some documents to read. As described in the welcome document, these tools provided are complex and aimed towards "technically sophisticated and adventurous" modders.
No, that's not a typo. 35GB translates to over three hours if you have an ADSL2+ connection and live on top of your closest DSLAM. Whack on overhead, naturally dips in download speeds and the fact that most people are lucky to get 20Mb/s and it's going to take a fair bit longer to get your paws on this puppy.
The other fascinating fact is that building Megatextures is not what you'd describe as a speedy process. id's master coder John Carmack shared this tidbit on Twitter:
Doing significant work will require patience, because internally we use a 300 core renderfarm for megatexture creation.
— John Carmack (@ID_AA_Carmack) February 8, 2013
Obviously, the average modder won't be crafting Megatextures at dimensions to rival id, but it does make you wonder how your four or six-core CPU is going to fare when faced with such a daunting computational task.
I realise all this reads like a massive roast, but it's not. I just wanted to highlight the staggering amount of work that goes into triple-A titles these days — and not just from a coding or art standpoint. Kudos to the tireless programmers who come up with these tools, which I'd argue are just as critical to the development process as any texture, model or subroutine.