Tim Sweeney is at it again, but this time with an editorial with his view on graphics technology (accelerators, engines, etc...) over the past couple of years. It's an interesting read, check it out.

When a company like Epic or id Software builds a 3D engine, we do it with the expectation of it powering games that sell a few million copies, between our games and licensee projects.  We make money from each one, and that realization drives investment in making more and better tools.  This gives our engines a price, performance, and feature advantage over "in-house" engines made specifically for one game, and over less-capable engines designed for niche markets.  We amortize our R&D investment over ~10X more units sold.  This licensing model has already proven successful with mainstream game developers, but now it's starting to overflow into non-game markets too.  We have this great 3D engine, why not use it for your architectural walkthrough?