iOS devices (iPhone, iPod Touch, iPad) are powered by 3D chips branded “PowerVR” from a company branded as “Imagination”.
If you want to develop 3D games/apps, you can do that using Apple’s free tools + SDK. But some of the good stuff – e.g. higher-res textures – you’ll need to dive into PowerVR specifics. This should *in theory* be very, very, very easy. But Imagination does not make it so :(.
All you really need is a few source files, but instead of putting them on their website to for you to download, Imagination has wrapped them up in a 1 gigabyte (broken) self-extractor. And it doesn’t work. It *really* doesn’t work. Read on for some of the joys of just how awful something as simple as a “unzip this file” program can get…
UPDATE: I realised after posting that I left out a very important point. Until this mess, I’d found Imagination’s tech guys to be friendly and helpful, and their tools to be useful and to work fine. They were always badly documented (e.g. very bad error handling, missing key facts like “a 64 megabyte texture requires 3 GIGABYTES of RAM to save”, etc – but they essentially “worked”). Maybe I just got lucky until now, but this installer seems a radical departure in terms of quality and testing. For anyone who’s *not* used the PowerVR stuff before, bear this in mind: IME, this experience is not normal. Also: use the forums – the support team seems pretty responsive.
TL;DR – if you want to load PVR textures on iOS, google for “PVR” and “iOS” and “copyright imagination” and find the header files and source that are embedded in a couple of open-source projects from a couple years back, before Imagination accidentally broke everything.