Want to display a 3D model on the iPhone: how to get started?

You should probably start with some simpler iphone apps/tutorials, just to get your footing on obj-c and xcode etc.

For that, I recommend the pragmatic programmer's iphone book, which has enough information to get started (I started with no knowledge of xcode, obj-c, iphone or mac and got to a working app fairly fast, using mainly this). However I should add that I come from a fairly good background in C/C++ and Java.

For your particular project, perhaps take a look at this answer which refers to an open source 3D app that you can look at and get tips from.

Once again, if I may plug my own work, I have written a post about the things I've learned from developing an OpenGL ES application on the iPhone. That application, Molecules (referred to by frankodwyer), is open source and I have a writeup on some of the other tricky issues I ran into while developing it. The application generates 3-D models and lets you rotate and scale them with your fingers, which sounds close to your needs. You can download the code, compile it, and run it on your desktop in a matter of a few minutes. If you join the iPhone Developer Program, you can install it on your device.

When it comes to object loading, Bill Dudney is working on a Wavefront OBJ loader for the iPhone that might be able to take in your Blender files, should they be exportable in that format. I haven't done much texture work on the iPhone yet, but it sounds like his example has that working now.

Overall, I find that learning by example and by jumping into development of some small, targeted applications (that you may never release) are what works for me. Try tweaking the examples listed above and see what happens. You should be able to read through the Objective-C code in those examples and start to get a feel for what they're doing.

Even though Hillegass's book (the third edition just came out and is up-to-date) focuses on the Mac, the Cocoa fundamentals he teaches are still relevant for the iPhone. The MVC design pattern serves you just as well on the iPhone as the Mac. I actually deviated from that pattern in a few places within Molecules, and I regret that decision because those sections of the application became a mess. The book is an easy read and well worth your time.