An in-depth look into paper modeling from our good friend Angel David Guzmán / PixelOz, let this 227 page e-book be your guide into understanding the basics.
This is a free e-book that I just finished writing about how to design paper models (card models). It is based mainly on the freely available open source program Blender 3D and an illustration program of your choice but it teaches a lot of the most important fundamentals of 3D paper model design that have the tendency to give a wee bit of trouble to new designers. It is 227 pages long and has hundreds of full color illustrations to help you understand the concepts of the e-book better.
You can download a zip file that contains the e-book in PDF format by clicking Download at the top left of this web page, it also includes some Blender 3D files that can be used for practice and an additional unfolding script to the one that Blender already includes that has other important capabilities.
The e-book also talks about the many different types of software that can be used to accomplish the task.
The most important thing that I discovered while researching the subject was that where new designers had the most confusion was not in some complex thing of the design process but in some fundamental principles that were not well understood and I set out to explain them carefully to give designers a head start, so here it is, free help for those that are trying to learn this art of paper model design.
I hope that this e-book really helps to make you understand the subject better.
-Angel David Guzmán
UPDATE: Aug. 12, 2010 - version 1.1
Fundamentals of Paper Model Design Ebook [Download]