I am a graphic designer modelling a book so that I can map the book covers I've designed onto it for display in my portfolio. So, this book I'm modelling has to be very accurate in terms of measurements and proportions (don't want my designs warping). And realistic as well. So my question is how do I measure the length of the folded book jacket? It can't just be a box, because I want it to have warps and bends like a real book jacket folded over a book. So you can see what I'm talking about, here's what I have so far, with just a base red color for the jacket.
Basically, the height is obviously easy to get. But how do I get the width? (I have the unfolded book jacket image that I want mapped onto that book jacket that bends around). What is the easiest way to map this to make sure that there will be no stretching and that the width corresponds to the real image?