As for Luke. No affiance, but I really don't think is was a half round at all. Look how Vaders goes out from his neck, and down his sides, just forward of the sinter of his arms? That's a half round in my mind. If you look at the seans in Jabba's palace, then Luke has his hands folder in front of him. His cloke hangs down the front of him, almost meating in the front, leaving just enough of a gape to see his hands. This means it was either. a) a "3/4 round" cloak. (witch you could do with this pattern, with some mods) or b) A fare more complex pattern.
In other words, you couldn't pull Vader's cape closed, in the front, if you tried. I believe hat makes it a half round. Luke's, you could pull closed, if you really needed to. (though it may not be overly comfy if you did.)
None taken. I wish I had some better visual examples. Let me try to explain. The circumference of the cloak has nothing to do with how it closes on the neck, but more to do with the fullness around the body. Its kind of like a circle skirt. A half circle will have a little flair, but a full circle will start to fall in nice cascades around the figure. Dancers use sometimes 2-3 circle skirts where the outside circumference is a double or triple circle, but they somehow rangle that back into a single circle around the waistband. So the main difference in the Vader and Luke would be in how the neckline is cut. Let's just assume for an example that both capes are a half circle. That is to say, the outside circumference of each cape, when laid out flat on the floor, makes a half circle. Now the reason Lukes would close and Vader's not is because Luke's neckline is cut to his full neck measurement (actually a little bigger for comfort), and Vader's is only, say, half or 3/4 his neck measurement or perhaps gathered shorter. Both capes are still half circle, they just have different size necklines which terminate in the same circular arc as the outside(half circle, 3/4, etc.). So, in other words, for the half circle cloak, you just make the half circle at the neck as big as the area you want to cover. I'm not sure I'm explaining this very effectively without visuals. Does this make any sense at all?
Incidentally, they both look semicircular to me, though neither extremely so. I do think that Luke's has a little extra shaping in the shoulders though. You can do this on either a rectangular or circular cape by curving the side seams in at the shoulders. It does make things a little more complicated, but its an effective look.
I hope this post pushes this more towards a discussion than an argument.
So to further said discussion, here's a pic of the cloak I'm building. Its only about 95% finished. The picture quality is rough as I did it with my camera phone on the fly, but it gives you an idea of how this circular shape drapes around the body. The pattern is similar to what is in that link, with some alterations. As for the hood, I actually used the pattern in that tutorial as a base. I took a measuring tape and kind of draped it over the top of my head, as if it were the hood opening, and took that measurement (divided in half of course) and subbed it for the one on the front line of that pattern. I then scaled the other measurements up to fit. I think I extended it from 14" to 25", then lengthened it a bit because it was still very narrow.
