I totally did not expect to have this done start to finish in one evening with Inkscape. Origami tutorials have suddenly become a lot easier than I anticipated, which is awesome since it'll probably let me document the rest of my designs before the summer's over. It's like the program reads my mind somehow.

Update: fuzzy edge issues fixed I hope (had exported to the wrong resolution).

Difficulty
I described this as intermediate rather than easy because of step 8. If you're familiar enough with sink folding to be able to fudge an open/partially closed sink fold to meet whatever inner structure you created with the angles chosen in previous steps, it should be easy enough (and if it's not, really, just mash the paper down as far as it needs to go and try to keep the previous folds intact...).

Alternative Steps
If you're really ambitious, the mane can be better defined using a sink fold rather than just bending it over a bit. I don't usually do the sink fold version unless I'm using really big paper. This can also allow for the ears to become pointier and better defined with an extra crimp.

Usage Policy
To me this design is not complicated, so I would expect that other people have happened across similar to nearly identical patterns. However, I did develop this myself and therefore hope that my choice of details is at least somewhat unique. If you follow this tutorial to create a horse/unicorn and wish to post the result as artwork either here or elsewhere, please credit the design you used to create the horse/unicorn.

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UPDATE (17-June-2009): HOOOLLLYYY COW! Woke up this morning and was completely confused by my message count until I saw one referencing the DD in one of the comments here. Took a few minutes and a cup of coffee for that to sink in all the way. Thanks so much everyone!!!

Here are some good videos about sink folds and other folds, which may help for those that get stumped in the first few steps of my design:
- Open sink (they call it a reverse sink for some reason, but it's the same thing)
- Open/closed sink
- More complex sinks
- Inside/outside reverse fold

Getting the back legs to look good is probably the hardest part of this design. If it doesn't come out right on the first try, small adjustments in the folds from steps 6-8 may be all that's needed to get the hind legs back in shape. Sometimes those can be adjusted without completely having to undo and redo everything. Also, this is intended to be a 3-D design, so the proportions can be modified somewhat as the model is shaped to be 3-D. So, if your models legs don't exactly match the diagrams (there's quite a lot of variation even in the models I've made!), try shaping to see if you still get the desired result. You can also do other modifications to thin the body or legs as you see fit. The silver unicorn pictured has one such modification made to the underside of the body.


UPDATE (19-June-2009): a video tutorial was requested, so I gave it my best shot for those that are having trouble: [link] . Please note though that it's the first video like that I've ever done, so I don't know if it shows things in enough detail. I was a bit worried about the webcam resolution, but that's the best I could get.