Some issues seem to have cropped up in the disk data container in yt-3.0. I made a disk object in a periodic simulation in the following way: http://paste.yt-project.org/show/5021/
I then made a project of the "cylindrical_z" field, which yielded the following: http://i.imgur.com/0XSv5Zs.png
For reference, the domain is ~45 Mpc in length on a side, so the sphere should be just the object at the bottom, extending a little less than halfway up. I don't know what that top part is about. My guess is that it's an issue with periodicity.
Secondly, I made a similar projection of the "cylindrical_r" field, which gave this: http://i.imgur.com/h8SEJp8.png
As you can see, it is not symmetric as one would expect. For reference, this is what I get from yt-2.x: http://i.imgur.com/O1xT9MI.png This is what I would expect.
Does anyone have any insight on this?