Board Thread:Questions and Answers/@comment-89.164.197.19-20141227191100/@comment-4750818-20141228133803

Circular windows would be just as hard to code. The windowframe would have to be square and opaque, but the centre would have to be round (which in itself is not that hard) and transparent (that's the hard part)...I see a lot of work required to make that a reality. In fact, I don't even know if Minecraft can handle some parts of a block being transparent and some parts of a block being opaque.

Glflegolas (admin) Send a PM 13:38, December 28, 2014 (UTC)