We wanted the app to work on an iPhone and that required the use of Apple Metal code. This could of course be ported to a desktop but we're not sure there would be much interest in that?
Really cool app btw!
I have once seen a video of Kip Thorne, explaining that the black hole visual effects of Interstellar were an actual physical simulation. I wouldn't have thought, that it was feasible to run on an iPhone.
As a physicist with a modest background in computing, I was also surprised by how powerful the iPhone GPU is. It can indeed lens the input from the camera at high resolution and in real time with high FPS.