Normally when I start a Cesium discussion about Safari or iOS browsers, it’s with bad news; however I’m delighted to say that this time it’s great news!
Safari 10 (released yesterday for both Mac OSX and macOS Sierra) as well as the back-end used in iOS 10 for Safari/Chrome/Firefox appears to provide significant improvements for WebGL in general and Cesium specifically. I strongly encourage anyone looking to deploy to iPad, iPhones, and Safari desktop to upgrade to the latest Safari version.
For the first time I ever, I was able to run all Cesium unit tests to completion under desktop Safari and there were only 16 failures (some of which looked like problems with the test itself)
Also, they added support for the CSS “image-rendering” property which is already detected by Cesium and allows us to cleanly render at the OS preferred resolution (which should provide a significant boost on iOS and iPad).
There are still some wish list items, most notable EXT_frag_depth on iOS to enable geometry clamped to terrain; but this is a big win for Cesium and I’m hoping the days of Safari being a second-class WebGL implementation are finally over.