Bug 231108

Created attachment 439922 [details] broken rendering on iPhone 6 Overview: The GridMaterial shader from Babylon.js does not render correctly in Safari 15 on older iOS devices. Steps to Reproduce: 1) Open the following webpage on an iOS device with Safari 15: https://playground.babylonjs.com/#INI19S#6 Actual Results: Both the background plane and the ground plane are black. Expected Results: The background plane and the ground plane should have the same grid material as the sphere. This is the behavior in earlier versions of Safari and on other platforms (MacOS and Windows). Hardware: iPhone 6 running iOS 15 Additional Builds and Platforms: According to users, repros on (all iOS 15): iPhone SE iPad (6th generation) iPhone 7 iPad Pro On some devices it may render as fully white rather than fully black. Issue doesn't occur on MacOS, doesn't seem to occur on newer iPhones (but have not confirmed this personally). Additional Information: The post on our forum with users reporting the issue: https://forum.babylonjs.com/t/gridmaterial-not-shown-in-safari-on-ipad-after-update-to-ios-15-0/24210 The source for the fragment shader can be found here: https://github.com/BabylonJS/Babylon.js/blob/master/materialsLibrary/src/grid/grid.fragment.fx The issue appears in both WebGL 1 and 2. I have not yet been able to find the specific cause, but other shaders seem to work okay.