iOS and iPadOS still have some limitations in the number of lights and shaders one can use in WebGL projects.
Also, antialiasing can give some problems.
When using the Verge3D Outline feature, fine details don’t render smoothly on iOS devices and sometimes even look pixelated.
It seems to have something to do with iOS having troubles with SSAA antialiasing.
I found this post on the Epic Games forum. Also there it gives problems. https://forums.epicgames.com/udk/udk-development/ios-development/280332-how-to-enable-msaa-anti-aliasing-on-ios-for-ipad
For one of my projects where it was very bad, I could make a workaround but hopefully, it will be solved when iOS will support WebGL 2.0.
@illussimo, I wouldn’t hold my breath waiting for Apple to ship WebGL 2.0. Apple could have done this years ago, but choose not to do it. Apple has a history of poor support for open standard APIs. They have deprecated OpenGL and OpenCL on the desktop. They don’t support Vulkan. Apple has its own 3D low-level API called Metal. Based on what I have read, it seems that Apple wants to jump to WebGPU for 3D on the web. I would be happy to be wrong.