What is the Babylon way of elegantly writing per vertex shaders for WebGL 1.0 only browsers? Is there a higher level abstraction that maps to gl_VertexID in case of WebGL 2.0 and to a similar vertex identifier in WebGL 1.0?
No, there’s no such thing.
What you can do is creating a specific attribute that you pass to the vertex shader in which you put the vertex ids you want to use.
Thank you @Evgeni_Popov . Have a wonderful day.