Using a written shader with shader_type canvas_item;, is it possible to draw polygons without mesh data/spatial nodes?

:information_source: Attention Topic was automatically imported from the old Question2Answer platform.
:bust_in_silhouette: Asked By Noddy

I’m trying to see if I can truly do 2.5 game engine stuff in Godot without the use of any true 3D functions/nodes. I have an idea about how to use Node2D stuff to create “sector” information and I can already create a basic “FPS” controller(since this “First” person controller is really a third person controller on a 2D node). So what I currently need to know, is how to create a shader that can draw polys(dumb, raster ones are fine by me) relative to the player character, sort of like projections of 2D map elements like the way Wolf3D and Doom used sector information. But I don’t know the best method for drawing polys in Godot Shaders(especially for canvas_item). Any help on where to find this info or any samples would be greatly appreciated.