Thank you, I'd have couple of questions, but I know it is not a training section :)
I do not know so much about shader-magic; but I can see that is used mainly to draw the world.
What would be the reasoable way to add decor items to the map, like 3D buildings? Adding simple 'billboard' trees seem to be easy
Viewing post in 3D Racer System for Game Maker Studio 2 comments
Exactly, the billboard shader is already in there, so you would need to make non-moving objects and draw them through that shader, then place them. Make sure to check their depth values and such so that they appear on the same height as the vehicles :)
As for 3D buildings, you could create a vertex buffer for them, simple cubes stacked or something, and give them a texture. Look up DragoniteSpam tutorials on youtube, it will help a bunch!