Drawing a poly to the terrain

My aim of this thread is to find a method to draw a poly to the terrain, any help is appreciated.
Also I am wondering if this is even possible to do since surface.DrawPoly only accepts X & Y co-ordinates.

Currently I am using 3D2D to draw a poly to the world, a problem with this is that 3D2D adds a 2D plane to draw to which means it will not be able to map to the terrain.

Any pointers in the right direction, examples or even a thought is welcome.

Thank you in advance.

GMod has a mesh library that can be used to draw 3D stuff like you want… but from what I’ve heard it’s pretty tricky to use

This is a great pointer, it looks hard but it also looks like its capable of what im asking.

I will keep the thread open in case someone would be kind enough to provide their findings but this is a definite win, thanks.