Create mesh section side?

Hello guys! I’m trying to create a 2D game using Procedural Mesh.

I have 3 vertices: 0 ; 0 , 100 ; 0 and 0 ; 100 (Z is not used).

The thing is, depending on the order of those vertices, the mesh section is faceing one side or another. I do not realize how this is calculated. Due this is a Procedural thing, I cannot be checking each mesh to fix this.

My question is, how can I get the mesh look up / down at will?

Thanks for all guys :smiley: