Spline Package in Unity:

The spline can be used in camera movement/ AI or game object movement path/ trace of VFX/ mesh generate

Mesh generates in unity:

Generating mesh in unity just using scripts is about drawing out several planes and putting them together instead generate as a cube object. 

This requires: 

Vertex position = Red Dots 

Triangle Indices = Vertex numbers’ order to form triangles in a square (which will be (0, 3, 1) and (1, 3, 2) 

Normal Vector = Vector direction to stretch the plane 

UV Coordinate = Texture render vector