Mesh Lines - Horizontal and Vertical Edges

[_Aka_]

Untested code, but even if it is bugged, you get the idea.
Add this code in the CGVMesh class, and then call public method where appropriate

Code:

public struct Edge
        {
            public Vector3 a;
            public Vector3 b;
            public Edge(Vector3 p1, Vector3 p2)
            {
                a = p1; b = p2;
            }
        }

        public IEnumerable<Edge> GetHorizontalAndVerticalLines()
        {
            var result = new List<Edge>();
            foreach (CGVSubMesh subMesh in SubMeshes)
            {
                for (var i = 0; i < subMesh.Triangles.Length; i++)
                {
                    int triangleStart = subMesh.Triangles[i];

                    TryAddEdge(Vertex[triangleStart + 0], Vertex[triangleStart + 1], result);
                    TryAddEdge(Vertex[triangleStart + 1], Vertex[triangleStart + 2], result);
                    TryAddEdge(Vertex[triangleStart + 2], Vertex[triangleStart + 0], result);
                }
            }

            return result;
        }

        private static void TryAddEdge(Vector3 position1, Vector3 position2, List<Edge> result)
        {
            var direction = position1 - position2;

            if (Vector3.Angle(direction, Vector3.up) < 0.01f || Vector3.Angle(direction, Vector3.right) < 0.01f)
            {
                result.Add(new Edge(position1, position2));
            }
        }