Polygon.Vertex C# (CSharp) Method

    public Vector3 Vertex(int i)
    {
        return vertices[i];
    }

    // Join two polygons (assuming that they are adjacent and share an edge)
    public Polygon Join(Polygon other)
    {
        int thisEdgeId  = -1;
        int otherEdgeId = -1;

        for (int i = 0; i < Length() && thisEdgeId == -1; i++)
        {
            Vector3 thisFrom = Vertex(i);
            Vector3 thisTo   = Vertex((i + 1) % Length());
            for (int j = 0; j < other.Length(); j++)
            {
                Vector3 otherFrom = other.Vertex(j);
                Vector3 otherTo   = other.Vertex((j + 1) % other.Length());
                if ((thisFrom - otherTo).sqrMagnitude < 0.001f && (thisTo - otherFrom).sqrMagnitude < 0.001f)
                {
                    thisEdgeId  = i;
                    otherEdgeId = j;
                    break;
                }
            }
        }
        if (thisEdgeId == -1)
        {
            return(null);
        }
        Polygon res = new Polygon();

        // add current points
        for (int i = 0; i < Length(); i++)
        {
            res.vertices.Add(vertices[(i + thisEdgeId + 1) % Length()]);
        }
        otherEdgeId = otherEdgeId + 2;     // skip current since this equals the last vertex of res
        // add vertices from other
        for (int i = 0; i < other.Length() - 2; i++)
        {
            res.vertices.Add(other.vertices[(i + otherEdgeId) % other.Length()]);
        }

        // remove any edge (where two edges share endpoints but has different directions
        for (int i = 0; i < res.Length(); i++)
        {
            var  thisVert     = res.Vertex(i);
            var  nextNextVert = res.Vertex((i + 2) % res.Length());
            bool almostEqual  = (thisVert - nextNextVert).sqrMagnitude < 0.001f;
            if (almostEqual)
            {
                var vects = new int[] { (i + 1) % res.Length(), i };
                System.Array.Sort(vects);
                res.vertices.RemoveRange(vects[1], 1);
                res.vertices.RemoveRange(vects[0], 1);
                i = i + 2;
            }
        }

        return(res);
    }