Get border edges of mesh - in winding order

Question

I have a triangulated mesh. Assume it looks like an bumpy surface. I want to be able to find all edges that fall on the surrounding border of the mesh. (forget about inner verti

Answer 1

Traversal Code (not efficient - needs to be tidied up, will get to that at some point) Please Note: I store each segment in the chain as 2 indices - rather than 1 as suggested by Darren. This is purely for my own implementation / rendering needs.

        // okay now lets sort the segments so that they make a chain.

        var sorted = new List();
        var visited = new Dictionary();

        var startIndex = edges[0];
        var nextIndex = edges[1];

        sorted.Add(startIndex);
        sorted.Add(nextIndex);

        visited[0] = true;
        visited[1] = true;

        while (nextIndex != startIndex)
        {
            for (int i = 0; i < edges.Count - 1; i += 2)
            {
                var j = i + 1;
                if (visited.ContainsKey(i) || visited.ContainsKey(j))
                    continue;

                var iIndex = edges[i];
                var jIndex = edges[j];

                if (iIndex == nextIndex)
                {
                    sorted.Add(nextIndex);
                    sorted.Add(jIndex);
                    nextIndex = jIndex;
                    visited[j] = true;
                    break;
                }
                else if (jIndex == nextIndex)
                {
                    sorted.Add(nextIndex);
                    sorted.Add(iIndex);
                    nextIndex = iIndex;
                    visited[i] = true;
                    break;
                }
            }
        }

        return sorted;