PolygonCollider2D Mesh Draw Scripts. These 3 scripts allow you to visualize a PolygonCollider2D as a mesh in the Unity game world. Can be used during Edit Mode also to permanently save the Mesh to the scene, but note the Start() method of PolygonDrawScript currently rebuilds the mesh when the game starts anyway. See: https://www.reddit.com/r/Uni…

PolygonDrawScript.cs

// Note this file goes in Assets/

using UnityEngine;
using System.Collections.Generic;

[RequireComponent(typeof(PolygonCollider2D), typeof(MeshFilter), typeof(MeshRenderer))] // require PolygonCollider2D, MeshFilter, and MeshRenderer
public class PolygonDrawScript : MonoBehaviour
{
    private PolygonCollider2D Poly
    {
        get { return _poly ?? (_poly = gameObject.GetComponent<PolygonCollider2D>()); }
    }
    private PolygonCollider2D _poly;

    private MeshFilter Filter
    {
        get { return _filter ?? (_filter = gameObject.GetComponent<MeshFilter>()); }
    }
    private MeshFilter _filter;

    private MeshRenderer Renderer
    {
        get { return _renderer ?? (_renderer = gameObject.GetComponent<MeshRenderer>()); }
    }
    private MeshRenderer _renderer;

    public void Start()
    {
        RebuildMesh();
    }

    public void RebuildMesh()
    {
        // Use the triangulator to get indices for creating triangles
        var tr = new Triangulator(Poly.points);
        var indices = tr.Triangulate();

        // Create the Vector3 vertices
        var vertices = new Vector3[Poly.points.Length];
        for (var i = 0; i < vertices.Length; i++)
        {
            vertices[i] = new Vector3(Poly.points[i].x, Poly.points[i].y, 0);
        }

        // Create the mesh
        var msh = new Mesh
        {
            vertices = vertices,
            triangles = indices
        };
        msh.RecalculateNormals();
        msh.RecalculateBounds();

        Filter.mesh = msh;
    }
}

PolygonDrawScriptInspector.cs

// Note this file goes in Assets/Editor/

using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(PolygonDrawScript))]
public class PolygonDrawScriptInspector : Editor
{
    public override void OnInspectorGUI()
    {
        DrawDefaultInspector();

        var myScript = (PolygonDrawScript)target;
        if (GUILayout.Button("Rebuild Polygon Mesh"))
        {
            myScript.RebuildMesh();
        }
    }
}

Triangulator.cs

// Note this file goes in Assets/

using System.Collections.Generic;
using UnityEngine;

// Taken from http://wiki.unity3d.com/index.php?title=Triangulator
public class Triangulator
{
    private List<Vector2> m_points = new List<Vector2>();

    public Triangulator(Vector2[] points)
    {
        m_points = new List<Vector2>(points);
    }

    public int[] Triangulate()
    {
        List<int> indices = new List<int>();

        int n = m_points.Count;
        if (n < 3)
            return indices.ToArray();

        int[] V = new int[n];
        if (Area() > 0)
        {
            for (int v = 0; v < n; v++)
                V[v] = v;
        }
        else
        {
            for (int v = 0; v < n; v++)
                V[v] = (n - 1) - v;
        }

        int nv = n;
        int count = 2 * nv;
        for (int m = 0, v = nv - 1; nv > 2;)
        {
            if ((count--) <= 0)
                return indices.ToArray();

            int u = v;
            if (nv <= u)
                u = 0;
            v = u + 1;
            if (nv <= v)
                v = 0;
            int w = v + 1;
            if (nv <= w)
                w = 0;

            if (Snip(u, v, w, nv, V))
            {
                int a, b, c, s, t;
                a = V[u];
                b = V[v];
                c = V[w];
                indices.Add(a);
                indices.Add(b);
                indices.Add(c);
                m++;
                for (s = v, t = v + 1; t < nv; s++, t++)
                    V[s] = V[t];
                nv--;
                count = 2 * nv;
            }
        }

        indices.Reverse();
        return indices.ToArray();
    }

    private float Area()
    {
        int n = m_points.Count;
        float A = 0.0f;
        for (int p = n - 1, q = 0; q < n; p = q++)
        {
            Vector2 pval = m_points[p];
            Vector2 qval = m_points[q];
            A += pval.x * qval.y - qval.x * pval.y;
        }
        return (A * 0.5f);
    }

    private bool Snip(int u, int v, int w, int n, int[] V)
    {
        int p;
        Vector2 A = m_points[V[u]];
        Vector2 B = m_points[V[v]];
        Vector2 C = m_points[V[w]];
        if (Mathf.Epsilon > (((B.x - A.x) * (C.y - A.y)) - ((B.y - A.y) * (C.x - A.x))))
            return false;
        for (p = 0; p < n; p++)
        {
            if ((p == u) || (p == v) || (p == w))
                continue;
            Vector2 P = m_points[V[p]];
            if (InsideTriangle(A, B, C, P))
                return false;
        }
        return true;
    }

    private bool InsideTriangle(Vector2 A, Vector2 B, Vector2 C, Vector2 P)
    {
        float ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
        float cCROSSap, bCROSScp, aCROSSbp;

        ax = C.x - B.x; ay = C.y - B.y;
        bx = A.x - C.x; by = A.y - C.y;
        cx = B.x - A.x; cy = B.y - A.y;
        apx = P.x - A.x; apy = P.y - A.y;
        bpx = P.x - B.x; bpy = P.y - B.y;
        cpx = P.x - C.x; cpy = P.y - C.y;

        aCROSSbp = ax * bpy - ay * bpx;
        cCROSSap = cx * apy - cy * apx;
        bCROSScp = bx * cpy - by * cpx;

        return ((aCROSSbp >= 0.0f) && (bCROSScp >= 0.0f) && (cCROSSap >= 0.0f));
    }
}