WireframeRenderer.cs

// Simple shaderless Unity 5 Wireframe Renderer (can be used on top of materials)
// OJ2016
using System.Collections.Generic;
using UnityEngine;

// ReSharper disable once UnusedMember.Global
[RequireComponent( typeof( MeshFilter ) )]
public class WireframeRenderer: MonoBehaviour {
    private List<Vector3> RenderingQueue;

    private void InitializeOnDemand() {
        if ( RenderingQueue == null ) {

            var meshFilter = gameObject.GetComponent<MeshFilter>();
            if ( meshFilter == null ) {
                Debug.LogError( "No mesh detected at" + gameObject.name, gameObject );
                return;
            }
            var mesh = meshFilter.mesh;

            RenderingQueue = new List<Vector3>();
            foreach (var point in mesh.triangles) {
                RenderingQueue.Add( mesh.vertices[point] );
            }
        }
    }

    // ReSharper disable once UnusedMember.Global
    public void OnPreRender() {
        GL.wireframe = true;
    }

    // ReSharper disable once UnusedMember.Global
    public void OnRenderObject() {
        InitializeOnDemand();
        var color = Color.black;
        GL.MultMatrix( transform.localToWorldMatrix );
        GL.Begin( GL.LINES );
        GL.Color( color );

        for ( var i = 0; i < RenderingQueue.Count; i+=3 ) {
            var vertex1 = RenderingQueue[i];
            var vertex2 = RenderingQueue[i+1];
            var vertex3 = RenderingQueue[i+2];
            GL.Vertex3( vertex1.x, vertex1.y, vertex1.z );
            GL.Vertex3( vertex2.x, vertex2.y, vertex2.z );
            GL.Vertex3( vertex2.x, vertex2.y, vertex2.z );
            GL.Vertex3( vertex3.x, vertex3.y, vertex3.z );
            GL.Vertex3( vertex3.x, vertex3.y, vertex3.z );
            GL.Vertex3( vertex1.x, vertex1.y, vertex1.z );
        }
        GL.End();
    }

    // ReSharper disable once UnusedMember.Global
    public void OnPostRender() {
        GL.wireframe = false;
    }

}