Find edge/surface/ledge of mesh

Hello, I’ve been messing around with my character & i need to find out a way to detect if there’s an edge/surface/ledge so the character can grab on to it.

Take the image below for example

I would like to detect the areas that are lined red & that are an edge/surface using C# so the character can grab on to it.

Any help would be appreciated, thanks!

  • Jabez

Since the mesh is going to be dynamic, I suggest detecting the edge on the fly with casts. See the following picture:

You do a sphere cast (or horizontal raycast alternatively) above the character to detect if there is no vertical surface to climb to. You do a vertical raycast above and forward to detect if it is an actual edge. I used this technique successfully for a similar problem.

This approach does assume that you are generating/updating a collider mesh that matches the rendered mesh, or a proxy for that mesh (e.g. set of box colliders). If you have control over the colliders you might also want to separate the vertical and horizontal ones and tagged them differently for more specific checks.

So I have been trying to do something with this all day long. And I managed to get the quad that the player hits, get the top edge of it and check if it is climable. I think it only works with perfect quads, and its not very good at all, but it works. So its far from perfect but its a good base for you to start building on!

using UnityEngine;
using System.Collections;
//using System.Collections.Generic;
//using System.Threading;

//TODO Clean up stuff. Fix bug and tweak stuff. Optimize stuff. Animation support. Add climbing support. Make usable for non-perfect quads. Find all edges within reach instead of just the closest.
//Made in a day by Imre Angelo aka Lahzar @ the unity forums - Enjoy!
public class RunFree3o : MonoBehaviour {
		public float reach = 3;	//TODO Check from players arms, legs etc
private Vector3[] quad;
private Vector3[] top;

void Start()	{
	quad = new Vector3[4];

void Update()	{
	if(top[0] != new Vector3())
		Debug.DrawLine(top[0], top[1],, 1);

void OnControllerColliderHit(ControllerColliderHit col)	{
	RaycastHit hit;
	Debug.DrawRay(col.point, col.moveDirection,, 1);
	if(Physics.Raycast(transform.position, col.moveDirection, out hit, 0.5f))	{
		if(hit.normal.y == transform.position.y-(GetComponent<CharacterController>().height/2))

		MeshCollider meshCollider = hit.collider as MeshCollider;
		if (meshCollider == null || meshCollider.sharedMesh == null)
		Mesh mesh = meshCollider.sharedMesh;
		Vector3[] vertices = mesh.vertices;
		int[] triangles = mesh.triangles;
		Transform hitTransform = hit.collider.transform;

		StartCoroutine(CoroutineThing(mesh, hitTransform, vertices, triangles, hit.triangleIndex));

IEnumerator CoroutineThing(Mesh mesh, Transform hitTransform, Vector3[] vertices, int[] triangles, int triangleIndex)	{
	#region Get hit triangle
	Vector3 p0 = vertices[triangles[triangleIndex * 3 + 0]];
	Vector3 p1 = vertices[triangles[triangleIndex * 3 + 1]];
	Vector3 p2 = vertices[triangles[triangleIndex * 3 + 2]];
	p0 = hitTransform.TransformPoint(p0);
	p1 = hitTransform.TransformPoint(p1);
	p2 = hitTransform.TransformPoint(p2);

	Debug.DrawLine(p0, p1,, 4);
	Debug.DrawLine(p1, p2,, 4);
	Debug.DrawLine(p2, p0,, 4);

	#region Get last triangle
	Vector3 p3 = new Vector3();
	for(int i = 10; i > -10; i--)	{
		Vector3 p4 = new Vector3();
		if(vertices[triangles[triangleIndex * 3 + i]] == null)

		try {
			p4 = hitTransform.TransformPoint(vertices[triangles[triangleIndex * 3 + i]]);
		} catch (System.Exception ex)	{
			ex.Source = "ignore";

		if(p4 != p0 && p4 != p1 && p4 != p2)	{

			int ex = 0, wai = 0, zed = 0;
			if(Mathf.FloorToInt(p4.x) == Mathf.FloorToInt(p0.x))	{	ex++;	}
			if(Mathf.FloorToInt(p4.y) == Mathf.FloorToInt(p0.y))	{	wai++;	}
			if(Mathf.FloorToInt(p4.z) == Mathf.FloorToInt(p0.z))	{	zed++;	}
			if(Mathf.FloorToInt(p4.x) == Mathf.FloorToInt(p1.x))	{	ex++;	}
			if(Mathf.FloorToInt(p4.y) == Mathf.FloorToInt(p1.y))	{	wai++;	}
			if(Mathf.FloorToInt(p4.z) == Mathf.FloorToInt(p1.z))	{	zed++;	}
			if(Mathf.FloorToInt(p4.x) == Mathf.FloorToInt(p2.x))	{	ex++;	}
			if(Mathf.FloorToInt(p4.y) == Mathf.FloorToInt(p2.y))	{	wai++;	}
			if(Mathf.FloorToInt(p4.z) == Mathf.FloorToInt(p2.z))	{	zed++;	}
			if(ex+wai+zed == 5)	{
				if(wai == 1)	{
					p3 = p4;
	Debug.DrawLine(p0, p3,, 4);
	Debug.DrawLine(p1, p3,, 4);
	Debug.DrawLine(p2, p3,, 4);

	if(p3 != new Vector3())	{
		quad = new Vector3[4];
		quad[3] = p3;

	quad[0] = p0;
	quad[1] = p1;
	quad[2] = p2;

	yield return null;

IEnumerator CheckMoves()	{
	top = new Vector3[2];
	foreach(Vector3 v in quad)	{
		if(v == new Vector3())

		if(Mathf.FloorToInt(v.y) == Mathf.FloorToInt(top[0].y) && v.y > top[1].y)	{
			top[1] = top[0];
			top[0] = v;
		} else if(v.y > top[0].y)	{
			top[1] = top[0];
			top[0] = v;

	if(Vector3.Distance(transform.position, (top[0]+top[1])/2) <= reach)	{  //This code block doesn't always work!
		if(!Physics.CheckCapsule((top[0]+top[1])/2, (top[0]+top[1])/2+Vector3.up*2, 0.5f) && !Physics.Raycast((top[0]+top[1])/2+Vector3.up*2, Vector3.down, 1.95f))	{
			if(Physics.Raycast((top[0]+top[1])/2+Vector3.up*2+transform.forward/2, Vector3.down, 2.1f))	{
				transform.position = (top[0]+top[1])/2+Vector3.up*2;

	yield return null;

First it gets the triangle that the players controllercollider hits. Then it Tries to figure out which vertex is the needed vertex to find the adjacent triangle and thus the whole quad. Now that its sure there is a level top edge, it finds the highest edge. Then it checks if the standard unity FPS controller can fit ontop of said edge! That last part is buggy but it works okay. Try it for yourself!

Put invisible trigger colliders