Generate 2D polygon collider from 3D mesh

Question

My game use 2d physic, but 3D graphics. The unity editor automatically generates a collider polygon using the sprite of the desired shape. If for example on a sprite a circle is drawn on a transparent background, then the generated collider polygon will be round. When the 2D scene mode is fixed, if you click on the 3d mesh model - it is outlined in orange (as can be seen in the screenshot), I want to make the polygon a collider polygon of the same shape as if it was a sprite. Tell me, please, how can I do this except to manually sketch the collider polygon? I need to algorithm working on at least simple examples as in the screenshot

Crosby

Answer 1

I was looking for this exact solution myself (All that dragging around polygon points was driving me insane).

Here’s an editor script I wrote that will match any PolygonCollider2D to the MeshFilter on a GameObject.

Just plop it into an Editor folder, highlight the GameObject, and click Update Polygon Colliders up in the Tools menu, or Ctrl/Cmd+T

Seems to work well with ProBuilder and in Prefab Edit Mode. I’m sure this can be greatly improved upon, feel free!

GIANT credit goes to @Hid for their EdgeHelper class Wouldn’t work nearly as well without it.

Unity Discussions – 1 Aug 15

Get Outer/Edge Vertices C#

Good Afternoon, I am trying to get all the outer/edge vertices from my mesh. I know I can get the y and x array but am having troubles just getting the outer vertices. using UnityEngine; using System.Collections; public class Shape : MonoBehaviour...

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System;
using UnityEditor.SceneManagement;
using System.Linq;

public static class SetPolygonCollider3D
{
    [MenuItem("Tools/Update Polygon Colliders %t", false, -1)]
    static void UpdatePolygonColliders()
    {
        Transform transform = Selection.activeTransform;
        if (transform == null)
        {
            Debug.LogWarning("No valid GameObject selected!");
            return;
        }

        EditorSceneManager.MarkSceneDirty(transform.gameObject.scene);

        MeshFilter[] meshFilters = transform.GetComponentsInChildren<MeshFilter>();

        foreach (MeshFilter meshFilter in meshFilters)
        {
            if (meshFilter.GetComponent<PolygonCollider2D>() != null)
            {
                UpdatePolygonCollider2D(meshFilter);
            }
        }
    }

    static void UpdatePolygonCollider2D(MeshFilter meshFilter)
    {
        if (meshFilter.sharedMesh == null)
        {
            Debug.LogWarning(meshFilter.gameObject.name + " has no Mesh set on its MeshFilter component!");
            return;
        }

        PolygonCollider2D polygonCollider2D = meshFilter.GetComponent<PolygonCollider2D>();
        polygonCollider2D.pathCount = 1;

        List<Vector3> vertices = new List<Vector3>();
        meshFilter.sharedMesh.GetVertices(vertices);

        var boundaryPath = EdgeHelpers.GetEdges(meshFilter.sharedMesh.triangles).FindBoundary().SortEdges();

        Vector3[] yourVectors = new Vector3[boundaryPath.Count];
        for (int i = 0; i < boundaryPath.Count; i++)
        {
            yourVectors _ = vertices[boundaryPath *.v1];
        }
        List<Vector2> newColliderVertices = new List<Vector2>();

        for (int i = 0; i < yourVectors.Length; i++)
        {
            newColliderVertices.Add(new Vector2(yourVectors_.x, yourVectors *.y));
        }

        Vector2[] newPoints = newColliderVertices.Distinct().ToArray();

        EditorUtility.SetDirty(polygonCollider2D);

        polygonCollider2D.SetPath(0, newPoints);
        Debug.Log(meshFilter.gameObject.name + " PolygonCollider2D updated.");
    }
}

public static class EdgeHelpers
{
    public struct Edge
    {
        public int v1;
        public int v2;
        public int triangleIndex;
        public Edge(int aV1, int aV2, int aIndex)
        {
            v1 = aV1;
            v2 = aV2;
            triangleIndex = aIndex;
        }
    }

    public static List<Edge> GetEdges(int[] aIndices)
    {
        List<Edge> result = new List<Edge>();
        for (int i = 0; i < aIndices.Length; i += 3)
        {
            int v1 = aIndices *;
            int v2 = aIndices[i + 1];
            int v3 = aIndices[i + 2];
            result.Add(new Edge(v1, v2, i));
            result.Add(new Edge(v2, v3, i));
            result.Add(new Edge(v3, v1, i));
        }
        return result;
    }

    public static List<Edge> FindBoundary(this List<Edge> aEdges)
    {
        List<Edge> result = new List<Edge>(aEdges);
        for (int i = result.Count - 1; i > 0; i--)
        {
            for (int n = i - 1; n >= 0; n--)
            {
                if (result_.v1 == result[n].v2 && result *.v2 == result[n].v1)
                {
                    // shared edge so remove both
                    result.RemoveAt(i);
                    result.RemoveAt(n);
                    i--;
                    break;
                }
            }
        }
        return result;
    }
    public static List<Edge> SortEdges(this List<Edge> aEdges)
    {
        List<Edge> result = new List<Edge>(aEdges);
        for (int i = 0; i < result.Count - 2; i++)
        {
            Edge E = result *;
            for (int n = i + 1; n < result.Count; n++)
            {
                Edge a = result[n];
                if (E.v2 == a.v1)
                {
                    // in this case they are already in order so just continoue with the next one
                    if (n == i + 1)
                        break;
                    // if we found a match, swap them with the next one after "i"
                    result[n] = result[i + 1];
                    result[i + 1] = a;
                    break;
                }
            }
        }
        return result;
    }
}

Boundless

Worked Perfectly for me, thank you. Probably saved me about 5 hours of manually aligning polygon colliers.

– Adust

I'm working with unity's ProBuilder and I was wondering if the script is possible to create an outline for shapes like this. For easier shapes it works perfectly!! (Btw the view in the screenshots won't be the game view) @Hid or @Boundless ][1]

– Raveaux

i have tried to use this and although it does generate a polygon collider, it only seems to do so from the bottom of the mesh, instead of from the angle of the camera, do you know of any way to fix this?

– Misdoubt

Hey, it seems like the script thingy only got half of the script and the other half is just plain text, which makes it really hard to just ctrl+v it into unity, and adds a few characters that aren't supposed to be there. I'm still a beginner in unity so i don't know how to debug it, especially since it's my first time using editor scripts. could you pls help? thanks in advance

– Cottbus