Visualize mesh normals in Unity3D

README.md

Visualize the normals of a mesh

It's meant to be simple and easy to use, and therefore it has been made as a custom editor of MeshFilter. It needs no preparations.

How to use

Drop the file in an Editor folder.

Updates

• store the normals length i editor prefs
• adjust the normals length in the mesh filter inspector

NormalsVisualizer.cs

using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(MeshFilter))]
public class NormalsVisualizer : Editor {

    private const string     EDITOR_PREF_KEY = "_normals_length";
    private       Mesh       mesh;
    private       MeshFilter mf;
    private       Vector3[]  verts;
    private       Vector3[]  normals;
    private       float      normalsLength = 1f;

    private void OnEnable() {
        mf   = target as MeshFilter;
        if (mf != null) {
            mesh = mf.sharedMesh;
        }
        normalsLength = EditorPrefs.GetFloat(EDITOR_PREF_KEY);
    }

    private void OnSceneGUI() {
        if (mesh == null) {
            return;
        }

        Handles.matrix = mf.transform.localToWorldMatrix;
        Handles.color = Color.yellow;
        verts = mesh.vertices;
        normals = mesh.normals;
        int len = mesh.vertexCount;
        
        for (int i = 0; i < len; i++) {
            Handles.DrawLine(verts[i], verts[i] + normals[i] * normalsLength);
        }
    }

    public override void OnInspectorGUI() {
        base.OnInspectorGUI();
        EditorGUI.BeginChangeCheck();
        normalsLength = EditorGUILayout.FloatField("Normals length", normalsLength);
        if (EditorGUI.EndChangeCheck()) {
            EditorPrefs.SetFloat(EDITOR_PREF_KEY, normalsLength);
        }
    }
}

You've probably noticed this script creates massive slowdown on complex objects. This is for two reasons:

1. You only need to set the Handles matrix and colour once.
2. (much more serious): accessing mesh.vertices creates a copy of the entire vertex array. Same for accessing mesh.normals. Since you are accessing mesh.vertices twice and mesh.normals once for every vertex, you're forcing Unity to allocate and free up hundreds or thousands (or hundreds OF thousands) of vertex buffers every frame.

All you need to do is move the handles.matrix and colour lines outside the loop, and cache mesh.vertices and mesh.normals in local arrays, too:

Vector3 verts = mesh.vertices;
Vector3 norms = mesh.normals;

for (int.....)
{
Handles.DrawLine(verts[i],verts[i]+norms[i])
}

Thanks for pointing out the performance issues! One of the things I work with is performance optimizations, so it was rather embarrassing seeing this script again. I fully agree with you, and will update the gist. Thanks!

I just dropped the script in an Editor folder and I cannot see anything. Dropped a Cube in the Scene, select it or not, what should I see? In the inspector I see the "MeshFilter" with the Mesh field, and nothing else. I am on 2020.3

Hi @fakkoweb. I just tried the script in 2021.2.10 and it worked like expected. I tested with the default cube. I'm not quite sure why it doesn't work on your end. You should see yellow lines drawn along the normals of the mesh, in the scene view.

@mandarinx Thanks for this handy tool!
@fakkoweb I just used the script in 2019.4.14f1 and it workes for me. In the Mesh Filter component there's a new attribute called "Normals length", which is set to 0 by default. When I increase it, yellow lines appear, like mandarinx described.
It doesn't work when multiple meshes are selected.

@mandarinx works great! I don't have anough time to fork this, but i think you should add a boolean property like "Show Normals", so you can avoid computations in OnSceneGUI and just return from it. Without it unity starts lagging heavily when large mesh is selected even when you don't need to see normals and set Normal Length to 0.
Or maybe just return from OnSceneGUI when NormalLength == 0.
But i think my option is more logical, so that you don't need to fiddle with normals lenghts just to show it or hide.
Something like this should work

using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(MeshFilter))]
public class NormalsVisualizer : Editor {

    private const string     EDITOR_PREF_KEY = "_normals_length";
    private const string     EDITOR_PREF_BOOL = "_show_normals";
    private       Mesh       mesh;
    private       MeshFilter mf;
    private       Vector3[]  verts;
    private       Vector3[]  normals;
    private       float      normalsLength = 1f;
    private       bool       showNormals = false;

    private void OnEnable() {
        mf   = target as MeshFilter;
        if (mf != null) {
            mesh = mf.sharedMesh;
        }
        normalsLength = EditorPrefs.GetFloat(EDITOR_PREF_KEY);
        showNormals = EditorPrefs.GetBool(EDITOR_PREF_BOOL);
    }

    private void OnSceneGUI() {
        if (mesh == null || !showNormals) {
            return;
        }

        Handles.matrix = mf.transform.localToWorldMatrix;
        Handles.color = Color.yellow;
        verts = mesh.vertices;
        normals = mesh.normals;
        int len = mesh.vertexCount;
        
        for (int i = 0; i < len; i++) {
            Handles.DrawLine(verts[i], verts[i] + normals[i] * normalsLength);
        }
    }

    public override void OnInspectorGUI() {
        base.OnInspectorGUI();
        EditorGUI.BeginChangeCheck();
        showNormals = EditorGUILayout.Toggle("Show normals", showNormals);
        normalsLength = EditorGUILayout.FloatField("Normals length", normalsLength);
        if (EditorGUI.EndChangeCheck()) {
            EditorPrefs.SetBool(EDITOR_PREF_BOOL, showNormals);
            EditorPrefs.SetFloat(EDITOR_PREF_KEY, normalsLength);
        }
    }
}

I am on 2020.3.3f1 LTS. I have dropped this into an editor folder and I see nothing.
This is really a very important addon since this is missing in Unity. Excuse me?
I have been dropping tech upgrade bombs on Unity for years.
The last one was the suggestion for 'Local' in the objects transform area of the inspector window.
They finally did it in 2020.3.
This normals should be in Unity by default too.
Please help me get this to work. Thank you.
in assets/projectwork/editor folder

using UnityEditor;
using UnityEngine;

public class DebugTool_ShowNormal : MonoBehaviour
{
    public bool isShowNormal;
    public Color color = Color.yellow;
    public float normalsLength = 1f;

    private void OnDrawGizmosSelected()
    {
        if (!isShowNormal) return;

        if (!TryGetComponent<MeshFilter>(out var meshFilter)) return;

        var mesh = meshFilter.mesh;
        if (mesh == null) return;

        var defaultColor = Handles.color;
        Handles.matrix = transform.localToWorldMatrix;
        Handles.color = color;
        var verts = mesh.vertices;
        var normals = mesh.normals;
        int len = mesh.vertexCount;

        for (int i = 0; i < len; i++)
        {
            Handles.DrawLine(verts[i], verts[i] + normals[i] * normalsLength);
        }

        Handles.color = defaultColor;
    }
}

Thanks for sharing,
If someone is like me, just need to debug the Normal information in the short term,can use my code.
The principle is the same

Thanks for sharing - this was just what I needed to sort out a niggly bug!

Warning ... code can pose problems on large meshes ...

Sorry ... the code works but .. I used it on a large mesh and it crashed Unity. I lost about a day's worth of coding.  The problem however is not in code per se but in Unity, or rather both.  It will not work on large meshes. I am not completely sure why Unity crashed but I am working on a custom mesh with a lot of vertices, about 350,000.  As someone pointed out above there should be some way to limit the updating for large meshes.  Also, if the length of the normal in the inspector is set to zero, to hide the normal, then when it is set back to a non zero value the code will not work.  This has to do with some weird Unity editor updating behavior.  In addition there should be a way to turn the method off and on in an easy manner.

Does not work .. garbage code ...

first : it's working.

second: it's not garbage. even if it's not working.

third: maybe something else is garbage?

Sorry ... the code is okay .. got frustrated because it crashed Unity and I lost about a day's worth of coding. The problem is not in code but in Unity, or rather both. It will not work on large meshes. I am not completely sure why Unity crashed but I am working on a custom mesh with a lot of vertices. As someone pointed out in the code comments there should be some way to limit the updating for large meshes. Also, if the length is set to zero, to hide the normals, then when it is set back to a non zero value the code will not work. This has to do with some weird Unity editor updating behaviour. And there should be a way to turn the method off and on in an easy manner. I'll go back and get rid of my comment. If that's possible.

…

On Thu, Jan 11, 2024 at 4:53 PM Eran ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ Does not work .. garbage code ... first : it's working. second: it's not garbage. even if it's not working. third: maybe something else is garbage? — Reply to this email directly, view it on GitHub <https://gist.github.com/mandarinx/ed733369fbb2eea6c7fa9e3da65a0e17#gistcomment-4827373> or unsubscribe <https://github.com/notifications/unsubscribe-auth/BEPXBYR47EYMH4ASOKH3AATYOBUNRBFKMF2HI4TJMJ2XIZLTSKBKK5TBNR2WLJDUOJ2WLJDOMFWWLO3UNBZGKYLEL5YGC4TUNFRWS4DBNZ2F6YLDORUXM2LUPGBKK5TBNR2WLJDHNFZXJJDOMFWWLK3UNBZGKYLEL52HS4DFVRZXKYTKMVRXIX3UPFYGLK2HNFZXIQ3PNVWWK3TUUZ2G64DJMNZZDAVEOR4XAZNEM5UXG5FFOZQWY5LFVA2DANBRGY4TSNNHORZGSZ3HMVZKMY3SMVQXIZI> . You are receiving this email because you commented on the thread. Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub> .