Resolved Cull Front or Back in ShaderGraph (URP)

Hi all,

Just wondering if there is an option somewhere to cull front or back faces in Unity ShaderGraph, I can't seem to find anything. I'm using URP, maybe it's not an option in there?

Thanks!
Pete

 

Were you able to figure this out?

 

No! Sadly I think it might be one of those things that's just not available. There's an option to have two sided, but I think that's about it. In the end I flipped the polys in Houdini before importing them into Unity.

 

You can setup this functionality with "Is Front Face" plus "Branch" node. Then depending what you want, set Albedo, Alpha, whatever, linked by the outcome of the branch node. But this requires a double sided material.

But if you can avoid it, you would just setup the face direction in your 3D modelling program.

 

It's also possible if you tweak the generated code:
https://www.codinblack.com/outline-effect-using-shader-graph-in-unity3d/

 

My solution was to reverse the normals of the object with a simple editor script:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. [ExecuteInEditMode]
6. public class ReverseNormals : MonoBehaviour
7. {
8.  
9.     void Start()
10.     {
11.         MeshFilter filter = GetComponent(typeof(MeshFilter)) as MeshFilter;
12.         if (filter != null)
13.         {
14.             Mesh mesh = filter.sharedMesh;
15.  
16.             Vector3[] normals = mesh.normals;
17.             for (int i = 0; i < normals.Length; i++)
18.                 normals[i] = -normals[i];
19.             mesh.normals = normals;
20.  
21.             for (int m = 0; m < mesh.subMeshCount; m++)
22.             {
23.                 int[] triangles = mesh.GetTriangles(m);
24.                 for (int i = 0; i < triangles.Length; i += 3)
25.                 {
26.                     int temp = triangles[i + 0];
27.                     triangles[i + 0] = triangles[i + 1];
28.                     triangles[i + 1] = temp;
29.                 }
30.                 mesh.SetTriangles(triangles, m);
31.             }
32.         }
33.     }
34. }
35.  

 

Thank you so much man !!! That was exactly what I was looking for !
After hours / days looking for how to achieve that using shader coding, render pipeline changes etc, the answer is finally as simple as your script ! I didn't thought about that method, doing it directly on the mesh.

 

I had a hard time figuring it out myself. I am glad it helped out

 

For implemented Cull Front without used Script, I used this graph.

 

I've had this issue with a Sprite Unlit shader in URP and I couldnt for the life of me figure out why one of my older shaders had no culling, but any new one I made did.

It turns out that if you switch the shader to a Lit shader, select Both on Render Faces, and then switch back to Sprite Lit, it retains the Cull setting.

This has been a headache for a very long time for me as a lot of assets I had I couldn't select in the scene view when they were flipped (so they were culled). Just noticed that doing this method disables the culling under the hood.

This is kind of a bug, but also not - because I would like this as an exposed setting, because it enables me to work in my scene. Here is the code diff on both shaders when one of them is Sprite Unlit without doing this little trick first. Left side is before the trick, right is after.

 

Necroing this but I have a solution to do this via C# script, I searched everywhere online and couldn't find an answer to this question with this thread being one of the top results. The solution is as simple as enabling Allow Material Override on the shader graph. You can then edit the render face per material in the now exposed Surface Options, or via C# script with these:

Code (CSharp):

1.         material.SetFloat("_Cull", (float)CullMode.Off);
2.         material.SetFloat("_Cull", (float)CullMode.Front);
3.         material.SetFloat("_Cull", (float)CullMode.Back);

 

Sorry, yes that's the way now and I made it seem you need C#. I was searching for a way to do this specifically in C# at runtime, and this thread was one of the first results so I posted here.

 

But at runtine is possible to change it? I want to change to Both or Front depending of situation.
I had try by code mat.SetFloat("_Cull", (float)CullMode.Off); but nops...

 

Are the properties exposed?

 

Yes

Yes, but the material doesnt change. The parament change to Both but material doesnt change. I thought that maybe is because is necessary to active some part of the sahder like EnableKeyword...