Changing material properties on one object changes all others

Question

I have a fadeout script to change the material properties when something blocks the screen. I want the objects to fade individually but when a new object fades, all the others also start the fade again or start fully faded out immediately.

The Docs say changing material properties using renderer.material creates a new instance of the material, but the behaviour I see points to them still being the same instance.

The material is a simple unlit ghader graph and here’s the Coroutine I use to fade the object:

IEnumerator TransitionTransparency ()
{
    _renderer.material = _transparentMat;
  
    float transition = 1;
    while (transition > 0) {
        _renderer.material.SetFloat("_Transition", transition);
  
        transition -= Time.deltaTime / _transitionTime;
        yield return null;
    }
  
    Destroy(_renderer.material);
    _renderer.material = _transparentMat;
      
    yield break;
}

Lodestar

Answer 1

I’d recommend Material Property Blocks. It is a class that you can set to almost every renderer and it will override the renderer’s shader properties.

For Instance, here is a script that I wrote for tweaking the _Fade property using DOTween.

using DG.Tweening;
using UnityEngine;
using UnityEngine.Events;
  
public class Interactable : MonoBehaviour, IRaycastEnter
{
    [SerializeField] protected MeshRenderer mR;
    protected MaterialPropertyBlock mPB;
    protected Vector3 StartScale;
  
    protected float tw = 0;
  
    protected virtual void Awake()
    {
        mPB = new MaterialPropertyBlock();
    }

     // This isn't the whole script but I think that would be enough to show how it works.
    public virtual void OnRaycastEnter()
    {
        if (!interactable) return;
  
        //throw new System.NotImplementedException();
        if (flashTW != null) flashTW.Kill();
        flashTW = DOTween.To(() => tw, x => tw = x, 1, .22f)
                .OnUpdate(() =>
                {
                    mR.transform.localScale = StartScale * (1 + (tw * scaleMultiplier));
                    // This is the Material Property Part, first you get the property block from the renderer.
                    mR.GetPropertyBlock(mPB);

                    //Then you tweak the values in the Material Property Block
                    mPB.SetFloat("_Fade", tw);

                    //Finally you set the property block of the renderer
                    mR.SetPropertyBlock(mPB);
                });
    }
}

Healthful

Thanks, Tried it out and this solution works even without setting the override. I rewrote my code to use DOTween in the meantime (forgot I had it in the project) and for a single property it seems simpler. I suppose the upside of using your solution (apart from being what unity is pushing towards, I guess) is that fewer draw calls are made, so it definitely has merit when many objects are changed. Anyways, thanks for pointing out a feature I was unaware of.

– Lodestar

Answer 2

So after trying out a few things I found the solution.
Leaving it here for anyone having a similar issue in the future.

The problem is with how shadergraph shaders handles non-exposed properties by default.
If you want to have a non-exposed property that can be changed for every material instance you have to enable “Override property declaration” and set “Shader Declaration” to “per material” in the property settings.

Lodestar

Answer 3

For anyone wondering what @Lodestar is talking about

As of Unity 2023.2, The "Override property declaration” is located here:

image1088×605 60.3 KB

For anyone wondering what I was making, It’s called a Toon / Cel shader which I’ve replicated from here

Whitelivered