The issue you're experiencing with MaterialPropertyBlock in Unity 6 might be related to changes in how Unity handles material properties or potential bugs introduced in the new version. There have been reports of issues when using MaterialPropertyBlock with Unity 6, particularly when properties are not initialized correctly, leading to unexpected behavior such as disappearing characters. This has been noted in the context of using MaterialPropertyBlock with Spine animations, where uninitialized data can cause problems. It is recommended to ensure that all properties are correctly initialized and to check if there are any updates or patches available for the spine-unity runtime that might address these issues. You can also try using the SkeletonAnimation.OnMeshAndMaterialsUpdated callback to manage material updates more reliably.

@Scoppex Sorry to hear you're having troubles. Which exact version of the spine-unity runtime are you using (name of the unitypackage, also listed in Assets/Spine/version.txt, or in the Package Manager window)?

Unfortunately I don't know what known issue Spinebot is referring to. I can't remember encountering this issue so far.

Did you perhaps switch from Build-In Render Pipeline to URP when switching to Unity 6?
Do you see any errors in the console?
Are you having multiple submeshes (multiple Materials) perhaps? Then you would need to call targetRenderer.SetPropertyBlock(propertyBlock, submeshIndex).

@Scoppex If you can create a minimal Unity project which still shows this issue (with only the character and a script setting the custom material), you can send us a zip file to contact@esotericsoftware.com (briefly mentioning this forum thread so that we know the context). Also be sure to not include the very large generated Library directory in the package. Then we can have a look at what's going wrong.

Thanks for sending the reproduction project. We'll get back to you here on the forum once we've figured out what's going wrong.

@Scoppex The problem seems to be that you're using MaterialPropertyBlock with Universal RP, which does not seem to be supported with Unity 6. When assigning any URP Material to a Cube (or Sprite), it does not display anything anymore when assigning an empty MaterialPropertyBlock:

propertyBlock = new MaterialPropertyBlock();
targetRenderer.GetPropertyBlock(propertyBlock);
targetRenderer.SetPropertyBlock(propertyBlock);

So I'm afraid this is unrelated to spine-unity and a new Unity 6 limitation in general.

Scoppex Although I admit I tried assigning it to a sprite and then it worked. I only had a problem with the spine object.

That's interesting to hear. After trying the same again I noticed that the Sprite indeed remained unchanged (did not disappear) after assigning the MaterialPropertyBlock, so remained working. I might have done something wrong with my earlier testing yesterday.

In general the MaterialPropertyBlock documentation states though:

Note that this is not compatible with SRP Batcher. Using this in the Universal Render Pipeline (URP), High Definition Render Pipeline (HDRP) or a custom render pipeline based on the Scriptable Render Pipeline (SRP) will likely result in a drop in performance.

What's interesting is that it works without issues on a MeshRenderer with raptor_Material which is included in the Spine URP Shaders samples, using Spine URP 2D shaders. It seems to just occur with shader graph materials and materials using Unity's own Universal Render Pipeline/2D/Sprite-* shaders.

Scoppex Is there a workaround to make it work?

Unfortunately I know of no magic settings yet to tick which make it work without issues. Disabling SRP Batching for example would have looked promising, but made your ShaderGraph materials not display already before assigning a MaterialPropertyBlock.

As options I see:

• 1) Writing a shader instead of using ShaderGraph.
• 2) Finding other means to make MaterialPropertyBlock work, e.g. making disabled SRP Batcher work with your ShaderGraph material.
• 3) Using alternatives to MaterialPropertyBlock.

An alternative to MaterialPropertyBlock would be managing and assigning a Material instance yourself. Assigning at a SkeletonRenderer could be done via SkeletonGraphic.CustomMaterialOverride or assigning them manually in the SkeletonRenderer.OnMeshAndMaterialsUpdated callback (see the docs here).

Scoppex However, I have a problem here. I can assign material:
skeletonAnimation.CustomMaterialOverride[originalMaterial] = materialInstance;

But when I try to change its values. They do not update on my character when I use:
materialInstance.SetFloat(propertyName, value);

We could not reproduce any issue with that, it worked on our end without any problems. Did you create the Material instance like this:

if (materialInstance == null)
    materialInstance = new Material(replacementMaterial);

Are you sure that the override is at all replacing the material, or whether perhaps the originalMaterial is set to the wrong material, never replacing anything?

Scoppex That's something completely different.
See the FAQ section here, under "Why do individual parts of my skeleton show through during alpha fadeout?"

Also see the documentation here:
https://esotericsoftware.com/spine-unity-rendering#Fading-a-Skeleton-In-or-Out
And check out the example scene RenderTexture FadeOut Transparency.

Scoppex But what about my previous question.

Please scroll one posting upwards for the reply
https://esotericsoftware.com/forum/d/28167-unity-6-and-custom-material-bug/16