@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

Thanks for getting back to us, glad to hear you've figured it out.

Now my question is whether it would be better to set MaterialPropertyBlock and rewrite the shader from ShaderGraph or assign and use this new material?

Since the documentation lists that MaterialPropertyBlock is unsupported, it's rather risky to keep using MaterialPropertyBlock, as it might break in the future or on some platforms. I would at least recommend testing it on all target platforms if you should go with it.

There are no real downsides with managing your own instance Materials, once you've written the respective code. Batching should be broken anyway by either different MaterialPropertyBlocks or Material instances, so you lose nothing in this regard.

Scoppex I wonder in terms of efficiency and management (memory leaks with new materials?)?

You should not leak the material and only create it once per Skeleton and then re-use it (by having it constantly assigned via skeletonAnimation.CustomMaterialOverride[originalMaterial] = materialInstance;).

Scoppex In the future, I would also like to use this material to animate attachments separately. That is, for example, to animate the parameters of this shader separately for the sword, shield, etc. (e.g. it would have glowing animations when they were improved). What would be the best option?

You can set custom materials also per slot via SkeletonRenderer.CustomSlotMaterials.
You can check out the SkeletonRendererCustomMaterials utility component code as a reference.
The component is also documented here:
https://esotericsoftware.com/spine-unity-utility-components#SkeletonRendererCustomMaterials

Glad it helped, thanks for your kind words!