To ensure each copied character in Unity has its own material when using Spine, you can use the MaterialPropertyBlock or create unique material instances for each character. Here are the steps to achieve this:

1. Using MaterialPropertyBlock:
   This method allows you to change material properties for individual instances without creating new material instances. Here's an example of how to use it:

      using UnityEngine;
   
      public class ChangeMaterialProperties : MonoBehaviour {
          private MaterialPropertyBlock propertyBlock;
          private Renderer renderer;
   
          void Start() {
              renderer = GetComponent<Renderer>();
              propertyBlock = new MaterialPropertyBlock();
          }
   
          void Update() {
              propertyBlock.SetColor("_Color", Color.red); // Change the color property
              renderer.SetPropertyBlock(propertyBlock);
          }
      }

2. Creating Unique Material Instances:
   If you need to create unique material instances for each character, you can duplicate the material for each instance. Here’s how you can do it:

      using UnityEngine;
   
      public class DuplicateMaterial : MonoBehaviour {
          private Renderer renderer;
   
          void Start() {
              renderer = GetComponent<Renderer>();
              renderer.material = new Material(renderer.material); // Create a new instance of the material
          }
   
          void Update() {
              renderer.material.color = Color.red; // Change the color property
          }
      }

3. Using Spine's CustomMaterialOverride:
   Spine provides a way to override materials per instance. You can use the SkeletonRendererCustomMaterials component to assign custom materials. Here’s an example:

      using Spine.Unity;
   
      public class CustomMaterialOverrideExample : MonoBehaviour {
          public Material customMaterial;
          private SkeletonRendererCustomMaterials customMaterials;
   
          void Start() {
              customMaterials = GetComponent<SkeletonRendererCustomMaterials>();
              customMaterials.customMaterialOverrides.Add(new SkeletonRendererCustomMaterials.SlotMaterialOverride {
                  slotName = "slotName", // Replace with your slot name
                  material = customMaterial
              });
          }
      }

For more detailed information, you can refer to the Changing Materials Per Instance section in the spine-unity documentation.

TaeWoong I tried this method and it didn't work

What did you try, and what exactly did "not work"? What was your expected result and what did you receive instead?

TaeWoong Before running the game, the same custom slot material was inserted, and when I ran the game and inserted another material into the custom slot material, I found that it had individual materials.

I'm afraid I don't understand what you mean by the above. Please always describe precisely what materials you assigned where, "materials were assigned" is too ambiguous.

Regarding "I found that it had individual materials.": If you override the material at one slot only, then the material of this slot is one material, and in addition to the material of the other slot that makes two.

If you don't want only a single slot being affected and instead replace the material at all slots: you set the Custom Slot Material of the Body slot. As the name suggests, it replaces the material for a single slot. If you want to replace a material entirely, you need to use the Custom Material Overrides below Custom Slot Materials instead.

@TaeWoong Glad to hear you've figured it out, thanks for letting us know.