Decals Surface Shader example in the Built-In Render Pipeline

Important: The Built-In Render Pipeline is deprecated and will be made obsolete in a future release.
It remains supported, including bug fixes and maintenance, through the full Unity 6.7 LTS lifecycle.
For more information on migration, refer to Migrating from the Built-In Render Pipeline to the Universal Render Pipeline and Render pipeline feature comparison.

Decals are commonly used to add details to Materials at run time (for example, bullet impacts). They are especially useful in deferred rendering, because they alter the GBuffer before it is lit, therefore saving on performance.

In a typical scenario, Decals should be rendered after the opaque objects and should not be shadow casters, as seen in the ShaderLabUnity’s language for defining the structure of Shader objects. More info
See in Glossary “Tags” in the example below.

Shader "Example/Decal" {
  Properties {
    _MainTex ("Base (RGB)", 2D) = "white" {}
  }
  SubShader {
    Tags { "RenderType"="Opaque" "Queue"="Geometry+1" "ForceNoShadowCasting"="True" }
    LOD 200
    Offset -1, -1
    
    CGPROGRAM
    #pragma surface surf Lambert decal:blend
    
    sampler2D _MainTex;
    
    struct Input {
      float2 uv_MainTex;
    };
    
    void surf (Input IN, inout SurfaceOutput o) {
        half4 c = tex2D (_MainTex, IN.uv_MainTex);
        o.Albedo = c.rgb;
        o.Alpha = c.a;
      }
    ENDCG
    }
}

Final color modifier Surface Shader example in the Built-In Render Pipeline

Wrapped diffuse Surface Shader example in the Built-In Render Pipeline

Unity Manual

Decals Surface Shader example in the Built-In Render Pipeline