Example of Particle System GPU instancing in a Surface Shader

Here is a complete working example of Surface ShaderA program that runs on the GPU. More info
See in Glossary using Particle SystemA component that simulates fluid entities such as liquids, clouds and flames by generating and animating large numbers of small 2D images in the scene. More info
See in Glossary GPU Instancing:

Shader "Instanced/ParticleMeshesSurface" {
    Properties {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        // And generate the shadow pass with instancing support
        #pragma surface surf Standard nolightmap nometa noforwardadd keepalpha fullforwardshadows addshadow vertex:vert
        // Enable instancing for this shader
        #pragma multi_compile_instancing
        #pragma instancing_options procedural:vertInstancingSetup
        #pragma exclude_renderers gles
        #include "UnityStandardParticleInstancing.cginc"
        sampler2D _MainTex;
        struct Input {
            float2 uv_MainTex;
            fixed4 vertexColor;
        };
        fixed4 _Color;
        half _Glossiness;
        half _Metallic;
        void vert (inout appdata_full v, out Input o)
        {
            UNITY_INITIALIZE_OUTPUT(Input, o);
            vertInstancingColor(o.vertexColor);
            vertInstancingUVs(v.texcoord, o.uv_MainTex);
        }

        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * IN.vertexColor * _Color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

There are a number of small differences to a regular Surface ShaderA streamlined way of writing shaders for the Built-in Render Pipeline. More info
See in Glossary in the above example, which make it work with particle instancing.

Firstly, you must add the following two lines to enable Procedural Instancing, and specify the built-in vertex setup function. This function lives in UnityStandardParticleInstancing.cginc, and loads the per-instance (per-particle) positional data:

        #pragma instancing_options procedural:vertInstancingSetup
        #include "UnityStandardParticleInstancing.cginc"

The other modification in the example is to the Vertex function, which has two extra lines that apply per-instance attributes, specifically, particle colors and Texture Sheet Animation texture coordinates:

            vertInstancingColor(o.vertexColor);
            vertInstancingUVs(v.texcoord, o.uv_MainTex);