Example of Particle System Standard Shader custom vertex streams in the Built-In Render Pipeline

Here is an example of an animated flip-book ShaderA program that runs on the GPU. More info
See in Glossary. It uses the default inputs (Position, NormalThe direction perpendicular to the surface of a mesh, represented by a Vector. Unity uses normals to determine object orientation and apply shading. More info
See in Glossary, Color, UV), but also uses two additional streams for the second UV stream (UV2) and the flip-book frame information (AnimBlend).

Shader "Particles/Anim Alpha Blended" {
Properties {
    _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
    _MainTex ("Particle Texture", 2D) = "white" {}
    _InvFade ("Soft Particles Factor", Range(0.01,3.0)) = 1.0
}

Category {
    Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "PreviewType"="Plane" }
    Blend SrcAlpha OneMinusSrcAlpha
    ColorMask RGB
    Cull Off Lighting Off ZWrite Off

    SubShader {
        Pass {
        
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 2.0
            #pragma multi_compile_particles
            #pragma multi_compile_fog
            
            #include "UnityCG.cginc"

            sampler2D _MainTex;
            fixed4 _TintColor;
            
            struct appdata_t {
                float4 vertex : POSITION;
                fixed4 color : COLOR;
                float4 texcoords : TEXCOORD0;
                float texcoordBlend : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                float2 texcoord : TEXCOORD0;
                float2 texcoord2 : TEXCOORD1;
                fixed blend : TEXCOORD2;
                UNITY_FOG_COORDS(3)
                #ifdef SOFTPARTICLES_ON
                float4 projPos : TEXCOORD4;
                #endif
                UNITY_VERTEX_OUTPUT_STEREO
            };
            
            float4 _MainTex_ST;

            v2f vert (appdata_t v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o); 
                o.vertex = UnityObjectToClipPos(v.vertex);
                #ifdef SOFTPARTICLES_ON
                o.projPos = ComputeScreenPos (o.vertex);
                COMPUTE_EYEDEPTH(o.projPos.z);
                #endif
                o.color = v.color * _TintColor;
                o.texcoord = TRANSFORM_TEX(v.texcoords.xy,_MainTex);
                o.texcoord2 = TRANSFORM_TEX(v.texcoords.zw,_MainTex);
                o.blend = v.texcoordBlend;
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }

            sampler2D_float _CameraDepthTexture;
            float _InvFade;
            
            fixed4 frag (v2f i) : SV_Target
            {
                #ifdef SOFTPARTICLES_ON
                float sceneZ = LinearEyeDepth (SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture, UNITY_PROJ_COORD(i.projPos)));
                float partZ = i.projPos.z;
                float fade = saturate (_InvFade * (sceneZ-partZ));
                i.color.a *= fade;
                #endif
                
                fixed4 colA = tex2D(_MainTex, i.texcoord);
                fixed4 colB = tex2D(_MainTex, i.texcoord2);
                fixed4 col = 2.0f * i.color * lerp(colA, colB, i.blend);
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDHLSL 
        }
    }   
}
}