How to add lightmap for this shader?

Hi,
how do I add lightmap for this shader?


// - Unlit

Shader "atsGrass-Unlit-Wind" {
Properties {
_MainTex ("Base (RGB) Alpha (A)", 2D) = "white" {}
_Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
}

SubShader {
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "LightMode"="ForwardBase"}
LOD 100
Cull Off
ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha


CGINCLUDE
#include "UnityCG.cginc"
sampler2D _MainTex;
half4 _MainTex_ST;

float4 _GrassWind; //is not defined in terrainengine.cginc

struct v2f {
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};

inline float4 AnimateGrass(float4 pos, float3 normal, float animParams)
{
// animParams stored in color
// animParams = primary factor = blue
// Primary bending
// Displace position
pos.xyz += animParams * _GrassWind.xyz * _GrassWind.w; // controlled by vertex color blue
return pos;
}



v2f vert (appdata_full v)
{
v2f o;
float4 windParams = float(v.color.b);
// call vertex animation
float4 mdlPos = AnimateGrass(v.vertex, v.normal, windParams);
o.pos = mul(UNITY_MATRIX_MVP,mdlPos);
o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}
ENDCG

Pass {
CGPROGRAM
#pragma debug
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest
fixed4 frag (v2f i) : COLOR
{
fixed4 tex = tex2D (_MainTex, i.uv);

fixed4 c;
c.rgb = tex.rgb;
c.a = tex.a;

return c;
}
ENDCG
}
}
}

 

Insert unity build-in support light map shader into your "frag" function.
Multiply sampled light map color with "tex.rgb" would be good.

 

Thank you very much for your answer !