How can i output emission value to lightmap in vert/frag shader?

I can output emission value to baked lightmap with a surface shader. But how can i do it in vert/fragment shader.

I try to add a meta pass like this. Suppose to get red emission on the light map but nothing. Or did i miss something. Thanks.

Code (CSharp):

1. // ------------------------------------------------------------------
2.     // Extracts information for lightmapping, GI (emission, albedo, ...)
3.     // This pass it not used during regular rendering.
4.         Pass
5.         {
6.             Name "META"
7.             Tags {"LightMode"="Meta"}
8.             Cull Off
9.             CGPROGRAM
10.             #include"UnityStandardMeta.cginc"
11.             float4 frag_meta2 (v2f_meta i): SV_Target
12.             {
13.                 // we're interested in diffuse & specular colors,
14.                 // and surface roughness to produce final albedo.
15.            
16.                 FragmentCommonData data = UNITY_SETUP_BRDF_INPUT (i.uv);
17.                 UnityMetaInput o;
18.                 UNITY_INITIALIZE_OUTPUT(UnityMetaInput, o);
19.                 o.Albedo = fixed3(1,0,0);
20.                 o.Emission = fixed3(1,0,0);
21.                 return UnityMetaFragment(o);
22.             }
23.        
24.             #pragma vertex vert_meta
25.             #pragma fragment frag_meta2
26.             #pragma shader_feature _EMISSION
27.             #pragma shader_feature _METALLICGLOSSMAP
28.             #pragma shader_feature ___ _DETAIL_MULX2
29.             ENDCG
30.         }

 

I have working out the code. For those whose interesting to add a emission to their shader, here is the minimal setup.

Code (CSharp):

1.  
2. Pass
3. {
4.     Name "META"
5.     Tags {"LightMode"="Meta"}
6.     Cull Off
7.     CGPROGRAM
8.                
9.     #include "UnityStandardMeta.cginc"
10.     #pragma vertex vert_meta
11.     #pragma fragment frag_meta_custom
12.  
13.     fixed4 frag_meta_custom (v2f i) : SV_Target
14.     {
15.         // Colors              
16.         fixed4 col = fixed(1,0,0); // The emission color
17.  
18.         // Calculate emission
19.         UnityMetaInput metaIN;
20.           UNITY_INITIALIZE_OUTPUT(UnityMetaInput, metaIN);
21.           metaIN.Albedo = col.rgb;
22.           metaIN.Emission = col.rgb;
23.           return UnityMetaFragment(metaIN);
24.  
25.         return col;
26.     }
27.  
28.     ENDCG
29. }
30.