Surface Shader - Calling Standard Lighting Function From Custom Lighting Function

I'm trying to create a special kind of light by putting special conditions into the light's cookie. If it's a certain kind of light, do my own calculation, otherwise, use the Standard lighting calculations.

I've created a Surface Shader using the "Create > Shader > Standard Surface Shader" Menu item from the project tab.

In the shader, I've created a custom lighting function:

Code (CSharp):

1.  
2. #pragma surface surf Custom
3. inline half4 LightingCustom(SurfaceOutput s, half3 lightDir, half atten)
4. {
5.     if (_LightColor0 or _LightTexture0 meets a condition)
6.     {
7.         //Do a custom lighting calculation
8.     }
9.     else
10.     {
11.          //Use the Standard lighting calculation(s)
12.     }
13. }

My question is, how do I call Unity's standard lighting calculations? Is it that simple? Would I be better off using a multi-compile statement and setting the conditions another way?


Edit: I should note, I would love to just modify DefaultResourcesExtra/Standard.shader, but I'm not sure where to even begin there. I only need a sub-set of the standard shader's input power (Normal Maps and Emission). So creating my own surface shader seemed like a simpler option.

 

Here you are.

Code (ShaderLab):

1. CGPROGRAM
2.  
3. #pragma surface surf Custom fullforwardshadows
4. #include "UnityPBSLighting.cginc"
5.  
6. // ...
7. // ...
8. // ...
9.  
10. inline half4 LightingCustom(SurfaceOutputStandard s, half3 lightDir, UnityGI gi)
11. {
12.     return LightingStandard(s, lightDir, gi);
13. }
14.  
15. inline void LightingCustom_GI(SurfaceOutputStandard s, UnityGIInput data, inout UnityGI gi)
16. {
17.     LightingStandard_GI(s, data, gi);
18. }
19.  
20. ENDCG
21.  

 

Thank you!

 

Apologies for the necrobump, but I am trying to do something very similar. I am not finding a way to access _LightTexture0 to do a texture lookup (and more importantly, I also need the light space uv coordinates). Any advice?