Standard Shader - 2 Sided (cull off) - Also, 2 Sided Standard Surface Shader with Fixed Normals

Standard-2Sided-FixNormals.shader

// 2 sided standard surface shader (using 2 passes), with fixed normals for flipped faces

Shader "Custom/TwoSided (FixedNormals)"
{
    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
		Cull Back

		CGPROGRAM
		// Physically based Standard lighting model, and enable shadows on all light types
		#pragma surface surf Standard fullforwardshadows

		// Use shader model 3.0 target, to get nicer looking lighting
		#pragma target 3.0

		sampler2D _MainTex;

		struct Input
		{
			float2 uv_MainTex;
		};

		half _Glossiness;
		half _Metallic;
		fixed4 _Color;

		// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
		// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
		// #pragma instancing_options assumeuniformscaling
		UNITY_INSTANCING_BUFFER_START(Props)
			// put more per-instance properties here
		UNITY_INSTANCING_BUFFER_END(Props)

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

		// 2nd pass to fix flipped normals
		Tags{ "RenderType" = "Opaque" }
		LOD 200
		Cull Front

		CGPROGRAM
		// Physically based Standard lighting model, and enable shadows on all light types
		#pragma surface surf Standard fullforwardshadows
		#pragma vertex vert

		// Use shader model 3.0 target, to get nicer looking lighting
		#pragma target 3.0

		sampler2D _MainTex;

		struct Input
		{
			float2 uv_MainTex;
		};

		half _Glossiness;
		half _Metallic;
		fixed4 _Color;

		// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
		// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
		// #pragma instancing_options assumeuniformscaling
		UNITY_INSTANCING_BUFFER_START(Props)
		// put more per-instance properties here
		UNITY_INSTANCING_BUFFER_END(Props)

		void vert(inout appdata_full v, out Input o) {
			UNITY_INITIALIZE_OUTPUT(Input, o);
			v.normal = -v.normal;
		}

		void surf(Input IN, inout SurfaceOutputStandard o)
		{
			// Albedo comes from a texture tinted by color
			fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * _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"
}

Standard-2Sided.shader

// Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)

Shader "Standard 2-Sided"
{
	Properties
	{
		_Color("Color", Color) = (1,1,1,1)
		_MainTex("Albedo", 2D) = "white" {}
		
		_Cutoff("Alpha Cutoff", Range(0.0, 1.0)) = 0.5

		_Glossiness("Smoothness", Range(0.0, 1.0)) = 0.5
		_GlossMapScale("Smoothness Scale", Range(0.0, 1.0)) = 1.0
		[Enum(Metallic Alpha,0,Albedo Alpha,1)] _SmoothnessTextureChannel ("Smoothness texture channel", Float) = 0

		[Gamma] _Metallic("Metallic", Range(0.0, 1.0)) = 0.0
		_MetallicGlossMap("Metallic", 2D) = "white" {}

		[ToggleOff] _SpecularHighlights("Specular Highlights", Float) = 1.0
		[ToggleOff] _GlossyReflections("Glossy Reflections", Float) = 1.0

		_BumpScale("Scale", Float) = 1.0
		_BumpMap("Normal Map", 2D) = "bump" {}

		_Parallax ("Height Scale", Range (0.005, 0.08)) = 0.02
		_ParallaxMap ("Height Map", 2D) = "black" {}

		_OcclusionStrength("Strength", Range(0.0, 1.0)) = 1.0
		_OcclusionMap("Occlusion", 2D) = "white" {}

		_EmissionColor("Color", Color) = (0,0,0)
		_EmissionMap("Emission", 2D) = "white" {}
		
		_DetailMask("Detail Mask", 2D) = "white" {}

		_DetailAlbedoMap("Detail Albedo x2", 2D) = "grey" {}
		_DetailNormalMapScale("Scale", Float) = 1.0
		_DetailNormalMap("Normal Map", 2D) = "bump" {}

		[Enum(UV0,0,UV1,1)] _UVSec ("UV Set for secondary textures", Float) = 0


		// Blending state
		[HideInInspector] _Mode ("__mode", Float) = 0.0
		[HideInInspector] _SrcBlend ("__src", Float) = 1.0
		[HideInInspector] _DstBlend ("__dst", Float) = 0.0
		[HideInInspector] _ZWrite ("__zw", Float) = 1.0
	}

	CGINCLUDE
		#define UNITY_SETUP_BRDF_INPUT MetallicSetup
	ENDCG

	SubShader
	{
		Tags { "RenderType"="Opaque" "PerformanceChecks"="False" }
		LOD 300
	

		// ------------------------------------------------------------------
		//  Base forward pass (directional light, emission, lightmaps, ...)
		Pass
		{
			Name "FORWARD" 
			Tags { "LightMode" = "ForwardBase" }

			Blend [_SrcBlend] [_DstBlend]
			ZWrite [_ZWrite]
			
			Cull Off

			CGPROGRAM
			#pragma target 3.0

			// -------------------------------------

			#pragma shader_feature _NORMALMAP
			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _EMISSION
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature ___ _DETAIL_MULX2
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature _ _SPECULARHIGHLIGHTS_OFF
			#pragma shader_feature _ _GLOSSYREFLECTIONS_OFF
			#pragma shader_feature _PARALLAXMAP

			#pragma multi_compile_fwdbase
			#pragma multi_compile_fog
			#pragma multi_compile_instancing

			#pragma vertex vertBase
			#pragma fragment fragBase
			#include "UnityStandardCoreForward.cginc"

			ENDCG
		}
		// ------------------------------------------------------------------
		//  Additive forward pass (one light per pass)
		Pass
		{
			Name "FORWARD_DELTA"
			Tags { "LightMode" = "ForwardAdd" }
			Blend [_SrcBlend] One
			Fog { Color (0,0,0,0) } // in additive pass fog should be black
			ZWrite Off
			ZTest LEqual
			Cull Off

			CGPROGRAM
			#pragma target 3.0

			// -------------------------------------


			#pragma shader_feature _NORMALMAP
			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature _ _SPECULARHIGHLIGHTS_OFF
			#pragma shader_feature ___ _DETAIL_MULX2
			#pragma shader_feature _PARALLAXMAP

			#pragma multi_compile_fwdadd_fullshadows
			#pragma multi_compile_fog

			#pragma vertex vertAdd
			#pragma fragment fragAdd
			#include "UnityStandardCoreForward.cginc"

			ENDCG
		}
		// ------------------------------------------------------------------
		//  Shadow rendering pass
		Pass {
			Name "ShadowCaster"
			Tags { "LightMode" = "ShadowCaster" }

			ZWrite On ZTest LEqual

			CGPROGRAM
			#pragma target 3.0

			// -------------------------------------


			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _PARALLAXMAP
			#pragma multi_compile_shadowcaster
			#pragma multi_compile_instancing

			#pragma vertex vertShadowCaster
			#pragma fragment fragShadowCaster

			#include "UnityStandardShadow.cginc"

			ENDCG
		}
		// ------------------------------------------------------------------
		//  Deferred pass
		Pass
		{
			Name "DEFERRED"
			Tags { "LightMode" = "Deferred" }

			CGPROGRAM
			#pragma target 3.0
			#pragma exclude_renderers nomrt


			// -------------------------------------

			#pragma shader_feature _NORMALMAP
			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _EMISSION
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature _ _SPECULARHIGHLIGHTS_OFF
			#pragma shader_feature ___ _DETAIL_MULX2
			#pragma shader_feature _PARALLAXMAP

			#pragma multi_compile_prepassfinal
			#pragma multi_compile_instancing

			#pragma vertex vertDeferred
			#pragma fragment fragDeferred

			#include "UnityStandardCore.cginc"

			ENDCG
		}

		// ------------------------------------------------------------------
		// Extracts information for lightmapping, GI (emission, albedo, ...)
		// This pass it not used during regular rendering.
		Pass
		{
			Name "META" 
			Tags { "LightMode"="Meta" }

			Cull Off

			CGPROGRAM
			#pragma vertex vert_meta
			#pragma fragment frag_meta

			#pragma shader_feature _EMISSION
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature ___ _DETAIL_MULX2
			#pragma shader_feature EDITOR_VISUALIZATION

			#include "UnityStandardMeta.cginc"
			ENDCG
		}
	}

	SubShader
	{
		Tags { "RenderType"="Opaque" "PerformanceChecks"="False" }
		LOD 150

		// ------------------------------------------------------------------
		//  Base forward pass (directional light, emission, lightmaps, ...)
		Pass
		{
			Name "FORWARD" 
			Tags { "LightMode" = "ForwardBase" }

			Blend [_SrcBlend] [_DstBlend]
			ZWrite [_ZWrite]
			Cull Off

			CGPROGRAM
			#pragma target 2.0
			
			#pragma shader_feature _NORMALMAP
			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _EMISSION 
			#pragma shader_feature _METALLICGLOSSMAP 
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature _ _SPECULARHIGHLIGHTS_OFF
			#pragma shader_feature _ _GLOSSYREFLECTIONS_OFF
			// SM2.0: NOT SUPPORTED shader_feature ___ _DETAIL_MULX2
			// SM2.0: NOT SUPPORTED shader_feature _PARALLAXMAP

			#pragma skip_variants SHADOWS_SOFT DIRLIGHTMAP_COMBINED

			#pragma multi_compile_fwdbase
			#pragma multi_compile_fog

			#pragma vertex vertBase
			#pragma fragment fragBase
			#include "UnityStandardCoreForward.cginc"

			ENDCG
		}
		// ------------------------------------------------------------------
		//  Additive forward pass (one light per pass)
		Pass
		{
			Name "FORWARD_DELTA"
			Tags { "LightMode" = "ForwardAdd" }
			Blend [_SrcBlend] One
			Fog { Color (0,0,0,0) } // in additive pass fog should be black
			ZWrite Off
			ZTest LEqual
			Cull Off
			
			CGPROGRAM
			#pragma target 2.0

			#pragma shader_feature _NORMALMAP
			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature _ _SPECULARHIGHLIGHTS_OFF
			#pragma shader_feature ___ _DETAIL_MULX2
			// SM2.0: NOT SUPPORTED shader_feature _PARALLAXMAP
			#pragma skip_variants SHADOWS_SOFT
			
			#pragma multi_compile_fwdadd_fullshadows
			#pragma multi_compile_fog
			
			#pragma vertex vertAdd
			#pragma fragment fragAdd
			#include "UnityStandardCoreForward.cginc"

			ENDCG
		}
		// ------------------------------------------------------------------
		//  Shadow rendering pass
		Pass {
			Name "ShadowCaster"
			Tags { "LightMode" = "ShadowCaster" }
			
			ZWrite On ZTest LEqual

			CGPROGRAM
			#pragma target 2.0

			#pragma shader_feature _ _ALPHATEST_ON _ALPHABLEND_ON _ALPHAPREMULTIPLY_ON
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma skip_variants SHADOWS_SOFT
			#pragma multi_compile_shadowcaster

			#pragma vertex vertShadowCaster
			#pragma fragment fragShadowCaster

			#include "UnityStandardShadow.cginc"

			ENDCG
		}

		// ------------------------------------------------------------------
		// Extracts information for lightmapping, GI (emission, albedo, ...)
		// This pass it not used during regular rendering.
		Pass
		{
			Name "META" 
			Tags { "LightMode"="Meta" }

			Cull Off

			CGPROGRAM
			#pragma vertex vert_meta
			#pragma fragment frag_meta

			#pragma shader_feature _EMISSION
			#pragma shader_feature _METALLICGLOSSMAP
			#pragma shader_feature _ _SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A
			#pragma shader_feature ___ _DETAIL_MULX2
			#pragma shader_feature EDITOR_VISUALIZATION

			#include "UnityStandardMeta.cginc"
			ENDCG
		}
	}


	FallBack "VertexLit"
	CustomEditor "StandardShaderGUI"
}

only if this engine had anything good in it they prefer engine preformance over anything else everything is code engine sucks balls