How to enable Fog in vertex bending shader?

Questions & Answers
1

I recently found a Unity shader that bends the vertex to create a “Subway Surfers” game like effect. This is working beautifully, but it doesn’t seem to support Fog.

Shader "Custom/Curved" {
	Properties {
		_MainTex ("Base (RGB)", 2D) = "white" {}
		_QOffset ("Offset", Vector) = (0,0,0,0)
		_Dist ("Distance", Float) = 100.0
	}
	SubShader {
		Tags { "RenderType"="Opaque" }
		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"

                        sampler2D _MainTex;
			float4 _QOffset;
			float _Dist;
			
			struct v2f {
			    float4 pos : SV_POSITION;
			    float4 uv : TEXCOORD0;
			};

			v2f vert (appdata_base v)
			{
			    v2f o;
			    float4 vPos = mul (UNITY_MATRIX_MV, v.vertex);
			    float zOff = vPos.z/_Dist;
			    vPos += _QOffset*zOff*zOff;
			    o.pos = mul (UNITY_MATRIX_P, vPos);
			    o.uv = v.texcoord;
			    return o;
			}

			half4 frag (v2f i) : COLOR
			{
			    half4 col = tex2D(_MainTex, i.uv.xy);
			    return col;
			}
			ENDCG
		}
	}
	FallBack "Diffuse"
}

I tried altering the “SubShader” section as shown below, but it has created a flickering Fog with no Alpha.

Tags { "RenderType"="transparent" }
		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
            #pragma multi_compile_fog
            
			#include "UnityCG.cginc"

            sampler2D _MainTex;
			float4 _QOffset;
			float _Dist;
			
			struct v2f {
			    float4 pos : SV_POSITION;
			    float4 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
			};

			v2f vert (appdata_base v)
			{
			    v2f o;
			    float4 vPos = mul (UNITY_MATRIX_MV, v.vertex);
			    float zOff = vPos.z/_Dist;
			    vPos += _QOffset*zOff*zOff;
			    o.pos = mul (UNITY_MATRIX_P, vPos);
			    o.uv = v.texcoord;
			    UNITY_TRANSFER_FOG(o,v.vertex);
			    return o;
			}

			half4 frag (v2f i) : COLOR
			{
			    half4 col = tex2D(_MainTex, i.uv.xy);
                
                UNITY_APPLY_FOG(i.fogCoord, col);
                UNITY_OPAQUE_ALPHA(col.a);
                
			    return col;
			}
			ENDCG
		}

Can anyone tell me exactly what I’m doing wrong.

2

UNITY_TRANSFER_FOG(o,v.vertex); is wrong, it should be UNITY_TRANSFER_FOG(o,o.pos);

As for the alpha problem, I don’t know. I would guess it has something to do with UNITY_OPAQUE_ALPHA(col.a); It wasn’t in the original shader that you posted and it’s not needed for fog, so it’s probably not needed.

3

Thanks @Jessespike. I tried those earlier, but they were giving some compilation errors. I merged some code from another shader, and it now supports fog (and hopefully lightmapping as well). Since I’m not a shader programmer, I’m not sure if this is the most optimised way to do it, but at least it’s in a working state right now. I’d again like to thank you for taking out the time to help me.

Shader "Custom/Curved With Fog" {
	Properties {
		_MainTex ("Base (RGB)", 2D) = "white" {}
		_QOffset ("Offset", Vector) = (0,0,0,0)
		_Dist ("Distance", Float) = 100.0
	}
	SubShader {
		Tags { "RenderType"="transparent" "IgnoreProjector"="True" }
		Pass
		{
			CGPROGRAM
			#include "UnityCG.cginc"
			#pragma vertex vert addshadow
			#pragma fragment frag
			#pragma multi_compile_fog
			#pragma multi_compile LIGHTMAP_ON LIGHTMAP_OFF

            sampler2D _MainTex;
			float4 _MainTex_ST;
			float4 _QOffset;
			float _Dist;

			struct appdata_t {
				float4 vertex : POSITION;
				float2 texcoord : TEXCOORD0;
				float2 texcoord1 : TEXCOORD1;
			};

			struct v2f {
			    float4 vertex : SV_POSITION;
			    float2 uv : TEXCOORD0;
				half2 uv2 : TEXCOORD1;
                UNITY_FOG_COORDS(2)
			};

			v2f vert (appdata_t v)
			{
			    v2f o;
			    float4 vPos = mul (UNITY_MATRIX_MV, v.vertex);
			    float zOff = vPos.z/_Dist;
			    vPos += _QOffset*zOff*zOff;

			    o.vertex = mul (UNITY_MATRIX_P, vPos);
				o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
			    o.uv2 = v.texcoord;

			    #ifdef LIGHTMAP_ON
		    	  o.uv2  = v.texcoord1.xy * unity_LightmapST.xy + unity_LightmapST.zw;
			 	#endif
			    UNITY_TRANSFER_FOG(o,o.vertex);

			    return o;
			}

			half4 frag (v2f i) : COLOR
			{
			    half4 col = tex2D(_MainTex, i.uv.xy);
                #ifdef LIGHTMAP_ON
				 half4 lm    = UNITY_SAMPLE_TEX2D(unity_Lightmap, i.uv2 );
				 col.rgb     = col.rgb * DecodeLightmap(lm);
           		 col *= UNITY_LIGHTMODEL_AMBIENT * 10;
           		#endif
            
                UNITY_APPLY_FOG(i.fogCoord, col);
                UNITY_OPAQUE_ALPHA(col.a);
                
			    return col;
			}
			ENDCG
		}
	}
	FallBack "Diffuse"
}