Duplicated system values in unlit shader (Unity) - unity3d

Question

Im pretty new to scripting shaders and i was trying to make a unlit shader work so it generates an outline around the object and lets me interpolate between 2 diferent textures, but I get 3 errors:
·Shader error in 'Unlit/Both': Duplicate system value semantic definition: output semantic 'POSITION' and output semantic 'SV_POSITION' at line 38
·Shader error in 'Unlit/Both': Duplicate system value semantic definition: input semantic 'SV_POSITION' and input semantic 'POSITION' at line 39
·Shader error in 'Unlit/Both': Duplicate system value semantic definition: output semantic 'SV_POSITION' and output semantic 'POSITION' at line 39
I guess there is something wrong with the position values but i have no idea about what to do so if anyone knows how to fix it i would be so thankful
{
Properties
{
_Color("Main Color", Color) = (0.5,0.5,0.5,1)
_MainTex ("Texture", 2D) = "white" {}
_SecondaryTex ("2nd Texture", 2D) = "white" {}
_LerpValue("Transition float", Range(0,1))= 0.5
_OutlineColor("Outline color", color) = (0,0,0,1)
_OutlineWidth("Outline width", Range(1.0,5.0)) = 1.01
}
SubShader
{
Tags { "RenderType"="Opaque" }
LOD 100
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
float3 normal : NORMAL;
};
struct v2f
{
float2 uv : TEXCOORD0;
UNITY_FOG_COORDS(1)
float4 vertex : SV_POSITION;
float4 pos : POSITION;
float3 normal : NORMAL;
};
sampler2D _MainTex;
float4 _MainTex_ST;
sampler2D _SecondaryTex;
float4 _SecondaryTex_ST;
float4 _LerpValue;
float _OutlineWidth;
float4 _OutlineColor;
v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
UNITY_TRANSFER_FOG(o,o.vertex);
v.vertex.xyz *= _OutlineWidth;
o.pos = UnityObjectToClipPos(v.vertex);
return o;
}
fixed4 frag(v2f i) : SV_Target
{
fixed4 col = lerp(tex2D(_MainTex, i.uv), tex2D(_SecondaryTex, i.uv),_LerpValue);
return col;
}
ENDCG
}
}
SubShader
{
Tags{"Queue" = "Transparent"}
Pass//Render the Outline
{
ZWrite Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
half4 frag(v2f i) : COLOR
{
return _OutlineColor;
}
ENDCG
}
Pass//Normal render
{
ZWrite On
Material
{
Diffuse[_Color]
Ambient[_Color]
}
Lighting On
SetTexture[_MainTex]
{
ConstantColor[_Color]
}
SetTexture[_MainTex]
{
Combine previous * primary DOUBLE
}
}
}
}

Answer 1

When you want to pass data from vertex shader to pixel shader you need to use TEXCOORD as semantic, in this case, you should change the 'POSITION' semantic with 'TEXCOORD2'(in v2f struct).
Semantics will specify what data you are passing(actually how to
interpret data). The first stage in the pipeline is IA(Input
Assembler) when you pass data from IA to vertex shader you use
semantic to know which property you are using, for example, in your 'appdata' struct, vertex is POSITION so when the data(like geometry,3d objects) is passed to the IA stage you need to know which data you are using in the GPU so by using semantic you can easily find the properties of each object(each object must have position and it's better to have normal, tangent, color,....)