RGB alpha mask shader with 3 uv-sets?

Is it possible to change this shader so that it uses 3 uv-sets? So basically we have a mesh with 3 different materials and we need it to just have one material and guessing that will be possible if the mesh has 3 uv-sets instead?


// Unlit alpha-blended shader.
// - no lighting
// - no lightmap support
// - no per-material color

Shader "Unlit/AlphaMask" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_AlphaTex ("Alpha mask (R)", 2D) = "white" {}
}

SubShader {
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
LOD 100

ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha

Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"

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

struct v2f {
float4 vertex : SV_POSITION;
half2 texcoord : TEXCOORD0;
};

sampler2D _MainTex;
sampler2D _AlphaTex;

float4 _MainTex_ST;

v2f vert (appdata_t v)
{
v2f o;
o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
return o;
}

fixed4 frag (v2f i) : SV_Target
{
fixed4 col = tex2D(_MainTex, i.texcoord);
fixed4 col2 = tex2D(_AlphaTex, i.texcoord);

return fixed4(col.r, col.g, col.b, col2.r);
}
ENDCG
}
}

}

 

I don't really know much about writing shaders, but i have been able to get pretty close to where i want to be. The problem now seems to be that col1, col2 and col3 takes a color value from all the textures, no matter if the fbx has any uv assigned to some area for a specific uv-channel. I would want col2 for example be 0 if there is no uv for it. Is that doable? Here is the shader so far.

Shader "Unlit/AlphaMask_CombinedMesh" {
Properties {
_MainTex1 ("Uv1 (RGB)", 2D) = "" {}
_AlphaTex1 ("Uv1 Alpha mask (R)", 2D) = "" {}
_MainTex2 ("Uv2 (RGB)", 2D) = "" {}
_AlphaTex2 ("Uv2 Alpha mask (R)", 2D) = "" {}
_MainTex3 ("Uv3 (RGB)", 2D) = "" {}
_AlphaTex3 ("Uv3 Alpha mask (R)", 2D) = "" {}
}

SubShader {
Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
LOD 100

ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha

Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag

#include "UnityCG.cginc"

struct appdata_t {
float4 vertex : POSITION;
float2 texcoord1 : TEXCOORD0;
float2 texcoord2 : TEXCOORD1;
float2 texcoord3 : TEXCOORD2;
};

struct v2f {
float4 pos : SV_POSITION;
half2 uv1 : TEXCOORD0;
half2 uv2 : TEXCOORD1;
half2 uv3 : TEXCOORD2;
};

sampler2D _MainTex1;
sampler2D _AlphaTex1;
sampler2D _MainTex2;
sampler2D _AlphaTex2;
sampler2D _MainTex3;
sampler2D _AlphaTex3;

float4 _MainTex1_ST;
float4 _MainTex2_ST;
float4 _MainTex3_ST;

v2f vert (appdata_t v)
{
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
o.uv1 = TRANSFORM_TEX(v.texcoord1, _MainTex1);
o.uv2 = TRANSFORM_TEX(v.texcoord2, _MainTex2);
o.uv3 = TRANSFORM_TEX(v.texcoord3, _MainTex3);
return o;
}

fixed4 frag (v2f i) : SV_Target
{
fixed4 col1 = tex2D(_MainTex1, i.uv1);
fixed4 colalpha1 = tex2D(_AlphaTex1, i.uv1);

fixed4 col2 = tex2D(_MainTex2, i.uv2);
fixed4 colalpha2 = tex2D(_AlphaTex2, i.uv2);

fixed4 col3 = tex2D(_MainTex3, i.uv3);
fixed4 colalpha3 = tex2D(_AlphaTex3, i.uv3);

return fixed4(col1.r + col2.r + col3.r, col1.g + col2.g + col3.g, col1.b + col2.b + col3.b, colalpha1.r + colalpha2.r + colalpha3.r);
}
ENDCG
}
}

}