Reset UV back to 0..1 space

I'm trying to make a custom shader for UI sprites, which can mask every sprite with a single mask texture.

texcoord0 in the shader is used by the atlas and the output coordinates are for the sprites.
So I need texcoord1 to let the mask texture to be mapped with different coordinate, which is back to 0..1 uv space.

Any advice on how to calculate the texcoord1 for the mask texture?

Code (CSharp):

1. Shader "ShaderResetUV"
2. {
3. Properties
4. {
5.     _MainTex ("_MainTex RGBA", 2D) = "white" {}
6.     _MaskTex ("_MaskTex RGBA", 2D) = "white" {}
7. }
8.  
9. Category
10. {
11.     Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
12.     Blend SrcAlpha OneMinusSrcAlpha
13.     Cull Off Lighting Off ZWrite Off
14.     Lighting Off
15.    
16.     SubShader
17.     {
18.         Pass
19.         {
20.             CGPROGRAM
21.             #pragma vertex vert
22.             #pragma fragment frag
23.  
24.             #include "UnityCG.cginc"
25.  
26.             sampler2D _MainTex;
27.             fixed4 _MainTex_ST;
28.             sampler2D _MaskTex;
29.             fixed4 _MaskTex_ST;
30.  
31.             struct appdata_t
32.             {
33.                 fixed4 vertex : POSITION;
34.                 fixed2 texcoord : TEXCOORD0;
35.                 fixed4 color : COLOR;
36.             };
37.  
38.             struct v2f
39.             {
40.                 fixed4 vertex : SV_POSITION;
41.                 fixed2 texcoord : TEXCOORD0;
42.                 fixed2 texcoord1 : TEXCOORD1;
43.                 fixed4 color : COLOR;
44.             };
45.  
46.             v2f vert (appdata_t v)
47.             {
48.                 v2f o;
49.                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
50.                 o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
51.  
52.                 //Reset UV
53.                 o.texcoord1 = o.texcoord; // WHAT TO DO WITH THIS..
54.                 //
55.  
56.                 o.color = v.color;
57.                 return o;
58.             }
59.            
60.             fixed4 frag (v2f i) : SV_Target
61.             {
62.                 fixed4 c = tex2D(_MainTex,i.texcoord);
63.                 fixed mask = tex2D(_MaskTex,i.texcoord1).a;
64.  
65.                 c.rgb = c.rgb*i.color.rgb;
66.                 c.a = c.a*mask*i.color.a;
67.  
68.                 return c;
69.             }
70.             ENDCG
71.         }
72.     }  
73. }
74. }
75.  

 

Have you tried using TEXCOORD1 from the appdata instead of TEXCOORD0? I have no idea if it'll be any different, but worth a try.

 

Yes, I tried. the input texcoord1 value is just the same as texcoord0....

 

I think this is great idea! Could you get succeed?

 

So... there is a PositionAsUV1 Component in Unity. It will give you a BUNCH OF LIES, but might work if you have the right combo of Image mode, and anchor settings...

If it doesn't you'll have to write your own Component to set the UV's on the verts of your UI renderer. This is non-trivial, as you'll have to account for the Image mode and anchoring stuff returning you wacky data, but it can be done.