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I have multiple UI Sprites that have their alpha set so you can see what's behind them. I would like to make these UI Sprites ignore other UI Sprites.

So take this first picture. There are 4 UI Sprites that overlay over a part of each other.

Note: These sprites can appear in a random location and the number is unknown, so I thought a Shader would make sense for this.

enter image description here

I would like to still adjust their alpha, but I would like them to ignore each other so that they appear to be 1 image like below.

enter image description here

I tried modifying a Shader, but I couldn't work it out.

// Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt) Shader "UI/Default" { Properties { [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {} _Color ("Tint", Color) = (1,1,1,1) _StencilComp ("Stencil Comparison", Float) = 8 _Stencil ("Stencil ID", Float) = 0 _StencilOp ("Stencil Operation", Float) = 0 _StencilWriteMask ("Stencil Write Mask", Float) = 255 _StencilReadMask ("Stencil Read Mask", Float) = 255 _ColorMask ("Color Mask", Float) = 15 [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0 } SubShader { Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" "PreviewType"="Plane" "CanUseSpriteAtlas"="True" } Stencil { Ref [_Stencil] Comp [_StencilComp] Pass [_StencilOp] ReadMask [_StencilReadMask] WriteMask [_StencilWriteMask] } Cull Off Lighting Off ZWrite Off ZTest [unity_GUIZTestMode] Blend SrcAlpha OneMinusSrcAlpha ColorMask [_ColorMask] Pass { Name "Default" CGPROGRAM #pragma vertex vert #pragma fragment frag #pragma target 2.0 #include "UnityCG.cginc" #include "UnityUI.cginc" #pragma multi_compile __ UNITY_UI_CLIP_RECT #pragma multi_compile __ UNITY_UI_ALPHACLIP struct appdata_t { float4 vertex : POSITION; float4 color : COLOR; float2 texcoord : TEXCOORD0; UNITY_VERTEX_INPUT_INSTANCE_ID }; struct v2f { float4 vertex : SV_POSITION; fixed4 color : COLOR; float2 texcoord : TEXCOORD0; float4 worldPosition : TEXCOORD1; UNITY_VERTEX_OUTPUT_STEREO }; fixed4 _Color; fixed4 _TextureSampleAdd; float4 _ClipRect; v2f vert(appdata_t v) { v2f OUT; UNITY_SETUP_INSTANCE_ID(v); UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT); OUT.worldPosition = v.vertex; OUT.vertex = UnityObjectToClipPos(OUT.worldPosition); OUT.texcoord = v.texcoord; OUT.color = v.color * _Color; return OUT; } sampler2D _MainTex; fixed4 frag(v2f IN) : SV_Target { half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color; #ifdef UNITY_UI_CLIP_RECT color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect); #endif #ifdef UNITY_UI_ALPHACLIP clip (color.a - 0.001); #endif return color; } ENDCG } } }
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    \$\begingroup\$ I answered the same question here \$\endgroup\$ Commented May 2, 2018 at 13:18
  • \$\begingroup\$ @SeyedMortezaKamali Thanks. I did look for a few days to a solution, but I guess my search terms were incorrect. \$\endgroup\$ Commented May 2, 2018 at 14:39

1 Answer 1

Reset to default
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Just change your Stencil like below Image:

Image

Stencil Op/Comparison Values

Comparison Functions

0 - Always 1 - Never 2 - Less 3 - Equal 4 - LEqual 5 - Greater 6 - NotEqual 7 - GEqual 8 - Always // (This is the default for the UI shaders so I suspect this one is technically the 'correct' Always, but any value beyond it will also count as Always)

Stencil Operations

0 - Keep 1 - Zero 2 - Replace 3 - IncrSat 4 - DecrSat 5 - Invert 6 - IncrWrap 7 - DecrWrap

References: unity forum & khronos

Adding Enum to Inspector

It's hard to remember above stencil number so you can use enum

Image

change your properties like this:

[Enum(UnityEngine.Rendering.CompareFunction)] _StencilComp ("Stencil Comparison", Int) = 3 [Enum(UnityEngine.Rendering.StencilOp)] _StencilOp ("Stencil Operation", Int) = 3

useful link : configurableStencil shader

Final Result

Final Result

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  • \$\begingroup\$ Oh wow. Didn't think it was that easy. Been working on a solution for a few days, didn't know a few inspector changes would do that. Thanks for links, will definitely read up on those, and thanks for a simple solution. \$\endgroup\$ Commented May 2, 2018 at 14:40
  • \$\begingroup\$ @SeyedMortezaKamali I've tried your answer provided both in this post and here. It works like a charm... however at the same time it breaks Unity built-in masking (SpriteMask and rect-based Mask). I've created a post on Unity forums about that here My project uses the Universal Render Pipeline and Unity 2019.3. Any advice on how to handle this? \$\endgroup\$ Commented May 2, 2020 at 10:58
  • \$\begingroup\$ @JanMysior: it looks to me like this would be a new question worth its own Question post. Click the "Ask Question" button in the top right to get started. \$\endgroup\$ Commented May 2, 2020 at 12:22

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