Transparent Surface Shader Invisible In front Of UI

I wan't to produce a semi transparent overlay over my UI for which I'm using this simple variant of the standard surface shader in with added transparency:

Code (CSharp):

1. Shader "Custom/FakeUIMaskShader"
2. {
3.     Properties
4.     {
5.         _Color ("Color", Color) = (1,1,1,1)
6.         _MainTex ("Albedo (RGB)", 2D) = "white" {}
7.         _Glossiness ("Smoothness", Range(0,1)) = 0.5
8.         _Metallic ("Metallic", Range(0,1)) = 0.0
9.     }
10.     SubShader
11.     {
12.         Tags { "Queue" = "Overlay+1" "IgnoreProjector" = "True" "RenderType" = "Transparent" }
13.         LOD 100
14.  
15.         Stencil {
16.             Ref 2
17.             Comp Equal
18.         }
19.  
20.         CGPROGRAM
21.         // Physically based Standard lighting model, and enable shadows on all light types
22.         #pragma surface surf Standard fullforwardshadows alpha
23.  
24.         // Use shader model 3.0 target, to get nicer looking lighting
25.         #pragma target 3.0
26.  
27.         sampler2D _MainTex;
28.  
29.         struct Input
30.         {
31.             float2 uv_MainTex;
32.         };
33.  
34.         half _Glossiness;
35.         half _Metallic;
36.         fixed4 _Color;
37.  
38.         // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
39.         // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
40.         // #pragma instancing_options assumeuniformscaling
41.         UNITY_INSTANCING_BUFFER_START(Props)
42.             // put more per-instance properties here
43.         UNITY_INSTANCING_BUFFER_END(Props)
44.  
45.         void surf (Input IN, inout SurfaceOutputStandard o)
46.         {
47.             // Albedo comes from a texture tinted by color
48.             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
49.             o.Albedo = c.rgb;
50.             // Metallic and smoothness come from slider variables
51.             o.Metallic = _Metallic;
52.             o.Smoothness = _Glossiness;
53.             o.Alpha = c.a;
54.         }
55.         ENDCG
56.     }
57.     FallBack "Diffuse"
58. }
59.  

This works fine as long as the object is't in front of my Screen Space Camera UI (UI elements all are using the default unity UI shader). If the object is in front of the UI the UI get's rendered over the object like this:

See the red part is hidden behind the UI inspite of the object (selected) is in front of the UI.

If I remove the alpha pragma, everything works fine (except the transparency missing of course):


The fact that this uses a stencil should be irrelevant, as this also happens when removing the stencil part.

Is there anything I'm missing? Thanks in advance!

 

Hi,
I just ran into a similar problem and solved with adding the two line in Pass function

Code (CSharp):

1.   SubShader {
2.     Pass {
3.       ZWrite On
4.       ColorMask 0
5.     }
6.   }