Question Trying to cut transparency into a semi-transparent surface, but it has to be opaque?

Hey what's up. I 've got an HLSL shader that cuts a circle around a point, by setting the pixel alphas to 0.

I am running into an issue however, where changing the alpha of the surface removes the cutouts. If I lower the alpha to anything but 1, the cutouts disappear, and the surface becomes uniformly transparent. I suspect this has to do with the settings I'm using in my Shader Pass.

Is there a specific configuration in HLSL that allows for affecting the transparency of an already transparent fragment? I've not found a good answer for this online.

 

Maybe the alpha clip value is really high?
Maybe share the shader code

 

Here's the shader code. I'm really roughing it out right now in HLSL, so I am sure there are improvements to be made. I am not familiar with the alpha clipping you mentioned, I likely haven't configured that properly in the shader.

Code (CSharp):

1. Shader "Unlit/UnlitFOW"
2. {
3.     Properties
4.     {
5.         _MainColor ("Color", Color) = (0,0,0,1)
6.         _MainTex ("Texture", 2D) = "white" {}
7.     }
8.     SubShader
9.     {
10.         Tags { "RenderType"="Transparent" "Queue" = "Transparent" }
11.         LOD 100
12.  
13.         Pass
14.         {
15.             Blend SrcAlpha OneMinusSrcAlpha
16.             ZWrite Off
17.  
18.             HLSLPROGRAM
19.             #pragma vertex vert
20.             #pragma fragment frag
21.  
22.             #include "UnityCG.cginc"
23.  
24.             struct appdata
25.             {
26.                 float4 vertex : POSITION;
27.                 float2 uv : TEXCOORD0;
28.             };
29.  
30.             struct v2f
31.             {
32.                 float4 vertex : SV_POSITION;
33.                 float2 uv : TEXCOORD0;              
34.             };
35.  
36.             struct VisionData
37.             {
38.                 float2 uv;
39.                 float radius;
40.             };
41.  
42.             float4 _MainColor;
43.             sampler2D _MainTex;
44.             float4 _MainTex_ST;
45.             uint _VisionCount;
46.  
47.             StructuredBuffer<VisionData> _VisionData;
48.  
49.             v2f vert (appdata v)
50.             {
51.                 v2f o;
52.                 o.vertex = UnityObjectToClipPos(v.vertex);
53.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
54.                 return o;
55.             }
56.  
57.             half4 frag (v2f i) : SV_Target
58.             {
59.                 float dist = 0;
60.                 half4 col = _MainColor;
61.                
62.                 for(int j = 0; j < _VisionCount; j++)
63.                 {
64.                     if(col.w == 1)
65.                     {
66.                         dist = length(i.uv + _VisionData[j].uv) - _VisionData[j].radius;
67.                         col = dist > 0 ? _MainColor : half4(0,0,0,0);
68.                     }
69.                 }
70.                 return col;
71.             }
72.             ENDHLSL
73.         }
74.     }
75. }

 

Code (CSharp):

1. for(int j = 0; j < _VisionCount; j++)
2.                 {
3.                     if(col.w == 1)
4.                     {
5.                         dist = length(i.uv + _VisionData[j].uv) - _VisionData[j].radius;
6.                         col = dist > 0 ? _MainColor : half4(0,0,0,0);
7.                     }
8.                 }
9.                 return col;

Here you check if the alpha is 1, where you do a distance check and return a blank pixel or the main color

 

I see what you mean now... I forgot to variabalize the check for a variable transparency on the main color... That will probably be the culprit. Good catch!

 

In my shader loop, I had:

Code (CSharp):

1. for(int j = 0; j < _VisionCount; j++)
2.                 {
3.                     if(col.w == 1)
4.                     {
5.                         dist = length(i.uv + _VisionData[j].uv) - _VisionData[j].radius;
6.                         col = dist > 0 ? _MainColor : half4(0,0,0,0);
7.                     }
8.                 }

But it actually needed to be:

Code (CSharp):

1. for(int j = 0; j < _VisionCount; j++)
2.                 {
3.                     if(col.w == _MainColor.w)
4.                     {
5.                         dist = length(i.uv + _VisionData[j].uv) - _VisionData[j].radius;
6.                         col = dist > 0 ? _MainColor : half4(0,0,0,0);
7.                     }
8.                 }

Thanks to DevDunk for pointing this out above.