Question Shader for user-facing camera human occlusion

Hi all, I'm tantalizingly close to getting human occlusion working with the user-facing camera, but I've hit a wall with what I suspect is probably a relatively simple shader issue.



Like the author of this excellent thread, I'm blitting the human stencil texture to a material and setting the camera image to a second texture named "_CameraTex" on the same material. The key line in the shader below is line 101 (lightly adapted from ar-foundation-samples HumanStencil.shader). The frag function returns RGB from the camera texture, but returns the stencil's red channel for the alpha channel.

My intuition is that this should return alpha 0 when the human stencil (second image) is black and alpha 1 when it's red. However, I'm getting that third image, which is successfully returning alpha 0 for all black areas on the stencil texture, but seems to be doing that with the darker areas of _CameraTex, too.

If someone could point me in the right direction, I'd be very grateful!

Code (CSharp):

1. Shader "Unlit/HumanStencil"
2. {
3.     Properties
4.     {
5.         _MainTex ("Main Texture", 2D) = "black" {} //human stencil, blitted
6.         _CameraTex ("Camera Texture", 2D) = "black" {}
7.     }
8.     SubShader
9.     {
10.         Tags
11.         {
12.             "Queue" = "Transparent"
13.             "RenderType" = "Transparent"
14.             "ForceNoShadowCasting" = "True"
15.         }
16.  
17.         Pass
18.         {
19.             Blend SrcAlpha OneMinusSrcAlpha
20.             Cull Off
21.             ZTest Always
22.             ZWrite Off
23.             Lighting Off
24.             LOD 100
25.             Tags
26.             {
27.                 "LightMode" = "Always"
28.             }
29.  
30.  
31.             HLSLPROGRAM
32.  
33.             #pragma vertex vert
34.             #pragma fragment frag
35.  
36.             #include "UnityCG.cginc"
37.  
38.             #define real half
39.             #define real3 half3
40.             #define real4 half4
41.             #define TransformObjectToHClip UnityObjectToClipPos
42.  
43.             #define DECLARE_TEXTURE2D_FLOAT(texture) UNITY_DECLARE_TEX2D_FLOAT(texture)
44.             #define DECLARE_SAMPLER_FLOAT(sampler)
45.             #define SAMPLE_TEXTURE2D(texture,sampler,texcoord) UNITY_SAMPLE_TEX2D(texture,texcoord)
46.  
47.  
48.             struct appdata
49.             {
50.                 float3 position : POSITION;
51.                 float2 texcoord : TEXCOORD0;
52.  
53.                 UNITY_VERTEX_INPUT_INSTANCE_ID
54.             };
55.  
56.             struct v2f
57.             {
58.                 float4 position : SV_POSITION;
59.                 float2 texcoord : TEXCOORD0;
60.  
61.                 UNITY_VERTEX_OUTPUT_STEREO
62.             };
63.  
64.             struct fragment_output
65.             {
66.                 real4 color : SV_Target;
67.             };
68.  
69.  
70.             CBUFFER_START(DisplayRotationPerFrame)
71.             float4x4 _DisplayRotationPerFrame;
72.             CBUFFER_END
73.  
74.  
75.             v2f vert (appdata v)
76.             {
77.                 v2f o;
78.  
79.                 UNITY_SETUP_INSTANCE_ID(v);
80.                 UNITY_INITIALIZE_OUTPUT(v2f, o);
81.                 UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
82.  
83.                 o.position = TransformObjectToHClip(v.position);
84.                 o.texcoord = mul(float3(v.texcoord, 1.0f), _DisplayRotationPerFrame).xy;
85.                 return o;
86.             }
87.  
88.  
89.             DECLARE_TEXTURE2D_FLOAT(_MainTex);
90.             DECLARE_SAMPLER_FLOAT(sampler_MainTex);
91.             DECLARE_TEXTURE2D_FLOAT(_CameraTex);
92.  
93.             fragment_output frag (v2f i)
94.             {
95.                 UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);
96.  
97.                 half4 mask = UNITY_SAMPLE_TEX2D(_MainTex, i.texcoord);
98.                 half4 cam = UNITY_SAMPLE_TEX2D(_CameraTex, i.texcoord);
99.  
100.                 fragment_output o;
101.                 o.color = half4(cam.r, cam.g, cam.b, mask.r);
102.  
103.                 return o;
104.             }
105.  
106.             ENDHLSL
107.         }
108.     }
109. }
110.  

 

Did you ever figure out how to do this? I'm trying to do something similar and would love to see the script you. used to blit the human stencil texture