Question by ecorreafechner · Nov 09, 2019 at 07:02 PM · c#post processing post-process-effect visual-effects post-processing

How to use Post Processing Stack with stencil masking shaders

Hi, So I want to create a post processing effect that affects only an area of the screen in one way and have the rest be affected differently. For example have a sphere around the player position render normally and the rest render in black and white. For this I created a shader that writes to the stencil, not really rendering anything, and put the material to a sphere. Properties { [PerRendererData]_MainTex ("Texture", 2D) = "white" {} } SubShader{ Tags{ "RenderType" = "Opaque" "Queue" = "Geometry" } ColorMask 0 ZWrite off Stencil { Ref 120 Comp always Pass replace } Pass { CGPROGRAM #pragma vertex vert #pragma fragment frag

             #include "UnityCG.cginc"
 
             struct appdata
             {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
             };
 
             struct v2f
             {
                 float2 uv : TEXCOORD0;
                 float4 vertex : SV_POSITION;
             };
 
             v2f vert (appdata v)
             {
                 v2f o;
                 o.vertex = UnityObjectToClipPos(v.vertex);
                 o.uv = v.uv;
                 return o;
             }
 
             sampler2D _MainTex;
 
             fixed4 frag (v2f i) : SV_Target
             {
                 return (0,0,0,0);
             }
             ENDCG
         }
     }

Then I created a shader that renders normally if the stencil is the same and black and white if it's different. HLSLINCLUDE

         #include "Assets/PostProcessing-2/PostProcessing-2/PostProcessing/Shaders/StdLib.hlsl"
 
         TEXTURE2D_SAMPLER2D(_MainTex, sampler_MainTex);
 
         float4 FragGrayscale(VaryingsDefault i) : SV_Target
         {
             float4 color = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoord);
             float luminance = dot(color.rgb, float3(0.2126729, 0.7151522, 0.0721750));
             color.rgb = luminance.xxx;
             return color;
         }
         float4 Frag(VaryingsDefault i) : SV_Target
         {
             float4 color = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.texcoord);
             return color;
         }
 
     ENDHLSL
 
     SubShader
     {
         Cull Off ZWrite Off ZTest Always
 
         Pass
         {
             Stencil
             {
                 Ref 120
                 Comp equal
                 Pass keep
             }
             HLSLPROGRAM
 
                 #pragma vertex VertDefault
                 #pragma fragment FragGrayscale
 
             ENDHLSL
         }
         Pass
         {
             Stencil
             {
                 Ref 120
                 Comp equal
                 Pass keep
             }
             HLSLPROGRAM
 
                 #pragma vertex VertDefault
                 #pragma fragment Frag
 
             ENDHLSL
         }
     }

However the post processing stack seems to simply ignore the stencil part of the pass, I assume because no 'depth' or 'stencil' info is being sent with the source texture, but I don't know how exactly I can access this information. Also the post processing stack only uses one of the shader pass, which I don't know how to change but could call BlitFullscreenTriangle twice, once for each pass if needded. This is the code for the custom effect I have:

 public sealed class PossessionAreaFXRenderer : PostProcessEffectRenderer<PossessionAreaFX>
 {
     public override void Render(PostProcessRenderContext context)
     {
         var sheet = context.propertySheets.Get(Shader.Find("Hidden/PossessionEffect"));
         context.sourceFormat = RenderTextureFormat.Depth;
         context.command.BlitFullscreenTriangle(context.source, context.destination, sheet, 0);
     }
 }

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