Passthrough with Shadow

Try this tutorial

Unity AR Foundation - How To Apply Shadows To Transparent AR Planes For More Realistic AR? - YouTube 

So, I updated to URP.  My custom shader no longer works, so I used the UDP/Lit shader.  However, using this shader I can't seem to get a solid shadow on a completely transparent object, so I used the shader from the YouTube video.  That seems to work fine, but again, as soon as I run it in Oculus it just loses that shadow even though it works in the play window.

I think this may be all about which material Oculus are using to render the passthrough.  To get it to work using a UI image as the background, I had to set the material to use Render Queue 'Geometry' (3000) instead of the default (From Shader, 2000).  There seems to be no Render Queue option for Passthrough though.

Double check that your Android quality settings have cast shadows enabled. 

Has anyone successfully got shadow working using OVR Passthrough Layer?

Yes, I've got it to work with URP.

What I think was happening in our case is that the Passthrough Layer was rendered afterwards, and used the alpha value in the framebuffer for blending. So if your shadows are rendering and not setting the alpha to >0, they will be completely overwritten by the passthrough image.

So a good thing to try would be to modify whichever shader renders your shadows to output an alpha value (say 1.0 or 255 to start with).

I finally got it to work.  I had to change the Blend mode and the color output from frag() to get it to work.  The original shader I pinched was...

Shader "URP AR Shadow Receiver"
{
    Properties
    {
        _ShadowColor ("Shadow Color", Color) = (0.35,0.4,0.45,1.0)
    }
 
    SubShader
    {
        Tags
        {
            "RenderPipeline"="UniversalPipeline"
            "RenderType"="Transparent"
            "Queue"="Transparent-1"
        }
 
        Pass
        {
            Name "ForwardLit"
            Tags { "LightMode" = "UniversalForward" }
 
            Blend DstColor Zero, Zero One
            Cull Back
            ZTest LEqual
            ZWrite Off
   
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
 
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            #pragma target 2.0
 
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS_CASCADE
            #pragma multi_compile _ _SHADOWS_SOFT
            #pragma multi_compile_fog
 
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
 
            CBUFFER_START(UnityPerMaterial)
            float4 _ShadowColor;
            CBUFFER_END
 
            struct Attributes
            {
                float4 positionOS : POSITION;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };
 
            struct Varyings
            {
                float4 positionCS               : SV_POSITION;
                float3 positionWS               : TEXCOORD0;
                float fogCoord                  : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };
 
            Varyings vert (Attributes input)
            {
                Varyings output = (Varyings)0;
 
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);
 
                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.positionCS = vertexInput.positionCS;
                output.positionWS = vertexInput.positionWS;
                output.fogCoord = ComputeFogFactor(vertexInput.positionCS.z);
 
                return output;
            }
 
            half4 frag (Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
 
                half4 color = half4(1,1,1,1);
 
            #ifdef _MAIN_LIGHT_SHADOWS
                VertexPositionInputs vertexInput = (VertexPositionInputs)0;
                vertexInput.positionWS = input.positionWS;
 
                float4 shadowCoord = GetShadowCoord(vertexInput);
                half shadowAttenutation = MainLightRealtimeShadow(shadowCoord);
                color = lerp(half4(1,1,1,1), _ShadowColor, (1.0 - shadowAttenutation) * _ShadowColor.a);
                color.rgb = MixFogColor(color.rgb, half3(1,1,1), input.fogCoord);
            #endif
                return color;
            }
 
            ENDHLSL
        }
    }
}

After modification it's now...

Shader "My Shadow Shader"
{
    Properties
    {
        _ShadowColor ("Shadow Color", Color) = (0.35,0.4,0.45,1.0)
    }
 
    SubShader
    {
        Tags
        {
            "RenderPipeline"="UniversalPipeline"
            "RenderType"="Transparent"
            "Queue"="Transparent-1"
        }
 
        Pass
        {
            Name "ForwardLit"
            Tags { "LightMode" = "UniversalForward" }

	Blend SrcAlpha OneMinusSrcAlpha 
            Cull Back
            ZTest LEqual
            ZWrite Off
   
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
 
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            #pragma target 2.0
 
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS_CASCADE
            #pragma multi_compile _ _SHADOWS_SOFT
            #pragma multi_compile_fog
 
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
 
            CBUFFER_START(UnityPerMaterial)
            float4 _ShadowColor;
            CBUFFER_END
 
            struct Attributes
            {
                float4 positionOS : POSITION;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };
 
            struct Varyings
            {
                float4 positionCS               : SV_POSITION;
                float3 positionWS               : TEXCOORD0;
                float fogCoord                  : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };
 
            Varyings vert (Attributes input)
            {
                Varyings output = (Varyings)0;
 
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);
 
                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.positionCS = vertexInput.positionCS;
                output.positionWS = vertexInput.positionWS;
                output.fogCoord = ComputeFogFactor(vertexInput.positionCS.z);
 
                return output;
            }
 
            half4 frag (Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
 
                half4 color = half4(1,1,1,1);
 
            #ifdef _MAIN_LIGHT_SHADOWS
                VertexPositionInputs vertexInput = (VertexPositionInputs)0;
                vertexInput.positionWS = input.positionWS;
 
                float4 shadowCoord = GetShadowCoord(vertexInput);
                half shadowAttenutation = MainLightRealtimeShadow(shadowCoord);
                 color = lerp(half4(0,0,0,0), _ShadowColor, (1.0 - shadowAttenutation));
           #endif
                return color;
            }
 
            ENDHLSL
        }
    }
}

I'm sure due to my lack of experience this is a bit off, but it seems to produce the desired effect.  Next, I will try and project it onto the defined room geometry (walls, floor, desk etc.) that I can hopefully pick up from the SDK.  Really appreciated your pointers here, thank you.

I got this working and I keep replying with my shader code, but my reply keeps getting wiped out.  I don't know why. Anyway, thank you for the pointers, it helped a lot.  I had to modify the 'Blend' to get it to work.

Hi Raeldor,

thanks for your shader! I have the same problem but I cannot make it work! I checked everything pipeline related and any other settings. I used your shader and it shows shadows in the editor but not in the build on my quest 2. Did you also changed settings at the SelectivePassthrough-Material like ZTest or blend alpha?

Thanks for help, Can