Trying to sample the GBuffer.

[winged thorn]

Title, basically. Writing a HLSL shader (despise shader graph in it's entirety) and I can't seem to sample the GBuffer from a shader. I can see that my objects are rendering to _GBuffer0 according to the frame debugger, but when I try to sample _GBuffer0, it just returns a grey color.

I define the GBuffer like so:

TEXTURE2D(_GBuffer0);
SAMPLER(sampler_GBuffer0);

and sample it like so:

float3 n = SAMPLE_TEXTURE2D(_GBuffer0, sampler_GBuffer0, IN.screenPosition/IN.screenPosition.w);

Screen position is calculated in the vertex shader like so:

//Irrelevant parts omitted
VertexPositionInputs positionInputs = GetVertexPositionInputs(IN.positionOS.xyz);
VertexNormalInputs normalInputs = GetVertexNormalInputs(IN.normalOS);
OUT.screenPosition = positionInputs.positionNDC;

It's worth noting I'm not trying to sample this from a fullscreen quad, but specific objects in the scene (the usecase being to sample the GBuffer for drawing edge highlights on objects)

I'm using Unity 6000.3.6f1 and URP version 17.3.0.

This is the entire UniversalGBuffer pass I use to render to the GBuffer.

{
    Name "UniversalGBuffer"
    Tags { "LightMode" ="UniversalGBuffer" }
    HLSLPROGRAM
    #pragma vertex LitGBufferPassVertex
    #pragma fragment LitGBufferPassFragment
    struct Attributes
    {
        float4 positionOS   : POSITION;
        float3 normalOS     : NORMAL;
        float4 tangentOS    : TANGENT;
        float2 texcoord     : TEXCOORD0;
        float2 staticLightmapUV   : TEXCOORD1;
        float2 dynamicLightmapUV  : TEXCOORD2;
    };

    struct Varyings
    {
        float2 uv                       : TEXCOORD0;
        half3 normalWS                  : TEXCOORD2;
        float4 positionCS               : SV_POSITION;
    };


    //Vertex shader
    Varyings LitGBufferPassVertex(Attributes IN)
    {
         Varyings OUT;
        
        VertexPositionInputs positionInputs = GetVertexPositionInputs(IN.positionOS.xyz);
        VertexNormalInputs normalInputs = GetVertexNormalInputs(IN.normalOS);



        OUT.positionCS = positionInputs.positionCS;
        OUT.uv = IN.texcoord;
        OUT.normalWS = normalInputs.normalWS;

        return OUT;
    }

    float4 LitGBufferPassFragment(Varyings IN) : SV_Target {
        float3 normal = normalize(IN.normalWS);

        normal = normal * 0.5 + 0.5;
        
        return float4(normal,1);
    }
    
    ENDHLSL
}

[fierce sequoia]

If you just need normal data I'd try the built-in _CameraNormalsTexture first (see DeclareNormalsTexture.hlsl include file under the URP ShaderLibrary)

Otherwise you may be able to use a renderer feature to expose the gbuffers as global textures. e.g. https://github.com/Unity-Technologies/Graphics/blob/master/Packages/com.unity.render-pipelines.universal/Samples~/URPRenderGraphSamples/GlobalGbuffers/GlobalGbuffersRendererFeature.cs

[winged thorn]

tried both of those, couldn't get anything to work.

[winged thorn]

I've also tried sampling all the other _GBufferX textures (i.e. _GBuffer1, _GBuffer2, etc). Can only get grey.

https://discussions.unity.com/t/trying-to-use-gbuffer-rt0-and-only-get-a-grey-screen/180573 I found this, but it's for BIRP and the solution they found (not using deferred on camera) doesn't work for me as I've checked and made sure I'm using Deferred (and also tried Deferred+)

also triple checked that I'm using the correct pipeline asset, which I am.

It's maybe worth noting I can sample depth fine as long as the shader is using the transparent queue. It otherwise uses the standard geometry queue

[tired pasture]

This may be because these textures are still writable pre this stage or a copy is made only post opaque

[winged thorn]

I've got them to be green.

float3 normals = SampleSceneNormals(IN.screenPosition.xy/IN.screenPosition.w);
return float4(normals.xyz,1);