Problems sampling D3D11 depth buffer

Question

I'm getting everything ready in a little DirectX 11.0 project of mine for a deferred rendering pipeline. However, I've been having quite a lot of trouble with sampling the depth buffer from within a pixel shader.

First I define the depth texture and its shader resource view:

    D3D11_TEXTURE2D_DESC depthTexDesc;
    ZeroMemory(&depthTexDesc, sizeof(depthTexDesc));
    depthTexDesc.Width = nWidth;
    depthTexDesc.Height = nHeight;
    depthTexDesc.Format = DXGI_FORMAT_R32_TYPELESS;
    depthTexDesc.Usage = D3D11_USAGE_DEFAULT;
    depthTexDesc.BindFlags = D3D11_BIND_DEPTH_STENCIL | D3D11_BIND_SHADER_RESOURCE;
    depthTexDesc.MipLevels = 1;
    depthTexDesc.ArraySize = 1;
    depthTexDesc.SampleDesc.Count = 1;
    depthTexDesc.SampleDesc.Quality = 0;
    depthTexDesc.CPUAccessFlags = 0;
    depthTexDesc.MiscFlags = 0;

    hresult = d3dDevice_->CreateTexture2D(&depthTexDesc, nullptr, &depthTexture_);

    D3D11_DEPTH_STENCIL_VIEW_DESC DSVDesc;
    ZeroMemory(&DSVDesc, sizeof(DSVDesc));
    DSVDesc.Format = DXGI_FORMAT_D32_FLOAT;
    DSVDesc.ViewDimension = D3D11_DSV_DIMENSION_TEXTURE2D;
    DSVDesc.Texture2D.MipSlice = 0;

    hresult = d3dDevice_->CreateDepthStencilView(depthTexture_, &DSVDesc, &depthView_);

    D3D11_SHADER_RESOURCE_VIEW_DESC gbDepthTexDesc;
    ZeroMemory(&gbDepthTexDesc, sizeof(gbDepthTexDesc));
    gbDepthTexDesc.Format = DXGI_FORMAT_R32_FLOAT;
    gbDepthTexDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
    gbDepthTexDesc.Texture2D.MipLevels = 1;
    gbDepthTexDesc.Texture2D.MostDetailedMip = -1;

    d3dDevice_->CreateShaderResourceView(depthTexture_, &gbDepthTexDesc, &gbDepthView_);

Here's the relevant part of my rendering function:

    float clearColor[4] = { 0.0f, 0.0f, 0.0f, 1.0f };
    d3dContext_->ClearRenderTargetView(backBufferTarget_, clearColor);
    d3dContext_->ClearDepthStencilView(depthView_, D3D11_CLEAR_DEPTH, 1.0f, 0);

    // GBuffer packing pass (in the future): /////////////////////////////////////////

    d3dContext_->OMSetRenderTargets(1, &backBufferTarget_, depthView_);

    unsigned int nStride = sizeof(Vertex);
    unsigned int nOffset = 0;

    d3dContext_->IASetInputLayout(inputLayout_);
    d3dContext_->IASetVertexBuffers(0, 1, &vertexBuffer_, &nStride, &nOffset);
    d3dContext_->IASetIndexBuffer(indexBuffer_, DXGI_FORMAT_R32_UINT, 0);
    d3dContext_->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

    d3dContext_->VSSetShader(firstVS_, 0, 0);
    d3dContext_->PSSetShader(firstPS_, 0, 0);

    d3dContext_->DrawIndexed(nIndexCount_, 0, 0);

    d3dContext_->OMSetRenderTargets(1, &backBufferTarget_, nullptr);

    d3dContext_->VSSetShader(secondVS_, 0, 0);
    d3dContext_->PSSetShader(secondPS_, 0, 0);
    d3dContext_->PSGetShaderResources(0, 1, &gbDepthView_);
    d3dContext_->PSSetSamplers(0, 1, &colorMapSampler_);

    d3dContext_->DrawIndexed(nIndexCount_, 0, 0);

    swapChain_->Present(0, 0);

In this temporary implementation, firstVS_ and secondVS_ are identical, and their only function is to do all the transforms and pass on the data to the PSs.

And finally, here are firstPS_ and secondPS_:

// firstPS_
float4 main(PS_Input frag) : SV_TARGET
{
    return float4(1.0f, 1.0f, 1.0f, 1.0f);
}

// secondPS_
Texture2D<float> depthMap_ : register(t0);
SamplerState colorSampler_ : register(s0);

float4 main(PS_Input frag) : SV_TARGET
{
    float4 psOut;
    psOut.xyz = depthMap_.Sample(colorSampler_, frag.tex0).xxx;
    psOut.w = 1.0f;
    return psOut;
}

So, my actual questions:

1) All this code compiles without any issues, but when I sample the depth buffer, it just turns out black. I read this could be caused by having your depth & stencil view bound by D3D11DeviceContext::OMSetRenderTargets() at the time you want to sample the depth buffer. I fixed that, but the buffer is still black. I checked the graphics debugger, with no success. So, is my depth buffer not getting written correctly, or am I sampling the wrong way? firstPS_ works fine.

2) Speaking of sampling, the book I'm using just says "we'll be using a point sampler," but I have no idea what is exactly meant. Now I'm just using a standard texture map sampler, but is there something else I should sample with?

3) Also, the book uses the SamplerState.Gather() function in secondPS_, but when I tried that it complained that "the expression could not be mapped to pixel shader instruction set." Is Gather() an error in the book, or is it my GPU (D3D feature level 11.0) who doesn't understand what that is? Is Sample() good enough for what I want to do? The original use of Gather() was in the context of creating a silhouette around objects in the depth buffer.

4) I tried to get secondVS_ to draw nothing but a full-screen quad, but FXC complained about my use of SV_VertexID as "invalid," saying that my type should be integral, even though it already was. I read somewhere that SV_VertexID can only be used by the first VS in a pipeline. Is that the problem here? How do I solve this in this particular case? In my current inefficient solution, is the problem being caused by the UVs?

Did you enabled the debug layer? Such errors like setting a resource as input as well as output are very easy to detect with the debug messages. Always my first step, if something returns unexpected black. — Gnietschow
The debug layer is on for sure, and all state creation warnings are #0. I still have no idea what's going wrong. — PeanutsGrowUnderground

Adam Miles Adam Miles · Accepted Answer · 2015-09-23T05:17:45

1) You've called PSGetShaderResources instead of PSSetShaderResources. Also, MostDetailedMip should be 0 not -1.

2) A "point sampler" is just a texture sampler with the FILTER field set to something like D3D11_FILTER_MIN_MAG_MIP_POINT.

3) Gather is a function on the Texture2D not the SamplerState as you stated.

4) You get this error if you compile using vs_4_0, try vs_5_0.

Problems sampling D3D11 depth buffer

1 Answers