Wrong depth buffer (to texture) output?

Question

For the SSAO effect I have to generate two textures: normals (in view space) and depth.

I decided to use depth buffer as texture according to Microsoft tutorial (the Reading the Depth-Stencil Buffer as a Texture chapter).

Unfortunately, after rendering I got none information from the depth buffer (the lower image):

I guess it's not right. And what is strange, the depth buffer seems to work (I get the right order of faces etc.).

The depth buffer code:

//create depth stencil texture (depth buffer)
D3D11_TEXTURE2D_DESC descDepth;
ZeroMemory(&descDepth, sizeof(descDepth));
descDepth.Width = width;
descDepth.Height = height;
descDepth.MipLevels = 1;
descDepth.ArraySize = 1;
descDepth.Format = DXGI_FORMAT_R24G8_TYPELESS;
descDepth.SampleDesc.Count = antiAliasing.getCount();
descDepth.SampleDesc.Quality = antiAliasing.getQuality();
descDepth.Usage = D3D11_USAGE_DEFAULT;
descDepth.BindFlags = D3D11_BIND_DEPTH_STENCIL | D3D11_BIND_SHADER_RESOURCE;
descDepth.CPUAccessFlags = 0;
descDepth.MiscFlags = 0;

ID3D11Texture2D* depthStencil = NULL;
result = device->CreateTexture2D(&descDepth, NULL, &depthStencil);
ERROR_HANDLE(SUCCEEDED(result), L"Could not create depth stencil texture.", MOD_GRAPHIC);

D3D11_SHADER_RESOURCE_VIEW_DESC shaderResourceViewDesc;
//setup the description of the shader resource view
shaderResourceViewDesc.Format = DXGI_FORMAT_R24_UNORM_X8_TYPELESS;
shaderResourceViewDesc.ViewDimension = antiAliasing.isOn() ? D3D11_SRV_DIMENSION_TEXTURE2DMS : D3D11_SRV_DIMENSION_TEXTURE2D;
shaderResourceViewDesc.Texture2D.MostDetailedMip = 0;
shaderResourceViewDesc.Texture2D.MipLevels = 1;

//create the shader resource view.
ERROR_HANDLE(SUCCEEDED(device->CreateShaderResourceView(depthStencil, &shaderResourceViewDesc, &depthStencilShaderResourceView)),
    L"Could not create shader resource view for depth buffer.", MOD_GRAPHIC);

createDepthStencilStates();
//set the depth stencil state.
context->OMSetDepthStencilState(depthStencilState3D, 1);

D3D11_DEPTH_STENCIL_VIEW_DESC depthStencilViewDesc;
// Initialize the depth stencil view.
ZeroMemory(&depthStencilViewDesc, sizeof(depthStencilViewDesc));

// Set up the depth stencil view description.
depthStencilViewDesc.Format = DXGI_FORMAT_D24_UNORM_S8_UINT;
depthStencilViewDesc.ViewDimension = antiAliasing.isOn() ? D3D11_DSV_DIMENSION_TEXTURE2DMS : D3D11_DSV_DIMENSION_TEXTURE2D;
depthStencilViewDesc.Texture2D.MipSlice = 0;
//depthStencilViewDesc.Flags = D3D11_DSV_READ_ONLY_DEPTH;

// Create the depth stencil view.
result = device->CreateDepthStencilView(depthStencil, &depthStencilViewDesc, &depthStencilView);
ERROR_HANDLE(SUCCEEDED(result), L"Could not create depth stencil view.", MOD_GRAPHIC);

After rendering with first pass, I set the depth stencil as texture resource along with other render targets (color, normals), appending it to array:

ID3D11ShaderResourceView ** textures = new ID3D11ShaderResourceView *[targets.size()+1];
for (unsigned i = 0; i < targets.size(); i++) {
    textures[i] = targets[i]->getShaderResourceView();
}
textures[targets.size()] = depthStencilShaderResourceView;
context->PSSetShaderResources(0, targets.size()+1, textures);

Before second pass I call context->OMSetRenderTargets(1, &myRenderTargetView, NULL); to unbind depth buffer (so I can use it as texture).

Then, I render my textures (render targets from first pass + depth buffer) with trivial post-process shader, just for debug purpose (second pass):

Texture2D ColorTexture[3];
SamplerState ObjSamplerState;

float4 main(VS_OUTPUT input) : SV_TARGET0{
    float4 Color;
    Color = float4(0, 1, 1, 1);
    float2 textureCoordinates = input.textureCoordinates.xy * 2;
    if (input.textureCoordinates.x < 0.5f && input.textureCoordinates.y < 0.5f) {
        Color = ColorTexture[0].Sample(ObjSamplerState, textureCoordinates);
    }
    if (input.textureCoordinates.x > 0.5f && input.textureCoordinates.y < 0.5f) {
        textureCoordinates.x -= 0.5f;
        Color = ColorTexture[1].Sample(ObjSamplerState, textureCoordinates);
    }
    if (input.textureCoordinates.x < 0.5f && input.textureCoordinates.y > 0.5f) { //depth texture
        textureCoordinates.y -= 0.5f;
        Color = ColorTexture[2].Sample(ObjSamplerState, textureCoordinates);
    }
...

It works fine for normals texture. Why it doesn't for depth buffer (as shader resource view)?

Answer 1

As per comments:

The texture was rendered and sampled correctly but the data appeared to be uniformly red due to the data lying between 0.999 and 1.0f.

There are a few things you can do to improve the available depth precision, but the simplest of which is to simply ensure your near and far clip distances are not excessively small/large for the scene you're drawing.

Assuming metres are your unit, a near clip of 0.1 (10cm) and a far clip of 200 (metres) are much more reasonable than 1cm and 20km.

Even so, don't expect to see too many black/dark areas, the non linear nature of a z-buffer is still going to mean most of your depth values are shunted up towards 1. If visualisation of the depth buffer is important then simply rescale the data to the normalised 0-1 range before displaying it.