How to print Depth to a Texture2D and then read it in the next pass on a shader in DirectX11

Question

I'm programming a two-pass effect in DirectX 11 (SharpDX). It's supposed to write the depth to a texture in the first pass and then use that texture to extract data on the second one in the pixel shader.

What I get is a white screen, with nothing but the interface and I don't know why nothing is being printed. What could be the problem? I would say I should get at least something from the Depth Texture.

This is how I'm setting the depth texture values:

this.depthBuffer = new Texture2D(device, new Texture2DDescription()
        {
            Format = Format.R32_Typeless,
            ArraySize = 1,
            MipLevels = 1,
            Width = (int)host.ActualWidth,
            Height = (int)host.ActualHeight,
            SampleDescription = new SampleDescription(1, 0),
            Usage = ResourceUsage.Default,
            BindFlags = BindFlags.DepthStencil | BindFlags.ShaderResource,
            CpuAccessFlags = CpuAccessFlags.None,
            OptionFlags = ResourceOptionFlags.None,
        });

this.depthBufferShaderResourceView = new ShaderResourceView(this.device, this.depthBuffer, new ShaderResourceViewDescription()
        {
            Format = Format.R32_Float,
            Dimension = ShaderResourceViewDimension.Texture2D,
            Texture2D = new ShaderResourceViewDescription.Texture2DResource()
            {
                MipLevels = 1,
                MostDetailedMip = 0,
            }
        });
var depthStencilDesc = new DepthStencilStateDescription()
        {
            DepthComparison = Comparison.LessEqual,
            DepthWriteMask = global::SharpDX.Direct3D11.DepthWriteMask.All,
            IsDepthEnabled = true,
        };

And here is how I sample the depth in the .fx file:

int3 posTex = int3(input.p.xy, 0);
float depthPixel = DepthTexture.Load(posTex);
float4 color = float4(depthPixel, depthPixel , depthPixel, 1.0f );
return color;

And here the way I'm now setting the Depth Buffer stencil view as a Render Target in 2 passes. In the first I try to set the depthstencilview as a target. In the second pass I'm trying to set teh depth texture as a shader resource to read from it.

this.device.ImmediateContext.InputAssembler.SetVertexBuffers(0, new VertexBufferBinding(this.vertexBuffer, LinesVertex.SizeInBytes, 0));

// PASS 0
this.device.ImmediateContext.OutputMerger.SetTargets(depthBufferStencilView);
this.device.ImmediateContext.ClearDepthStencilView(this.depthBufferStencilView,     DepthStencilClearFlags.Depth | DepthStencilClearFlags.Stencil, 1.0f, 0);
this.technique.GetPassByIndex(0).Apply(this.device.ImmediateContext);
this.device.ImmediateContext.DrawIndexed(this.geometry.Indices.Length, 0, 0);

// PASS 1
this.device.ImmediateContext.OutputMerger.ResetTargets(); // unbinding the depthStencilView

this.device.ImmediateContext.InputAssembler.SetVertexBuffers(0, new VertexBufferBinding(this.vertexBuffer, LinesVertex.SizeInBytes, 0));
this.depthStencilShaderResourceVariable = effect.GetVariableByName("DepthTexture").AsShaderResource();
this.depthStencilShaderResourceVariable.SetResource(this.depthBufferShaderResourceView);
this.technique.GetPassByIndex(1).Apply(this.device.ImmediateContext);
this.device.ImmediateContext.DrawIndexed(this.geometry.Indices.Length, 0, 0);

Finally, this is how I set the two passes in the .fx file:

technique11 RenderMyTechnique
{
pass P0
{   

SetDepthStencilState( DSSDepthLessEqual, 0 );
SetVertexShader     ( CompileShader( vs_4_0, VShader() ) );
    SetHullShader       ( NULL );
    SetDomainShader     ( NULL );        
    SetGeometryShader   ( NULL  );
SetPixelShader      ( NULL );
}

pass P1
{
SetDepthStencilState( DSSDepthLessEqual, 0 );
SetVertexShader     ( CompileShader( vs_4_0, VShader() ) );
    SetHullShader       ( NULL );
    SetDomainShader     ( NULL );        
    SetGeometryShader   ( CompileShader( gs_4_0, GShader() ) );
SetPixelShader      ( CompileShader( ps_4_0, PShader() ) );
}
}

Answer 1

My guess would be that you've bound the texture for reading and writing at the same time (i.e. it's the current depth buffer). DX11 won't let you do that (the debug runtime should give you an error message about it).

Also note that it decides what the current depth buffer is at the time you bind the shader resource, and not at draw call time so you want to bind the correct set of render targets before binding any shader resources.

There are three solutions:

1. Unbind the depth buffer while reading from it in a shader. This assumes you don't need depth testing.
2. Copy the depth buffer at some point, and read from the copy. This is clearly the slowest option.
3. Bind the depth buffer as read only. This won't work on 10.0 or 10.1 hardware.