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Writing to the Stencil Buffer


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#1 CppPerson   Members   -  Reputation: 163

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Posted 06 February 2013 - 09:57 AM

Hi guys,

 

is there any way in standard D3D11 to write values directly to the stencil buffer, for use in another pass? What I want to do is:

 

  • Have a screen-space shader that reads a bunch of inputs and generates an 8-bit texture.
  • Copy this 8-bit texture into a depth-stencil texture in the stencil channel.
  • Use that depth-stencil to mask further drawing.

 

I can think of a couple different ways of achieving the same goal without doing this but they all require excessive bandwidth, e.g:

 

  • Run a screen-space pass for each stencil value (0-255), reading inputs and discarding pixels that don't match with a clip.
  • Output a single, fixed stencil value for each pass.
  • Use this as the mask.

 

On each of those 255 passes I'm going to be reading the inputs repeatedly and that's not great.

 

I know D3D11 doesn't have an equivalent of ARB_shader_stencil_export so I was hoping there'd be some way of using typeless formats to achieve this, but so far my testing hasn't revealed anything (e.g. can't bind typeless formats as render targets).



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#2 Yourself   Crossbones+   -  Reputation: 1189

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Posted 06 February 2013 - 01:52 PM

What you could try (I haven't tried it myself but I think it will work), is using a compute shader.

Create an UAV from the depth/stencil texture and write to the stencil channel.

 



#3 CppPerson   Members   -  Reputation: 163

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Posted 08 February 2013 - 06:08 AM

Thanks for the idea but this doesn't seem to work.

 

My first attempt was to use D3D11_BIND_DEPTH_STENCIL on the depth/stencil texture but this gives:

 


D3D11: ERROR: ID3D11Device::CreateTexture2D:
       The BindFlags D3D11_BIND_UNORDERED_ACCESS and D3D11_BIND_DEPTH_STENCIL can't both be specified.
       [ STATE_CREATION ERROR #99: CREATETEXTURE2D_INVALIDBINDFLAGS ]
 
D3D11: ERROR: ID3D11Device::CreateTexture2D:
       The format (0x2d, D24_UNORM_S8_UINT) cannot be bound as an UnorderedAccessView, or cast to a format that could be bound as an UnorderedAccessView.
       Therefore this format does not support D3D11_BIND_UNORDERED_ACCESS.
       [ STATE_CREATION ERROR #92: CREATETEXTURE2D_UNSUPPORTEDFORMAT ]

In the vein hope that the last message might have been inaccurate, I also tried creating a DXGI_FORMAT_X24_TYPELESS_G8_UINT texture to that I could at least Resolve to a D24S8:

 

 D3D11: ERROR: ID3D11Device::CreateTexture2D:
       The format (0x2f, X24_TYPELESS_G8_UINT) cannot be bound as an UnorderedAccessView, or cast to a format that could be bound as an UnorderedAccessView.
       Therefore this format does not support D3D11_BIND_UNORDERED_ACCESS. [ STATE_CREATION ERROR #92: CREATETEXTURE2D_UNSUPPORTEDFORMAT ]

 

So it looks like this is not possible! Which is really confusing, because I can do this on an 8 year old console, but not the latest, expensive gaming PC. sad.png





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