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).

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.

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.