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Weird Observation with Depth/Stencil States


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#1 mhagain   Crossbones+   -  Reputation: 8005

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Posted 13 June 2012 - 04:44 PM

So, I'm creating a DepthStencil state to disable both depth testing and depth writing.

Setup is completely standard, and setting a breakpoint on the creation code confirms that the values are going in:
D3D11_DEPTH_STENCIL_DESC ddesc;

    ddesc.DepthEnable = FALSE;
    ddesc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ZERO;
Creation succeeds, but if I then do a GetDesc on the created state, I get the following:
ddesc.DepthEnable = FALSE;
    ddesc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ALL;
Also, if at runtime, I set the state, do GetDepthStencilState, then GetDesc, I also get the above - again with the D3D11_DEPTH_WRITE_MASK_ALL. PIX also tells me that it has D3D11_DEPTH_WRITE_MASK_ALL.

Running with AMD GPU Perf Studio confirms that writes to the depth buffer are happening, but this page - http://msdn.microsoft.com/en-us/library/windows/desktop/bb205120%28v=vs.85%29.aspx - indicates that this is not normal or expected behaviour - it should be answering "No" to "Is Depth Write enabled?" and earlying-out. Clearly it's not, and this is measurable as a quite significant performance decrease (did I mention that it's in a performance-sensitive part of the code - drawing fullscreen quads for post-processing filters).

What gives?

It appears that the gentleman thought C++ was extremely difficult and he was overjoyed that the machine was absorbing it; he understood that good C++ is difficult but the best C++ is well-nigh unintelligible.


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