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c++visual-studio-debuggingdirectx-11deferred-rendering

Deferred Rendering: Performance issues

I've just implemented deferred rendering/shading for the first time and I was surprised to see the big perfomance gap between forward and deferred rendering.

When I run my application with forward rendering I get a pretty decent frame rate while running in Release mode

FORWARD RENDERING enter image description here

However when I ran it with deferred rendering it gave me a rather surprising output

DEFERRED RENDERING enter image description here

I'm well aware of that deferred rendering is NOT something you coat an application with to make it go "faster". I consider it to be a performance optimization technique that can be optimized in a numerous ways and I understand that the technique has a larger memory footprint than forward rendering.

However...

I've currently got ONE point light in the scene and one hundred cubes created with hardware instancing. The light is moving back and forth on the Z-axis casting light on the cubes.

The problem is that the light is very laggy when moving. It's so laggy that the application doesn't register the keyboard input. Honestly, I was not prepared for this and I assume that I'm doing something terrible bad in my implementation.

So far I've changed the texture format on the gbuffers from DXGI_FORMAT_R32G32B32A32_FLOAT to DXGI_FORMAT_R16G16B16A16_FLOAT jsut to see if it had any visual impact but it did not.

Any suggestions? Thank you!

SIDE NOTE
I'm using the Visual Studio Graphics Diagnostics for debugging my DirectX applications

Solution

  • Solved it!

    I enabled the DirectX debug layer and I got a sea of D3D11 warnings

    D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets: Resource being set to OM RenderTarget slot 1 is still bound on input! [ STATE_SETTING WARNING #9: DEVICE_OMSETRENDERTARGETS_HAZARD]
D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets[AndUnorderedAccessViews]: Forcing PS shader resource slot 1 to NULL. [ STATE_SETTING WARNING #7: DEVICE_PSSETSHADERRESOURCES_HAZARD]
D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets: Resource being set to OM RenderTarget slot 2 is still bound on input! [ STATE_SETTING WARNING #9: DEVICE_OMSETRENDERTARGETS_HAZARD]
D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets[AndUnorderedAccessViews]: Forcing PS shader resource slot 2 to NULL. [ STATE_SETTING WARNING #7: DEVICE_PSSETSHADERRESOURCES_HAZARD]
D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets: Resource being set to OM RenderTarget slot 3 is still bound on input! [ STATE_SETTING WARNING #9: DEVICE_OMSETRENDERTARGETS_HAZARD]
D3D11 WARNING: ID3D11DeviceContext::OMSetRenderTargets[AndUnorderedAccessViews]: Forcing PS shader resource slot 3 to NULL. [ STATE_SETTING WARNING #7: DEVICE_PSSETSHADERRESOURCES_HAZARD]

    So at the end of the render function i.e. after

    mSwapChain->Present( 0, 0 );

    I added

    mDeviceContext->ClearState();

    Just to reset the device context which sets all input/output resource slots to NULL as explained on MSDN