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DX12 [DX12] (Solved) Depth buffer is rendering backwards?

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I can't for the life of me figure out why my depth buffer is playing up, and it seems like a simple oversight somewhere.


Basically, I'm drawing a series of objects in my scene and can navigate around. What happens is the objects are drawing as if they are behind each-other, with the farthest away objects being drawn through closer ones.


I can "solve" this by setting the depth buffer D3D12_CLEAR_VALUE to 0.0 and performing a D3D12_COMPARISON_FUNC_GREATER_EQUAL instead of D3D12_COMPARISON_FUNC_LESS_EQUAL Everything then renders correctly. However rather than being happy with that, I want to know what's causing this - as it's unusual and does not reflect the behaviour of the DirectX Samples.


My psuedo render loop:

  1. Set gbuffer as active render targets.

  2. Clear gbuffer render textures.

  3. Clear depth buffer.

  4. Draw objects.

  5. Set backbuffer as active render target.

  6. Draw gbuffer result.

In terms of actual code, I suppose the three useful bits here are my depth buffer creation, depth buffer clearing and PSO setup.


Creating the depth buffer:

// Create a resource description for the depth texture.
D3D12_RESOURCE_DESC depthDesc = {};
depthDesc.MipLevels = 1;
depthDesc.Format = DXGI_FORMAT_R32_TYPELESS;
depthDesc.Alignment = 0;
depthDesc.Width = _screenWidth;
depthDesc.Height = _screenHeight;
depthDesc.DepthOrArraySize = 1;
depthDesc.SampleDesc.Count = 1;
depthDesc.SampleDesc.Quality = 0;		
depthDesc.Layout = D3D12_TEXTURE_LAYOUT_UNKNOWN;

D3D12_CLEAR_VALUE* clearVal = new D3D12_CLEAR_VALUE();
clearVal->Format = DXGI_FORMAT_D32_FLOAT;
clearVal->DepthStencil.Depth = 1.0f;
clearVal->DepthStencil.Stencil = 0;

// Create a depth stencil view description.
D3D12_DEPTH_STENCIL_VIEW_DESC stencilDesc = {};
stencilDesc.Format = DXGI_FORMAT_D32_FLOAT;
stencilDesc.ViewDimension = D3D12_DSV_DIMENSION_TEXTURE2D;
stencilDesc.Texture2D.MipSlice = 0;

// Create a shader resource view description.
srvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
srvDesc.Format = DXGI_FORMAT_R32_FLOAT;
srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
srvDesc.Texture2D.MipLevels = 1;

LOGFAILEDCOM(_device->CreateCommittedResource(&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT), D3D12_HEAP_FLAG_NONE, &depthDesc, 
	D3D12_RESOURCE_STATE_DEPTH_READ, clearVal, IID_PPV_ARGS(&_pDepthBuffer)));
_device->CreateDepthStencilView(_pDepthBuffer, &stencilDesc, _dsvHeap->GetCPUDescriptorHandleForHeapStart());

DepthBufferIndex = ResourceFactory::GetTextureSlot();
CD3DX12_CPU_DESCRIPTOR_HANDLE srvHandle(_cbvSrvHeap->GetCPUDescriptorHandleForHeapStart(), DepthBufferIndex, D3DUtils::GetSRVDescriptorSize());
_device->CreateShaderResourceView(_pDepthBuffer, &srvDesc, srvHandle);

Clearing the depth buffer (how difficult can it be?):

_commandList->ClearDepthStencilView(_dsvHeap->GetCPUDescriptorHandleForHeapStart(), D3D12_CLEAR_FLAG_DEPTH, 1.0f, 0, 0, nullptr);

PSO (relevant bits):

psoDesc.InputLayout = {&inputLayout[0], UINT(inputLayout.size())};
psoDesc.pRootSignature = _pRootSignature;
psoDesc.VS = {reinterpret_cast<UINT8*>(_pVertexShader->GetBufferPointer()), _pVertexShader->GetBufferSize()};
psoDesc.PS = {reinterpret_cast<UINT8*>(_pPixelShader->GetBufferPointer()), _pPixelShader->GetBufferSize()};
psoDesc.RasterizerState = CD3DX12_RASTERIZER_DESC(D3D12_DEFAULT);
psoDesc.DSVFormat = DXGI_FORMAT_D32_FLOAT;
psoDesc.BlendState = blendState;
psoDesc.SampleMask = UINT_MAX;
psoDesc.SampleDesc.Count = 1;
psoDesc.PrimitiveTopologyType = D3D12_PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE;
psoDesc.DepthStencilState = CD3DX12_DEPTH_STENCIL_DESC(D3D12_DEFAULT);
psoDesc.DepthStencilState.DepthFunc = _depthCheck;
psoDesc.DepthStencilState.DepthEnable = TRUE;
psoDesc.DepthStencilState.StencilEnable = FALSE;
psoDesc.DepthStencilState.DepthWriteMask = _depthWrite;

psoDesc.NumRenderTargets = GBuffer::GBUFFER_NUM_TEXTURES;			
for (size_t i = 0; i < GBuffer::GBUFFER_NUM_TEXTURES; ++i)
	psoDesc.RTVFormats[i] = DXGI_FORMAT_R8G8B8A8_UNORM;
Edited by JJJohan

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How are you constructing your projection matrix? That sounds like the correct behavior for an inverted projection matrix (far and near plane swapped from traditional way).

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Ah, you're right. I overlooked my projection matrix!


I am beginning to recall reversing my projection matrix for the depth buffer accuracy for distant objects. It seems then that a clear value of 0 and reversing the depth functions is indeed correct behaviour.


I do feel silly now!

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