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sepoto

Depth Buffer & Depth Stenciling.

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bool D3DClass::Initialize(int screenWidth, int screenHeight, bool vsync, HWND hwnd, bool fullscreen, float screenDepth, float screenNear)
{
	HRESULT result;
	IDXGIFactory* factory;
	IDXGIAdapter* adapter;
	IDXGIOutput* adapterOutput;
	unsigned int numModes, i, numerator, denominator, stringLength;
	DXGI_MODE_DESC* displayModeList;
	DXGI_ADAPTER_DESC adapterDesc;
	int error;
	DXGI_SWAP_CHAIN_DESC swapChainDesc;
	D3D_FEATURE_LEVEL featureLevel;
	ID3D11Texture2D* backBufferPtr;
	D3D11_TEXTURE2D_DESC depthBufferDesc;
	D3D11_DEPTH_STENCIL_DESC depthStencilDesc;
	D3D11_DEPTH_STENCIL_VIEW_DESC depthStencilViewDesc;
	D3D11_RASTERIZER_DESC rasterDesc;
	D3D11_VIEWPORT viewport;
	float fieldOfView, screenAspect;
	D3D11_DEPTH_STENCIL_DESC depthDisabledStencilDesc;


	// Store the vsync setting.
	m_vsync_enabled = vsync;

	// Create a DirectX graphics interface factory.
	result = CreateDXGIFactory(__uuidof(IDXGIFactory), (void**)&factory);
	if(FAILED(result))
	{
		return false;
	}

	// Use the factory to create an adapter for the primary graphics interface (video card).
	result = factory->EnumAdapters(0, &adapter);
	if(FAILED(result))
	{
		return false;
	}

	// Enumerate the primary adapter output (monitor).
	result = adapter->EnumOutputs(0, &adapterOutput);
	if(FAILED(result))
	{
		return false;
	}

	// Get the number of modes that fit the DXGI_FORMAT_R8G8B8A8_UNORM display format for the adapter output (monitor).
	result = adapterOutput->GetDisplayModeList(DXGI_FORMAT_R8G8B8A8_UNORM, DXGI_ENUM_MODES_INTERLACED, &numModes, NULL);
	if(FAILED(result))
	{
		return false;
	}

	// Create a list to hold all the possible display modes for this monitor/video card combination.
	displayModeList = new DXGI_MODE_DESC[numModes];
	if(!displayModeList)
	{
		return false;
	}

	// Now fill the display mode list structures.
	result = adapterOutput->GetDisplayModeList(DXGI_FORMAT_R8G8B8A8_UNORM, DXGI_ENUM_MODES_INTERLACED, &numModes, displayModeList);
	if(FAILED(result))
	{
		return false;
	}

	// Now go through all the display modes and find the one that matches the screen width and height.
	// When a match is found store the numerator and denominator of the refresh rate for that monitor.
	for(i=0; i<numModes; i++)
	{
		if(displayModeList[i].Width == (unsigned int)screenWidth)
		{
			if(displayModeList[i].Height == (unsigned int)screenHeight)
			{
				numerator = displayModeList[i].RefreshRate.Numerator;
				denominator = displayModeList[i].RefreshRate.Denominator;
			}
		}
	}

	// Get the adapter (video card) description.
	result = adapter->GetDesc(&adapterDesc);
	if(FAILED(result))
	{
		return false;
	}

	// Store the dedicated video card memory in megabytes.
	m_videoCardMemory = (int)(adapterDesc.DedicatedVideoMemory / 1024 / 1024);

	// Convert the name of the video card to a character array and store it.
	error = wcstombs_s(&stringLength, m_videoCardDescription, 128, adapterDesc.Description, 128);
	if(error != 0)
	{
		return false;
	}

	// Release the display mode list.
	delete [] displayModeList;
	displayModeList = 0;

	// Release the adapter output.
	adapterOutput->Release();
	adapterOutput = 0;

	// Release the adapter.
	adapter->Release();
	adapter = 0;

	// Release the factory.
	factory->Release();
	factory = 0;

	// Initialize the swap chain description.
    ZeroMemory(&swapChainDesc, sizeof(swapChainDesc));

	// Set to a single back buffer.
    swapChainDesc.BufferCount = 1;

	// Set the width and height of the back buffer.
    swapChainDesc.BufferDesc.Width = screenWidth;
    swapChainDesc.BufferDesc.Height = screenHeight;

	// Set regular 32-bit surface for the back buffer.
    swapChainDesc.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;

	// Set the refresh rate of the back buffer.
	if(m_vsync_enabled)
	{
	    swapChainDesc.BufferDesc.RefreshRate.Numerator = numerator;
		swapChainDesc.BufferDesc.RefreshRate.Denominator = denominator;
	}
	else
	{
	    swapChainDesc.BufferDesc.RefreshRate.Numerator = 0;
		swapChainDesc.BufferDesc.RefreshRate.Denominator = 1;
	}

	// Set the usage of the back buffer.
    swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;

	// Set the handle for the window to render to.
    swapChainDesc.OutputWindow = hwnd;

	// Turn multisampling off.
    swapChainDesc.SampleDesc.Count = 1;
    swapChainDesc.SampleDesc.Quality = 0;

	// Set to full screen or windowed mode.
	if(fullscreen)
	{
		swapChainDesc.Windowed = false;
	}
	else
	{
		swapChainDesc.Windowed = true;
	}

	// Set the scan line ordering and scaling to unspecified.
	swapChainDesc.BufferDesc.ScanlineOrdering = DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
	swapChainDesc.BufferDesc.Scaling = DXGI_MODE_SCALING_UNSPECIFIED;

	// Discard the back buffer contents after presenting.
	swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;

	// Don't set the advanced flags.
	swapChainDesc.Flags = 0;

	// Set the feature level to DirectX 11.
	featureLevel = D3D_FEATURE_LEVEL_11_0;

	// Create the swap chain, Direct3D device, and Direct3D device context.
	result = D3D11CreateDeviceAndSwapChain(NULL, D3D_DRIVER_TYPE_HARDWARE, NULL, 0, &featureLevel, 1, D3D11_SDK_VERSION, &swapChainDesc, &m_swapChain, 
										   &m_device, NULL, &m_deviceContext);
	if(FAILED(result))
	{
		return false;
	}

	// Get the pointer to the back buffer.
	result = m_swapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), (LPVOID*)&backBufferPtr);
	if(FAILED(result))
	{
		return false;
	}

	// Create the render target view with the back buffer pointer.
	result = m_device->CreateRenderTargetView(backBufferPtr, NULL, &m_renderTargetView);
	if(FAILED(result))
	{
		return false;
	}

	// Release pointer to the back buffer as we no longer need it.
	backBufferPtr->Release();
	backBufferPtr = 0;

	// Initialize the description of the depth buffer.
	ZeroMemory(&depthBufferDesc, sizeof(depthBufferDesc));

	// Set up the description of the depth buffer.
	depthBufferDesc.Width = screenWidth;
	depthBufferDesc.Height = screenHeight;
	depthBufferDesc.MipLevels = 1;
	depthBufferDesc.ArraySize = 1;
	depthBufferDesc.Format = DXGI_FORMAT_D24_UNORM_S8_UINT;
	depthBufferDesc.SampleDesc.Count = 1;
	depthBufferDesc.SampleDesc.Quality = 0;
	depthBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	depthBufferDesc.BindFlags = D3D11_BIND_DEPTH_STENCIL;
	depthBufferDesc.CPUAccessFlags = 0;
	depthBufferDesc.MiscFlags = 0;

	// Create the texture for the depth buffer using the filled out description.
	result = m_device->CreateTexture2D(&depthBufferDesc, NULL, &m_depthStencilBuffer);
	if(FAILED(result))
	{
		return false;
	}

	// Initialize the description of the stencil state.
	ZeroMemory(&depthStencilDesc, sizeof(depthStencilDesc));

	// Set up the description of the stencil state.
	depthStencilDesc.DepthEnable = true;
	depthStencilDesc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ALL;
	depthStencilDesc.DepthFunc = D3D11_COMPARISON_LESS;

	depthStencilDesc.StencilEnable = true;
	depthStencilDesc.StencilReadMask = 0xFF;
	depthStencilDesc.StencilWriteMask = 0xFF;

	// Stencil operations if pixel is front-facing.
	depthStencilDesc.FrontFace.StencilFailOp = D3D11_STENCIL_OP_KEEP;
	depthStencilDesc.FrontFace.StencilDepthFailOp = D3D11_STENCIL_OP_INCR;
	depthStencilDesc.FrontFace.StencilPassOp = D3D11_STENCIL_OP_KEEP;
	depthStencilDesc.FrontFace.StencilFunc = D3D11_COMPARISON_ALWAYS;

	// Stencil operations if pixel is back-facing.
	depthStencilDesc.BackFace.StencilFailOp = D3D11_STENCIL_OP_KEEP;
	depthStencilDesc.BackFace.StencilDepthFailOp = D3D11_STENCIL_OP_DECR;
	depthStencilDesc.BackFace.StencilPassOp = D3D11_STENCIL_OP_KEEP;
	depthStencilDesc.BackFace.StencilFunc = D3D11_COMPARISON_ALWAYS;

	// Create the depth stencil state.
	result = m_device->CreateDepthStencilState(&depthStencilDesc, &m_depthStencilState);
	if(FAILED(result))
	{
		return false;
	}

	// Set the depth stencil state.
	m_deviceContext->OMSetDepthStencilState(m_depthStencilState, 1);

	// Initialize the depth stencil view.
	ZeroMemory(&depthStencilViewDesc, sizeof(depthStencilViewDesc));

	// Set up the depth stencil view description.
	depthStencilViewDesc.Format = DXGI_FORMAT_D24_UNORM_S8_UINT;
	depthStencilViewDesc.ViewDimension = D3D11_DSV_DIMENSION_TEXTURE2D;
	depthStencilViewDesc.Texture2D.MipSlice = 0;

	// Create the depth stencil view.
	result = m_device->CreateDepthStencilView(m_depthStencilBuffer, &depthStencilViewDesc, &m_depthStencilView);
	if(FAILED(result))
	{
		return false;
	}

	// Bind the render target view and depth stencil buffer to the output render pipeline.
	m_deviceContext->OMSetRenderTargets(1, &m_renderTargetView, m_depthStencilView);

	// Setup the raster description which will determine how and what polygons will be drawn.
	rasterDesc.AntialiasedLineEnable = false;
	rasterDesc.CullMode = D3D11_CULL_BACK;
	rasterDesc.DepthBias = 0;
	rasterDesc.DepthBiasClamp = 0.0f;
	rasterDesc.DepthClipEnable = true;
	rasterDesc.FillMode = D3D11_FILL_SOLID;
	rasterDesc.FrontCounterClockwise = false;
	rasterDesc.MultisampleEnable = false;
	rasterDesc.ScissorEnable = false;
	rasterDesc.SlopeScaledDepthBias = 0.0f;

	// Create the rasterizer state from the description we just filled out.
	result = m_device->CreateRasterizerState(&rasterDesc, &m_rasterState);
	if(FAILED(result))
	{
		return false;
	}

	// Now set the rasterizer state.
	m_deviceContext->RSSetState(m_rasterState);
	
	// Setup the viewport for rendering.
    viewport.Width = (float)screenWidth;
    viewport.Height = (float)screenHeight;
    viewport.MinDepth = 0.0f;
    viewport.MaxDepth = 1.0f;
    viewport.TopLeftX = 0.0f;
    viewport.TopLeftY = 0.0f;

	// Create the viewport.
    m_deviceContext->RSSetViewports(1, &viewport);

	// Setup the projection matrix.
	fieldOfView = (float)D3DX_PI / 4.0f;
	screenAspect = (float)screenWidth / (float)screenHeight;

	// Create the projection matrix for 3D rendering.
	D3DXMatrixPerspectiveFovLH(&m_projectionMatrix, fieldOfView, screenAspect, screenNear, screenDepth);

    // Initialize the world matrix to the identity matrix.
    D3DXMatrixIdentity(&m_worldMatrix);

	// Create an orthographic projection matrix for 2D rendering.
	D3DXMatrixOrthoLH(&m_orthoMatrix, (float)screenWidth, (float)screenHeight, screenNear, screenDepth);

	// Clear the second depth stencil state before setting the parameters.
	ZeroMemory(&depthDisabledStencilDesc, sizeof(depthDisabledStencilDesc));

	// Now create a second depth stencil state which turns off the Z buffer for 2D rendering.  The only difference is 
	// that DepthEnable is set to false, all other parameters are the same as the other depth stencil state.
	depthDisabledStencilDesc.DepthEnable = false;
	depthDisabledStencilDesc.DepthWriteMask = D3D11_DEPTH_WRITE_MASK_ALL;
	depthDisabledStencilDesc.DepthFunc = D3D11_COMPARISON_LESS;
	depthDisabledStencilDesc.StencilEnable = true;
	depthDisabledStencilDesc.StencilReadMask = 0xFF;
	depthDisabledStencilDesc.StencilWriteMask = 0xFF;
	depthDisabledStencilDesc.FrontFace.StencilFailOp = D3D11_STENCIL_OP_KEEP;
	depthDisabledStencilDesc.FrontFace.StencilDepthFailOp = D3D11_STENCIL_OP_INCR;
	depthDisabledStencilDesc.FrontFace.StencilPassOp = D3D11_STENCIL_OP_KEEP;
	depthDisabledStencilDesc.FrontFace.StencilFunc = D3D11_COMPARISON_ALWAYS;
	depthDisabledStencilDesc.BackFace.StencilFailOp = D3D11_STENCIL_OP_KEEP;
	depthDisabledStencilDesc.BackFace.StencilDepthFailOp = D3D11_STENCIL_OP_DECR;
	depthDisabledStencilDesc.BackFace.StencilPassOp = D3D11_STENCIL_OP_KEEP;
	depthDisabledStencilDesc.BackFace.StencilFunc = D3D11_COMPARISON_ALWAYS;

	// Create the state using the device.
	result = m_device->CreateDepthStencilState(&depthDisabledStencilDesc, &m_depthDisabledStencilState);
	if(FAILED(result))
	{
		return false;
	}

    return true;
}

If I understand correctly after the number of adapters on the machine are enumerated and the settings of the target video adapter are stored there is a swap chain that is created. The swap chain is given a format of DXGI_FORMAT_R8G8B8A8_UNORM. As far as I can ascertain that means to create the back buffer I think with a 32-bit color scheme. I found very little documentation describing what DXGI_FORMAT_R8G8B8A8_UNORM actually means.

 

The usage of the back buffer is set:

// Set the usage of the back buffer.
    swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
 
If I understand correctly that means that a render target view is going to be set up. When the render target view is rendered to the buffers should be swapped effectively displaying what was rendered to the render target view.
 
 
	// Initialize the description of the depth buffer.
	ZeroMemory(&depthBufferDesc, sizeof(depthBufferDesc));

	// Set up the description of the depth buffer.
	depthBufferDesc.Width = screenWidth;
	depthBufferDesc.Height = screenHeight;
	depthBufferDesc.MipLevels = 1;
	depthBufferDesc.ArraySize = 1;
	depthBufferDesc.Format = DXGI_FORMAT_D24_UNORM_S8_UINT;
	depthBufferDesc.SampleDesc.Count = 1;
	depthBufferDesc.SampleDesc.Quality = 0;
	depthBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	depthBufferDesc.BindFlags = D3D11_BIND_DEPTH_STENCIL;
	depthBufferDesc.CPUAccessFlags = 0;
	depthBufferDesc.MiscFlags = 0;

	// Create the texture for the depth buffer using the filled out description.
	result = m_device->CreateTexture2D(&depthBufferDesc, NULL, &m_depthStencilBuffer);
	if(FAILED(result))
	{
		return false;
	}

This code is from the rastertek.com Tutorial 11 sample on setting up an orthographic projection.

 

If I understand correctly a depth buffer is being described and a depth buffer is the same height and width of the back buffer. If I understand correctly the buffers in the swap chain and the depth buffer are essentially textures the contain rendered pixel data.

 

The format DXGI_FORMAT_D24_UNORM_S8_UINT is different than the format used to create the swap chain? Why is there a difference in format?

 

I take D3D11_BIND_DEPTH_STENCIL to mean that the depth buffer is going to be bound in some way to a depth stencil. What is the difference between a depth buffer and a depth stencil? I see there is also a depth stencil view. What is the purpose of the depth stencil view? 

 

What is the purpose of the binding here:

m_deviceContext->OMSetRenderTargets(1, &m_renderTargetView, m_depthStencilView);

 

 

Thanks for any help on these questions!

 
 
 
I have been going through again the tutorial. It seems the main idea is that the Z buffer can be enabled or disabled for 2D drawing. The lines I am curious about are not really described in the tutorial although there are good comments and I see now that depthEnable is the important property as far as enabling and disabling 2D drawing. As well the matrix projectionMatrix has to be supplanted with orthoMatrix.
Edited by sepoto
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