####Indices####
As you know, a triangle is defined by 3 vertices. In the previous tutorial, we had a vertex buffer containing 3 vertices, and drew a triangle by calling DrawInstanced(), telling it to draw 3 vertices. Now we want to draw a quad. A quad is 2 triangles. Does that mean we now need 6 vertices to draw this triangle? 2 of the vertices are actually duplicates, so it is a waste to keep these extra vertices in memory, as well as a slight performance loss passing the duplicate vertices to the GPU.

To remove these duplicate vertices, we can define our geometry with an index buffer. An index buffer is a list of indexes. Each index represents a vertex. Every 3 indices represents a triangle. 

So now instead of defining our quad's vertex buffer with 6 vertices:
    Vertex vList[] = {
    // first triangle
	{ -0.5f,  0.5f, 0.5f }, // top left
	{  0.5f, -0.5f, 0.5f }, // bottom right
	{ -0.5f, -0.5f, 0.5f }, // bottom left
    
    // second triangle
	{ -0.5f,  0.5f, 0.5f }, // top left
	{  0.5f,  0.5f, 0.5f }, // top right
	{  0.5f, -0.5f, 0.5f }  // bottom right
    };
    
We can define it with 4:
    Vertex vList[] = {
	{ -0.5f,  0.5f, 0.5f }, // top left
	{  0.5f, -0.5f, 0.5f }, // bottom right
	{ -0.5f, -0.5f, 0.5f }, // bottom left
	{  0.5f,  0.5f, 0.5f }  // top right
    };

And provide an index buffer that defines the two triangles that make up our quad:
    DWORD iList[] = {
	0, 1, 2, // first triangle
	0, 3, 1 // second triangle
    };

Duplicate vertices are vertices that are exactly the same, including all attributes such as color, texture coordinates and position. In this example we have two duplicate vertices because two of the vertices share the same position and color. Later when we draw a textured cube, you may thing we only need 8 vertices because a cube only has 8 corners. We will actually need 24 (4 vertices for each side of the cube, a cube has 6 sides). The reason is because even though the position of the 8 corners are shared between 3 different faces, each face's vertex in that corner will have a different texture coordinate. Just thought I would try to be as clear as possible about that because i have seen way too often people trying to create cubes and geometry by removing all vertices with duplicate positions, even when some of the "duplicate" vertices were not duplicates at all, they had different texture coordinates or normal coordinates for example.

Let's get to the code

####Globals####
We have two new variables. The first new variable is our index buffer, which will be a default heap. The second is an index buffer view so that we have a pointer to our index buffer, the format of the indices, and the size of the buffer.

	ID3D12Resource* indexBuffer; // a default buffer in GPU memory that we will load index data for our triangle into
    
	D3D12_INDEX_BUFFER_VIEW indexBufferView; // a structure holding information about the index buffer

####Adding to the vertex buffer####
We will be drawing a quad in this tutorial. A quad is 2 triangles. Since we are using an index buffer, we do not have to duplicate any vertices for the quad, which means we only need 4 vertices, one for each corner of the quad.

	Vertex vList[] = {
		{ -0.5f,  0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f },
		{  0.5f, -0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f },
		{ -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f },
		{  0.5f,  0.5f, 0.5f, 1.0f, 0.0f, 1.0f, 1.0f }
	};

####Creating the index buffer####
We will be creating the index buffer and uploading it to the GPU exactly the same way we did for the vertex buffer.

First we define the index buffer, then we create two resource heaps, one upload and one default.

After we have created the resource heaps, we upload the index buffer by copying the the index buffer from the upload heap to the default heap.

When we have uploaded the index buffer, we can obtain a pointer to the GPU memory address of the index buffer, and store it in our indexBufferView.

	// Create index buffer
    
	// a quad (2 triangles)
	DWORD iList[] = {
		0, 1, 2, // first triangle
		0, 3, 1 // second triangle
	};
	
	int iBufferSize = sizeof(iList);
	
	// create default heap to hold index buffer
	device->CreateCommittedResource(
		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT), // a default heap
		D3D12_HEAP_FLAG_NONE, // no flags
		&CD3DX12_RESOURCE_DESC::Buffer(iBufferSize), // resource description for a buffer
		D3D12_RESOURCE_STATE_COPY_DEST, // start in the copy destination state
		nullptr, // optimized clear value must be null for this type of resource
		IID_PPV_ARGS(&indexBuffer));
	
	// we can give resource heaps a name so when we debug with the graphics debugger we know what resource we are looking at
	vertexBuffer->SetName(L"Index Buffer Resource Heap");
	
	// create upload heap to upload index buffer
	ID3D12Resource* iBufferUploadHeap;
	device->CreateCommittedResource(
		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_UPLOAD), // upload heap
		D3D12_HEAP_FLAG_NONE, // no flags
		&CD3DX12_RESOURCE_DESC::Buffer(vBufferSize), // resource description for a buffer
		D3D12_RESOURCE_STATE_GENERIC_READ, // GPU will read from this buffer and copy its contents to the default heap
		nullptr,
		IID_PPV_ARGS(&iBufferUploadHeap));
	vBufferUploadHeap->SetName(L"Index Buffer Upload Resource Heap");
	
	// store vertex buffer in upload heap
	D3D12_SUBRESOURCE_DATA indexData = {};
	indexData.pData = reinterpret_cast<BYTE*>(iList); // pointer to our index array
	indexData.RowPitch = iBufferSize; // size of all our index buffer
	indexData.SlicePitch = iBufferSize; // also the size of our index buffer
	
	// we are now creating a command with the command list to copy the data from
	// the upload heap to the default heap
	UpdateSubresources(commandList, indexBuffer, iBufferUploadHeap, 0, 0, 1, &indexData);
	
	// transition the vertex buffer data from copy destination state to vertex buffer state
	commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(indexBuffer, D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER));
	
	// create a vertex buffer view for the triangle. We get the GPU memory address to the vertex pointer using the GetGPUVirtualAddress() method
	indexBufferView.BufferLocation = indexBuffer->GetGPUVirtualAddress();
	indexBufferView.Format = DXGI_FORMAT_R32_UINT; // 32-bit unsigned integer (this is what a dword is, double word, a word is 2 bytes)
	indexBufferView.SizeInBytes = iBufferSize;

####Bind the index buffer and draw the quad####
In our UpdatePipeline function, we bind the index buffer to the IA by creating a IASetIndexBuffer command.

After we bind the index buffer, we can draw the quad. To draw indexed primitives, we use the DrawIndexedInstanced() method of our command list instead of the DrawInstanced() command:

	void .[https://msdn.microsoft.com/en-us/library/windows/desktop/dn903874(v=vs.85).aspx][DrawIndexedInstanced](
	  [in] UINT IndexCountPerInstance,
	  [in] UINT InstanceCount,
	  [in] UINT StartIndexLocation,
	  [in] INT  BaseVertexLocation,
	  [in] UINT StartInstanceLocation
	);

 - **IndexCountPerInstance** - *This is the number of indices to draw. If we have triangle list topology set, and we provide a number here that is not a multiple of 3 (an extra 1 or 2 indices), the extra indices are ignored. We have two triangles, each triangle has 3 vertices, so we need 6 indices to represent a quad.*
 - **InstanceCount** - *This is the number of instances we want to draw of this geometry. We only want to draw 1 instance for now, so we set this to 1.*
 - **StartIndexLocation** - *Is is the offset index from the start of our index buffer we want to start drawing. We are starting from the beginning, so we set this to 0.*
 - **BaseVertexLocation** - *This is the offset index in the vertex buffer the indices will start using. We start from the beginning of our vertex buffer so we set this to 0.*
 - **StartInstanceLocation** - *This is a value added to each index before reading per-instance data (used in instancing, which we will talk about in a later tutorial).*

####Cleanup####
We should release the memory we allocated for our index buffer on the GPU, so we release it.

	SAFE_RELEASE(indexBuffer);

Not a very big tutorial, but very useful. Most of the time you will be drawing geometry using an index buffer. Let me know what you think about the tutorial!

####The Code####
##VertexShader.hlsl##
	struct VS_INPUT
	{
		float3 pos : POSITION;
		float4 color: COLOR;
	};
	
	struct VS_OUTPUT
	{
		float4 pos: SV_POSITION;
		float4 color: COLOR;
	};
	
	VS_OUTPUT main(VS_INPUT input)
	{
		VS_OUTPUT output;
		output.pos = float4(input.pos, 1.0f);
		output.color = input.color;
		return output;
	}

##PixelShader.hlsl##
    struct VS_OUTPUT
    {
    	float4 pos: SV_POSITION;
    	float4 color: COLOR;
    };
    	
    float4 main(VS_OUTPUT input) : SV_TARGET
    {
    	// return interpolated color
    	return input.color;
    }

##stdafx.h##
    #pragma once
    
    #ifndef WIN32_LEAN_AND_MEAN
    #define WIN32_LEAN_AND_MEAN    // Exclude rarely-used stuff from Windows headers.
    #endif
    
    #include <windows.h>
    #include <d3d12.h>
    #include <dxgi1_4.h>
    #include <D3Dcompiler.h>
    #include <DirectXMath.h>
    #include "d3dx12.h"
    #include <string>
    
    // this will only call release if an object exists (prevents exceptions calling release on non existant objects)
    #define SAFE_RELEASE(p) { if ( (p) ) { (p)->Release(); (p) = 0; } }
    
    // Handle to the window
    HWND hwnd = NULL;
    
    // name of the window (not the title)
    LPCTSTR WindowName = L"BzTutsApp";
    
    // title of the window
    LPCTSTR WindowTitle = L"Bz Window";
    
    // width and height of the window
    int Width = 800;
    int Height = 600;
    
    // is window full screen?
    bool FullScreen = false;
    
    // we will exit the program when this becomes false
    bool Running = true;
    
    // create a window
    bool InitializeWindow(HINSTANCE hInstance,
    	int ShowWnd,
    	bool fullscreen);
    
    // main application loop
    void mainloop();
    
    // callback function for windows messages
    LRESULT CALLBACK WndProc(HWND hWnd,
    	UINT msg,
    	WPARAM wParam,
    	LPARAM lParam);
    
    // direct3d stuff
    const int frameBufferCount = 3; // number of buffers we want, 2 for double buffering, 3 for tripple buffering
    
    ID3D12Device* device; // direct3d device
    
    IDXGISwapChain3* swapChain; // swapchain used to switch between render targets
    
    ID3D12CommandQueue* commandQueue; // container for command lists
    
    ID3D12DescriptorHeap* rtvDescriptorHeap; // a descriptor heap to hold resources like the render targets
    
    ID3D12Resource* renderTargets[frameBufferCount]; // number of render targets equal to buffer count
    
    ID3D12CommandAllocator* commandAllocator[frameBufferCount]; // we want enough allocators for each buffer * number of threads (we only have one thread)
    
    ID3D12GraphicsCommandList* commandList; // a command list we can record commands into, then execute them to render the frame
    
    ID3D12Fence* fence[frameBufferCount];    // an object that is locked while our command list is being executed by the gpu. We need as many 
    										 //as we have allocators (more if we want to know when the gpu is finished with an asset)
    
    HANDLE fenceEvent; // a handle to an event when our fence is unlocked by the gpu
    
    UINT64 fenceValue[frameBufferCount]; // this value is incremented each frame. each fence will have its own value
    
    int frameIndex; // current rtv we are on
    
    int rtvDescriptorSize; // size of the rtv descriptor on the device (all front and back buffers will be the same size)
    					   // function declarations
    
    bool InitD3D(); // initializes direct3d 12
    
    void Update(); // update the game logic
    
    void UpdatePipeline(); // update the direct3d pipeline (update command lists)
    
    void Render(); // execute the command list
    
    void Cleanup(); // release com ojects and clean up memory
    
    void WaitForPreviousFrame(); // wait until gpu is finished with command list
    
    ID3D12PipelineState* pipelineStateObject; // pso containing a pipeline state
    
    ID3D12RootSignature* rootSignature; // root signature defines data shaders will access
    
    D3D12_VIEWPORT viewport; // area that output from rasterizer will be stretched to.
    
    D3D12_RECT scissorRect; // the area to draw in. pixels outside that area will not be drawn onto
    
    ID3D12Resource* vertexBuffer; // a default buffer in GPU memory that we will load vertex data for our triangle into
    ID3D12Resource* indexBuffer; // a default buffer in GPU memory that we will load index data for our triangle into
    
    D3D12_VERTEX_BUFFER_VIEW vertexBufferView; // a structure containing a pointer to the vertex data in gpu memory
    										   // the total size of the buffer, and the size of each element (vertex)
    
    D3D12_INDEX_BUFFER_VIEW indexBufferView; // a structure holding information about the index buffer

##main.cpp##
    #include "stdafx.h"
    
    using namespace DirectX; // we will be using the directxmath library
    
    struct Vertex {
    	Vertex(float x, float y, float z, float r, float g, float b, float a) : pos(x, y, z), color(r, g, b, z) {}
    	XMFLOAT3 pos;
    	XMFLOAT4 color;
    };
    
    int WINAPI WinMain(HINSTANCE hInstance,    //Main windows function
    	HINSTANCE hPrevInstance,
    	LPSTR lpCmdLine,
    	int nShowCmd)
    
    {
    	// create the window
    	if (!InitializeWindow(hInstance, nShowCmd, FullScreen))
    	{
    		MessageBox(0, L"Window Initialization - Failed",
    			L"Error", MB_OK);
    		return 1;
    	}
    
    	// initialize direct3d
    	if (!InitD3D())
    	{
    		MessageBox(0, L"Failed to initialize direct3d 12",
    			L"Error", MB_OK);
    		Cleanup();
    		return 1;
    	}
    
    	// start the main loop
    	mainloop();
    
    	// we want to wait for the gpu to finish executing the command list before we start releasing everything
    	WaitForPreviousFrame();
    
    	// close the fence event
    	CloseHandle(fenceEvent);
    
    	// clean up everything
    	Cleanup();
    
    	return 0;
    }
    
    // create and show the window
    bool InitializeWindow(HINSTANCE hInstance,
    	int ShowWnd,
    	bool fullscreen)
    
    {
    	if (fullscreen)
    	{
    		HMONITOR hmon = MonitorFromWindow(hwnd,
    			MONITOR_DEFAULTTONEAREST);
    		MONITORINFO mi = { sizeof(mi) };
    		GetMonitorInfo(hmon, &mi);
    
    		Width = mi.rcMonitor.right - mi.rcMonitor.left;
    		Height = mi.rcMonitor.bottom - mi.rcMonitor.top;
    	}
    
    	WNDCLASSEX wc;
    
    	wc.cbSize = sizeof(WNDCLASSEX);
    	wc.style = CS_HREDRAW | CS_VREDRAW;
    	wc.lpfnWndProc = WndProc;
    	wc.cbClsExtra = NULL;
    	wc.cbWndExtra = NULL;
    	wc.hInstance = hInstance;
    	wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    	wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 2);
    	wc.lpszMenuName = NULL;
    	wc.lpszClassName = WindowName;
    	wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    
    	if (!RegisterClassEx(&wc))
    	{
    		MessageBox(NULL, L"Error registering class",
    			L"Error", MB_OK | MB_ICONERROR);
    		return false;
    	}
    
    	hwnd = CreateWindowEx(NULL,
    		WindowName,
    		WindowTitle,
    		WS_OVERLAPPEDWINDOW,
    		CW_USEDEFAULT, CW_USEDEFAULT,
    		Width, Height,
    		NULL,
    		NULL,
    		hInstance,
    		NULL);
    
    	if (!hwnd)
    	{
    		MessageBox(NULL, L"Error creating window",
    			L"Error", MB_OK | MB_ICONERROR);
    		return false;
    	}
    
    	if (fullscreen)
    	{
    		SetWindowLong(hwnd, GWL_STYLE, 0);
    	}
    
    	ShowWindow(hwnd, ShowWnd);
    	UpdateWindow(hwnd);
    
    	return true;
    }
    
    void mainloop() {
    	MSG msg;
    	ZeroMemory(&msg, sizeof(MSG));
    
    	while (Running)
    	{
    		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
    		{
    			if (msg.message == WM_QUIT)
    				break;
    
    			TranslateMessage(&msg);
    			DispatchMessage(&msg);
    		}
    		else {
    			// run game code
    			Update(); // update the game logic
    			Render(); // execute the command queue (rendering the scene is the result of the gpu executing the command lists)
    		}
    	}
    }
    
    LRESULT CALLBACK WndProc(HWND hwnd,
    	UINT msg,
    	WPARAM wParam,
    	LPARAM lParam)
    
    {
    	switch (msg)
    	{
    	case WM_KEYDOWN:
    		if (wParam == VK_ESCAPE) {
    			if (MessageBox(0, L"Are you sure you want to exit?",
    				L"Really?", MB_YESNO | MB_ICONQUESTION) == IDYES)
    			{
    				Running = false;
    				DestroyWindow(hwnd);
    			}
    		}
    		return 0;
    
    	case WM_DESTROY: // x button on top right corner of window was pressed
    		Running = false;
    		PostQuitMessage(0);
    		return 0;
    	}
    	return DefWindowProc(hwnd,
    		msg,
    		wParam,
    		lParam);
    }
    
    bool InitD3D()
    {
    	HRESULT hr;
    
    	// -- Create the Device -- //
    
    	IDXGIFactory4* dxgiFactory;
    	hr = CreateDXGIFactory1(IID_PPV_ARGS(&dxgiFactory));
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	IDXGIAdapter1* adapter; // adapters are the graphics card (this includes the embedded graphics on the motherboard)
    
    	int adapterIndex = 0; // we'll start looking for directx 12  compatible graphics devices starting at index 0
    
    	bool adapterFound = false; // set this to true when a good one was found
    
    							   // find first hardware gpu that supports d3d 12
    	while (dxgiFactory->EnumAdapters1(adapterIndex, &adapter) != DXGI_ERROR_NOT_FOUND)
    	{
    		DXGI_ADAPTER_DESC1 desc;
    		adapter->GetDesc1(&desc);
    
    		if (desc.Flags & DXGI_ADAPTER_FLAG_SOFTWARE)
    		{
    			// we dont want a software device
    			continue;
    		}
    
    		// we want a device that is compatible with direct3d 12 (feature level 11 or higher)
    		hr = D3D12CreateDevice(adapter, D3D_FEATURE_LEVEL_11_0, _uuidof(ID3D12Device), nullptr);
    		if (SUCCEEDED(hr))
    		{
    			adapterFound = true;
    			break;
    		}
    
    		adapterIndex++;
    	}
    
    	if (!adapterFound)
    	{
    		return false;
    	}
    
    	// Create the device
    	hr = D3D12CreateDevice(
    		adapter,
    		D3D_FEATURE_LEVEL_11_0,
    		IID_PPV_ARGS(&device)
    		);
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// -- Create a direct command queue -- //
    
    	D3D12_COMMAND_QUEUE_DESC cqDesc = {};
    	cqDesc.Flags = D3D12_COMMAND_QUEUE_FLAG_NONE;
    	cqDesc.Type = D3D12_COMMAND_LIST_TYPE_DIRECT; // direct means the gpu can directly execute this command queue
    
    	hr = device->CreateCommandQueue(&cqDesc, IID_PPV_ARGS(&commandQueue)); // create the command queue
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// -- Create the Swap Chain (double/tripple buffering) -- //
    
    	DXGI_MODE_DESC backBufferDesc = {}; // this is to describe our display mode
    	backBufferDesc.Width = Width; // buffer width
    	backBufferDesc.Height = Height; // buffer height
    	backBufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; // format of the buffer (rgba 32 bits, 8 bits for each chanel)
    
    														// describe our multi-sampling. We are not multi-sampling, so we set the count to 1 (we need at least one sample of course)
    	DXGI_SAMPLE_DESC sampleDesc = {};
    	sampleDesc.Count = 1; // multisample count (no multisampling, so we just put 1, since we still need 1 sample)
    
    						  // Describe and create the swap chain.
    	DXGI_SWAP_CHAIN_DESC swapChainDesc = {};
    	swapChainDesc.BufferCount = frameBufferCount; // number of buffers we have
    	swapChainDesc.BufferDesc = backBufferDesc; // our back buffer description
    	swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; // this says the pipeline will render to this swap chain
    	swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD; // dxgi will discard the buffer (data) after we call present
    	swapChainDesc.OutputWindow = hwnd; // handle to our window
    	swapChainDesc.SampleDesc = sampleDesc; // our multi-sampling description
    	swapChainDesc.Windowed = !FullScreen; // set to true, then if in fullscreen must call SetFullScreenState with true for full screen to get uncapped fps
    
    	IDXGISwapChain* tempSwapChain;
    
    	dxgiFactory->CreateSwapChain(
    		commandQueue, // the queue will be flushed once the swap chain is created
    		&swapChainDesc, // give it the swap chain description we created above
    		&tempSwapChain // store the created swap chain in a temp IDXGISwapChain interface
    		);
    
    	swapChain = static_cast<IDXGISwapChain3*>(tempSwapChain);
    
    	frameIndex = swapChain->GetCurrentBackBufferIndex();
    
    	// -- Create the Back Buffers (render target views) Descriptor Heap -- //
    
    	// describe an rtv descriptor heap and create
    	D3D12_DESCRIPTOR_HEAP_DESC rtvHeapDesc = {};
    	rtvHeapDesc.NumDescriptors = frameBufferCount; // number of descriptors for this heap.
    	rtvHeapDesc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV; // this heap is a render target view heap
    
    													   // This heap will not be directly referenced by the shaders (not shader visible), as this will store the output from the pipeline
    													   // otherwise we would set the heap's flag to D3D12_DESCRIPTOR_HEAP_FLAG_SHADER_VISIBLE
    	rtvHeapDesc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
    	hr = device->CreateDescriptorHeap(&rtvHeapDesc, IID_PPV_ARGS(&rtvDescriptorHeap));
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// get the size of a descriptor in this heap (this is a rtv heap, so only rtv descriptors should be stored in it.
    	// descriptor sizes may vary from device to device, which is why there is no set size and we must ask the 
    	// device to give us the size. we will use this size to increment a descriptor handle offset
    	rtvDescriptorSize = device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
    
    	// get a handle to the first descriptor in the descriptor heap. a handle is basically a pointer,
    	// but we cannot literally use it like a c++ pointer.
    	CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(rtvDescriptorHeap->GetCPUDescriptorHandleForHeapStart());
    
    	// Create a RTV for each buffer (double buffering is two buffers, tripple buffering is 3).
    	for (int i = 0; i < frameBufferCount; i++)
    	{
    		// first we get the n'th buffer in the swap chain and store it in the n'th
    		// position of our ID3D12Resource array
    		hr = swapChain->GetBuffer(i, IID_PPV_ARGS(&renderTargets[i]));
    		if (FAILED(hr))
    		{
    			return false;
    		}
    
    		// the we "create" a render target view which binds the swap chain buffer (ID3D12Resource[n]) to the rtv handle
    		device->CreateRenderTargetView(renderTargets[i], nullptr, rtvHandle);
    
    		// we increment the rtv handle by the rtv descriptor size we got above
    		rtvHandle.Offset(1, rtvDescriptorSize);
    	}
    
    	// -- Create the Command Allocators -- //
    
    	for (int i = 0; i < frameBufferCount; i++)
    	{
    		hr = device->CreateCommandAllocator(D3D12_COMMAND_LIST_TYPE_DIRECT, IID_PPV_ARGS(&commandAllocator[i]));
    		if (FAILED(hr))
    		{
    			return false;
    		}
    	}
    
    	// -- Create a Command List -- //
    
    	// create the command list with the first allocator
    	hr = device->CreateCommandList(0, D3D12_COMMAND_LIST_TYPE_DIRECT, commandAllocator[frameIndex], NULL, IID_PPV_ARGS(&commandList));
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// -- Create a Fence & Fence Event -- //
    
    	// create the fences
    	for (int i = 0; i < frameBufferCount; i++)
    	{
    		hr = device->CreateFence(0, D3D12_FENCE_FLAG_NONE, IID_PPV_ARGS(&fence[i]));
    		if (FAILED(hr))
    		{
    			return false;
    		}
    		fenceValue[i] = 0; // set the initial fence value to 0
    	}
    
    	// create a handle to a fence event
    	fenceEvent = CreateEvent(nullptr, FALSE, FALSE, nullptr);
    	if (fenceEvent == nullptr)
    	{
    		return false;
    	}
    
    	// create root signature
    
    	CD3DX12_ROOT_SIGNATURE_DESC rootSignatureDesc;
    	rootSignatureDesc.Init(0, nullptr, 0, nullptr, D3D12_ROOT_SIGNATURE_FLAG_ALLOW_INPUT_ASSEMBLER_INPUT_LAYOUT);
    
    	ID3DBlob* signature;
    	hr = D3D12SerializeRootSignature(&rootSignatureDesc, D3D_ROOT_SIGNATURE_VERSION_1, &signature, nullptr);
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	hr = device->CreateRootSignature(0, signature->GetBufferPointer(), signature->GetBufferSize(), IID_PPV_ARGS(&rootSignature));
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// create vertex and pixel shaders
    
    	// when debugging, we can compile the shader files at runtime.
    	// but for release versions, we can compile the hlsl shaders
    	// with fxc.exe to create .cso files, which contain the shader
    	// bytecode. We can load the .cso files at runtime to get the
    	// shader bytecode, which of course is faster than compiling
    	// them at runtime
    
    	// compile vertex shader
    	ID3DBlob* vertexShader; // d3d blob for holding vertex shader bytecode
    	ID3DBlob* errorBuff; // a buffer holding the error data if any
    	hr = D3DCompileFromFile(L"VertexShader.hlsl",
    		nullptr,
    		nullptr,
    		"main",
    		"vs_5_0",
    		D3DCOMPILE_DEBUG | D3DCOMPILE_SKIP_OPTIMIZATION,
    		0,
    		&vertexShader,
    		&errorBuff);
    	if (FAILED(hr))
    	{
    		OutputDebugStringA((char*)errorBuff->GetBufferPointer());
    		return false;
    	}
    
    	// fill out a shader bytecode structure, which is basically just a pointer
    	// to the shader bytecode and the size of the shader bytecode
    	D3D12_SHADER_BYTECODE vertexShaderBytecode = {};
    	vertexShaderBytecode.BytecodeLength = vertexShader->GetBufferSize();
    	vertexShaderBytecode.pShaderBytecode = vertexShader->GetBufferPointer();
    
    	// compile pixel shader
    	ID3DBlob* pixelShader;
    	hr = D3DCompileFromFile(L"PixelShader.hlsl",
    		nullptr,
    		nullptr,
    		"main",
    		"ps_5_0",
    		D3DCOMPILE_DEBUG | D3DCOMPILE_SKIP_OPTIMIZATION,
    		0,
    		&pixelShader,
    		&errorBuff);
    	if (FAILED(hr))
    	{
    		OutputDebugStringA((char*)errorBuff->GetBufferPointer());
    		return false;
    	}
    
    	// fill out shader bytecode structure for pixel shader
    	D3D12_SHADER_BYTECODE pixelShaderBytecode = {};
    	pixelShaderBytecode.BytecodeLength = pixelShader->GetBufferSize();
    	pixelShaderBytecode.pShaderBytecode = pixelShader->GetBufferPointer();
    
    	// create input layout
    
    	// The input layout is used by the Input Assembler so that it knows
    	// how to read the vertex data bound to it.
    
    	D3D12_INPUT_ELEMENT_DESC inputLayout[] =
    	{
    		{ "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 },
    		{ "COLOR", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 0, 12, D3D12_INPUT_CLASSIFICATION_PER_VERTEX_DATA, 0 }
    	};
    
    	// fill out an input layout description structure
    	D3D12_INPUT_LAYOUT_DESC inputLayoutDesc = {};
    
    	// we can get the number of elements in an array by "sizeof(array) / sizeof(arrayElementType)"
    	inputLayoutDesc.NumElements = sizeof(inputLayout) / sizeof(D3D12_INPUT_ELEMENT_DESC);
    	inputLayoutDesc.pInputElementDescs = inputLayout;
    
    	// create a pipeline state object (PSO)
    
    	// In a real application, you will have many pso's. for each different shader
    	// or different combinations of shaders, different blend states or different rasterizer states,
    	// different topology types (point, line, triangle, patch), or a different number
    	// of render targets you will need a pso
    
    	// VS is the only required shader for a pso. You might be wondering when a case would be where
    	// you only set the VS. It's possible that you have a pso that only outputs data with the stream
    	// output, and not on a render target, which means you would not need anything after the stream
    	// output.
    
    	D3D12_GRAPHICS_PIPELINE_STATE_DESC psoDesc = {}; // a structure to define a pso
    	psoDesc.InputLayout = inputLayoutDesc; // the structure describing our input layout
    	psoDesc.pRootSignature = rootSignature; // the root signature that describes the input data this pso needs
    	psoDesc.VS = vertexShaderBytecode; // structure describing where to find the vertex shader bytecode and how large it is
    	psoDesc.PS = pixelShaderBytecode; // same as VS but for pixel shader
    	psoDesc.PrimitiveTopologyType = D3D12_PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; // type of topology we are drawing
    	psoDesc.RTVFormats[0] = DXGI_FORMAT_R8G8B8A8_UNORM; // format of the render target
    	psoDesc.SampleDesc = sampleDesc; // must be the same sample description as the swapchain and depth/stencil buffer
    	psoDesc.SampleMask = 0xffffffff; // sample mask has to do with multi-sampling. 0xffffffff means point sampling is done
    	psoDesc.RasterizerState = CD3DX12_RASTERIZER_DESC(D3D12_DEFAULT); // a default rasterizer state.
    	psoDesc.BlendState = CD3DX12_BLEND_DESC(D3D12_DEFAULT); // a default blent state.
    	psoDesc.NumRenderTargets = 1; // we are only binding one render target
    
    	// create the pso
    	hr = device->CreateGraphicsPipelineState(&psoDesc, IID_PPV_ARGS(&pipelineStateObject));
    	if (FAILED(hr))
    	{
    		return false;
    	}
    
    	// Create vertex buffer
    
    	// a triangle
    	Vertex vList[] = {
    		{ -0.5f,  0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f },
    		{  0.5f, -0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f },
    		{ -0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f },
    		{  0.5f,  0.5f, 0.5f, 1.0f, 0.0f, 1.0f, 1.0f }
    	};
    
    	int vBufferSize = sizeof(vList);
    
    	// create default heap
    	// default heap is memory on the GPU. Only the GPU has access to this memory
    	// To get data into this heap, we will have to upload the data using
    	// an upload heap
    	device->CreateCommittedResource(
    		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT), // a default heap
    		D3D12_HEAP_FLAG_NONE, // no flags
    		&CD3DX12_RESOURCE_DESC::Buffer(vBufferSize), // resource description for a buffer
    		D3D12_RESOURCE_STATE_COPY_DEST, // we will start this heap in the copy destination state since we will copy data
    										// from the upload heap to this heap
    		nullptr, // optimized clear value must be null for this type of resource. used for render targets and depth/stencil buffers
    		IID_PPV_ARGS(&vertexBuffer));
    
    	// we can give resource heaps a name so when we debug with the graphics debugger we know what resource we are looking at
    	vertexBuffer->SetName(L"Vertex Buffer Resource Heap");
    
    	// create upload heap
    	// upload heaps are used to upload data to the GPU. CPU can write to it, GPU can read from it
    	// We will upload the vertex buffer using this heap to the default heap
    	ID3D12Resource* vBufferUploadHeap;
    	device->CreateCommittedResource(
    		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_UPLOAD), // upload heap
    		D3D12_HEAP_FLAG_NONE, // no flags
    		&CD3DX12_RESOURCE_DESC::Buffer(vBufferSize), // resource description for a buffer
    		D3D12_RESOURCE_STATE_GENERIC_READ, // GPU will read from this buffer and copy its contents to the default heap
    		nullptr,
    		IID_PPV_ARGS(&vBufferUploadHeap));
    	vBufferUploadHeap->SetName(L"Vertex Buffer Upload Resource Heap");
    
    	// store vertex buffer in upload heap
    	D3D12_SUBRESOURCE_DATA vertexData = {};
    	vertexData.pData = reinterpret_cast<BYTE*>(vList); // pointer to our vertex array
    	vertexData.RowPitch = vBufferSize; // size of all our triangle vertex data
    	vertexData.SlicePitch = vBufferSize; // also the size of our triangle vertex data
    
    	// we are now creating a command with the command list to copy the data from
    	// the upload heap to the default heap
    	UpdateSubresources(commandList, vertexBuffer, vBufferUploadHeap, 0, 0, 1, &vertexData);
    
    	// transition the vertex buffer data from copy destination state to vertex buffer state
    	commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(vertexBuffer, D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER));
    
    	// Create index buffer
    
    	// a quad (2 triangles)
    	DWORD iList[] = {
    		0, 1, 2, // first triangle
    		0, 3, 1 // second triangle
    	};
    
    	int iBufferSize = sizeof(iList);
    
    	// create default heap to hold index buffer
    	device->CreateCommittedResource(
    		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT), // a default heap
    		D3D12_HEAP_FLAG_NONE, // no flags
    		&CD3DX12_RESOURCE_DESC::Buffer(iBufferSize), // resource description for a buffer
    		D3D12_RESOURCE_STATE_COPY_DEST, // start in the copy destination state
    		nullptr, // optimized clear value must be null for this type of resource
    		IID_PPV_ARGS(&indexBuffer));
    
    	// we can give resource heaps a name so when we debug with the graphics debugger we know what resource we are looking at
    	vertexBuffer->SetName(L"Index Buffer Resource Heap");
    
    	// create upload heap to upload index buffer
    	ID3D12Resource* iBufferUploadHeap;
    	device->CreateCommittedResource(
    		&CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_UPLOAD), // upload heap
    		D3D12_HEAP_FLAG_NONE, // no flags
    		&CD3DX12_RESOURCE_DESC::Buffer(vBufferSize), // resource description for a buffer
    		D3D12_RESOURCE_STATE_GENERIC_READ, // GPU will read from this buffer and copy its contents to the default heap
    		nullptr,
    		IID_PPV_ARGS(&iBufferUploadHeap));
    	vBufferUploadHeap->SetName(L"Index Buffer Upload Resource Heap");
    
    	// store vertex buffer in upload heap
    	D3D12_SUBRESOURCE_DATA indexData = {};
    	indexData.pData = reinterpret_cast<BYTE*>(iList); // pointer to our index array
    	indexData.RowPitch = iBufferSize; // size of all our index buffer
    	indexData.SlicePitch = iBufferSize; // also the size of our index buffer
    
    	// we are now creating a command with the command list to copy the data from
    	// the upload heap to the default heap
    	UpdateSubresources(commandList, indexBuffer, iBufferUploadHeap, 0, 0, 1, &indexData);
    
    	// transition the vertex buffer data from copy destination state to vertex buffer state
    	commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(indexBuffer, D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER));
    
    	// Now we execute the command list to upload the initial assets (triangle data)
    	commandList->Close();
    	ID3D12CommandList* ppCommandLists[] = { commandList };
    	commandQueue->ExecuteCommandLists(_countof(ppCommandLists), ppCommandLists);
    
    	// increment the fence value now, otherwise the buffer might not be uploaded by the time we start drawing
    	fenceValue[frameIndex]++;
    	hr = commandQueue->Signal(fence[frameIndex], fenceValue[frameIndex]);
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    
    	// create a vertex buffer view for the triangle. We get the GPU memory address to the vertex pointer using the GetGPUVirtualAddress() method
    	vertexBufferView.BufferLocation = vertexBuffer->GetGPUVirtualAddress();
    	vertexBufferView.StrideInBytes = sizeof(Vertex);
    	vertexBufferView.SizeInBytes = vBufferSize;
    
    	// create a vertex buffer view for the triangle. We get the GPU memory address to the vertex pointer using the GetGPUVirtualAddress() method
    	indexBufferView.BufferLocation = indexBuffer->GetGPUVirtualAddress();
    	indexBufferView.Format = DXGI_FORMAT_R32_UINT; // 32-bit unsigned integer (this is what a dword is, double word, a word is 2 bytes)
    	indexBufferView.SizeInBytes = iBufferSize;
    
    	// Fill out the Viewport
    	viewport.TopLeftX = 0;
    	viewport.TopLeftY = 0;
    	viewport.Width = Width;
    	viewport.Height = Height;
    	viewport.MinDepth = 0.0f;
    	viewport.MaxDepth = 1.0f;
    
    	// Fill out a scissor rect
    	scissorRect.left = 0;
    	scissorRect.top = 0;
    	scissorRect.right = Width;
    	scissorRect.bottom = Height;
    
    	return true;
    }
    
    void Update()
    {
    	// update app logic, such as moving the camera or figuring out what objects are in view
    }
    
    void UpdatePipeline()
    {
    	HRESULT hr;
    
    	// We have to wait for the gpu to finish with the command allocator before we reset it
    	WaitForPreviousFrame();
    
    	// we can only reset an allocator once the gpu is done with it
    	// resetting an allocator frees the memory that the command list was stored in
    	hr = commandAllocator[frameIndex]->Reset();
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    
    	// reset the command list. by resetting the command list we are putting it into
    	// a recording state so we can start recording commands into the command allocator.
    	// the command allocator that we reference here may have multiple command lists
    	// associated with it, but only one can be recording at any time. Make sure
    	// that any other command lists associated to this command allocator are in
    	// the closed state (not recording).
    	// Here you will pass an initial pipeline state object as the second parameter,
    	// but in this tutorial we are only clearing the rtv, and do not actually need
    	// anything but an initial default pipeline, which is what we get by setting
    	// the second parameter to NULL
    	hr = commandList->Reset(commandAllocator[frameIndex], pipelineStateObject);
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    
    	// here we start recording commands into the commandList (which all the commands will be stored in the commandAllocator)
    
    	// transition the "frameIndex" render target from the present state to the render target state so the command list draws to it starting from here
    	commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(renderTargets[frameIndex], D3D12_RESOURCE_STATE_PRESENT, D3D12_RESOURCE_STATE_RENDER_TARGET));
    
    	// here we again get the handle to our current render target view so we can set it as the render target in the output merger stage of the pipeline
    	CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(rtvDescriptorHeap->GetCPUDescriptorHandleForHeapStart(), frameIndex, rtvDescriptorSize);
    
    	// set the render target for the output merger stage (the output of the pipeline)
    	commandList->OMSetRenderTargets(1, &rtvHandle, FALSE, nullptr);
    
    	// Clear the render target by using the ClearRenderTargetView command
    	const float clearColor[] = { 0.0f, 0.2f, 0.4f, 1.0f };
    	commandList->ClearRenderTargetView(rtvHandle, clearColor, 0, nullptr);
    
    	// draw triangle
    	commandList->SetGraphicsRootSignature(rootSignature); // set the root signature
    	commandList->RSSetViewports(1, &viewport); // set the viewports
    	commandList->RSSetScissorRects(1, &scissorRect); // set the scissor rects
    	commandList->IASetPrimitiveTopology(D3D_PRIMITIVE_TOPOLOGY_TRIANGLELIST); // set the primitive topology
    	commandList->IASetVertexBuffers(0, 1, &vertexBufferView); // set the vertex buffer (using the vertex buffer view)
    	commandList->IASetIndexBuffer(&indexBufferView);
    	commandList->DrawIndexedInstanced(6, 1, 0, 0, 0); // draw 2 triangles (draw 1 instance of 2 triangles)
    
    	// transition the "frameIndex" render target from the render target state to the present state. If the debug layer is enabled, you will receive a
    	// warning if present is called on the render target when it's not in the present state
    	commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(renderTargets[frameIndex], D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_PRESENT));
    
    	hr = commandList->Close();
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    }
    
    void Render()
    {
    	HRESULT hr;
    
    	UpdatePipeline(); // update the pipeline by sending commands to the commandqueue
    
    	// create an array of command lists (only one command list here)
    	ID3D12CommandList* ppCommandLists[] = { commandList };
    
    	// execute the array of command lists
    	commandQueue->ExecuteCommandLists(_countof(ppCommandLists), ppCommandLists);
    
    	// this command goes in at the end of our command queue. we will know when our command queue 
    	// has finished because the fence value will be set to "fenceValue" from the GPU since the command
    	// queue is being executed on the GPU
    	hr = commandQueue->Signal(fence[frameIndex], fenceValue[frameIndex]);
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    
    	// present the current backbuffer
    	hr = swapChain->Present(0, 0);
    	if (FAILED(hr))
    	{
    		Running = false;
    	}
    }
    
    void Cleanup()
    {
    	// wait for the gpu to finish all frames
    	for (int i = 0; i < frameBufferCount; ++i)
    	{
    		frameIndex = i;
    		WaitForPreviousFrame();
    	}
    
    	// get swapchain out of full screen before exiting
    	BOOL fs = false;
    	if (swapChain->GetFullscreenState(&fs, NULL))
    		swapChain->SetFullscreenState(false, NULL);
    
    	SAFE_RELEASE(device);
    	SAFE_RELEASE(swapChain);
    	SAFE_RELEASE(commandQueue);
    	SAFE_RELEASE(rtvDescriptorHeap);
    	SAFE_RELEASE(commandList);
    
    	for (int i = 0; i < frameBufferCount; ++i)
    	{
    		SAFE_RELEASE(renderTargets[i]);
    		SAFE_RELEASE(commandAllocator[i]);
    		SAFE_RELEASE(fence[i]);
    	};
    
    	SAFE_RELEASE(pipelineStateObject);
    	SAFE_RELEASE(rootSignature);
    	SAFE_RELEASE(vertexBuffer);
    	SAFE_RELEASE(indexBuffer);
    }
    
    void WaitForPreviousFrame()
    {
    	HRESULT hr;
    
    	// swap the current rtv buffer index so we draw on the correct buffer
    	frameIndex = swapChain->GetCurrentBackBufferIndex();
    
    	// if the current fence value is still less than "fenceValue", then we know the GPU has not finished executing
    	// the command queue since it has not reached the "commandQueue->Signal(fence, fenceValue)" command
    	if (fence[frameIndex]->GetCompletedValue() < fenceValue[frameIndex])
    	{
    		// we have the fence create an event which is signaled once the fence's current value is "fenceValue"
    		hr = fence[frameIndex]->SetEventOnCompletion(fenceValue[frameIndex], fenceEvent);
    		if (FAILED(hr))
    		{
    			Running = false;
    		}
    
    		// We will wait until the fence has triggered the event that it's current value has reached "fenceValue". once it's value
    		// has reached "fenceValue", we know the command queue has finished executing
    		WaitForSingleObject(fenceEvent, INFINITE);
    	}
    
    	// increment fenceValue for next frame
    	fenceValue[frameIndex]++;
    }