提要
前几天非常easy地跑了一个DirectX 9 程序，以为DirectX就那么绘制，事实证明有点Naive了。
之前的那个程序最多也就是个固定流水线的东西。
可是今天要用DirectX11来写一个小的框架。
龙书就不要看了，看Introduction to 3D GAME PROGRAMMING WITH DIRECTX®11
几个重要的类
ID3D11Device : 一个虚拟适配器。它被用于执行渲染和创建资源。
ID3D11DeviceContext: represents a device context which generates rendering commands.
ID3D11RenderTargetView: identifies the render-target subresources that can be accessed during rendering.
ID3D11InputLayout: An input-layout interface holds a definition of how to feed vertex data that is laid out in memory into the input-assembler stage of the graphics pipeline.
渲染流水线（翻译自微软文档）
DirectX编程流水线是为了实时游戏应用设计的，上图显示了由输入到输出的各个阶段的数据流向。相对于DirectX10 的图形流水线。DirectX11加入了一些额外的Stage来支持一些新的特性。
你能够使用DirectX 11API来配置全部的Stage，通过HLSL语言来设置就能够了。这样整个流水线就拥有非常大的可扩展性和适应性了。
以下列出每一个阶段所做的事情.
Input-Assembler Stage : 提供渲染时的数据（三角形，线。点）。
Vertex-Shader Stage：处理顶点，通常的操作有：Transformmation，蒙皮，光照计算。通常一个VertexShader输入是一组顶点，输出也是一组顶点。
Geometry-Shader Statge：这个阶段会处理全部的图元，输入是完整的图元（三角形就是三个顶点，线段就是两个顶点，还有就是单个的点）。
另外。每一个图元能够包括邻接图元的信息。另外这个阶段还能够对图元进行一定的简化和精细化。
给定一个图元，geometry shader能够丢弃这个图元，或者能够生成新的一个或者多个的图元。
Stream-Output Stage: 从上一个阶段流下来的数据，能够将图元信息从流水线放入到存储中。或者放到Rasterizer阶段。被放到内存中的数据能够再次放到流水线中。或者被CPU读取。
Rasterizer Stage：裁剪图元，为pixel shader准备图元，并准备如何调用pixel shader.
Pixel-Shader Stage: 收到经过插值的结果，生成终于的图像。
Output-Merger Stage ：合并各种类型的输出信息(pixel shader 值。深度信息，Stencil值)。并和当前render target的深度/Stencil 缓存。得到最后的流水线结果。
Tessellation stage：这个阶段由Hull-shader, tessellator还有domain-shader组成，它主要是将高阶表面转换成一系列的三角行。然后放到流水线中。
Direct3D 11 可编程流水线也能够用快速的计算任务。一个compute shader能够将Direct3D11扩展用于通用GPU计算。
用Shader绘制一个三角形
Direct3D。我们须要完毕以下几个步骤：
1.定义我们须要检查的设备类型（device types）和特征级别（feature levels）
2.创建Direct3D设备。渲染设备（context）和交换链（swap chain）。
3.创建渲染目标（render target）。
4.设置视口（viewport）
5.開始渲染
6.渲染模型
7.清屏幕
代码清单
// include the basic windows header files and the Direct3D header files
#include <windows.h>
#include <windowsx.h>
#include <d3d11.h>
#include <d3dx11.h>
#include <d3dx10.h>
#include "assimpmodel.h"
// include the Direct3D Library file
#pragma comment (lib, "d3d11.lib")
#pragma comment (lib, "d3dx11.lib")
#pragma comment (lib, "d3dx10.lib")
// define the screen resolution
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600
// global declarations
IDXGISwapChain *swapchain; // the pointer to the swap chain interface
ID3D11Device *dev; // the pointer to our Direct3D device interface
ID3D11DeviceContext *devcon; // the pointer to our Direct3D device context
ID3D11RenderTargetView *backbuffer; // the pointer to our back buffer
ID3D11InputLayout *pLayout; // the pointer to the input layout
ID3D11VertexShader *pVS; // the pointer to the vertex shader
ID3D11PixelShader *pPS; // the pointer to the pixel shader
ID3D11Buffer *pVBuffer; // the pointer to the vertex buffer
// a struct to define a single vertex
struct VERTEX{ D3DXVECTOR3 position; D3DXCOLOR Color; };
// function prototypes
void InitD3D(HWND hWnd); // sets up and initializes Direct3D
void RenderFrame(void); // renders a single frame
void CleanD3D(void); // closes Direct3D and releases memory
void InitGraphics(void); // creates the shape to render
void InitPipeline(void); // loads and prepares the shaders
// the WindowProc function prototype
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
// the entry point for any Windows program
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
HWND hWnd;
WNDCLASSEX wc;
ZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = WindowProc;
wc.hInstance = hInstance;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.lpszClassName = "WindowClass";
RegisterClassEx(&wc);
RECT wr = { 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT };
AdjustWindowRect(&wr, WS_OVERLAPPEDWINDOW, FALSE);
hWnd = CreateWindowEx(NULL,
"WindowClass",
"Triangle",
WS_OVERLAPPEDWINDOW,
300,
300,
wr.right - wr.left,
wr.bottom - wr.top,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hWnd, nCmdShow);
// set up and initialize Direct3D
InitD3D(hWnd);
// enter the main loop:
MSG msg;
while (TRUE)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
if (msg.message == WM_QUIT)
break;
}
RenderFrame();
}
// clean up DirectX and COM
CleanD3D();
return msg.wParam;
}
// this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_DESTROY:
{
PostQuitMessage(0);
return 0;
} break;
}
return DefWindowProc(hWnd, message, wParam, lParam);
}
// this function initializes and prepares Direct3D for use
void InitD3D(HWND hWnd)
{
// create a struct to hold information about the swap chain
DXGI_SWAP_CHAIN_DESC scd;
// clear out the struct for use
ZeroMemory(&scd, sizeof(DXGI_SWAP_CHAIN_DESC));
// fill the swap chain description struct
scd.BufferCount = 1; // one back buffer
scd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; // use 32-bit color
scd.BufferDesc.Width = SCREEN_WIDTH; // set the back buffer width
scd.BufferDesc.Height = SCREEN_HEIGHT; // set the back buffer height
scd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; // how swap chain is to be used
scd.OutputWindow = hWnd; // the window to be used
scd.SampleDesc.Count = 4; // how many multisamples
scd.Windowed = TRUE; // windowed/full-screen mode
scd.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH; // allow full-screen switching
// create a device, device context and swap chain using the information in the scd struct
D3D11CreateDeviceAndSwapChain(NULL,
D3D_DRIVER_TYPE_HARDWARE,
NULL,
NULL,
NULL,
NULL,
D3D11_SDK_VERSION,
&scd,
&swapchain,
&dev,
NULL,
&devcon);
// get the address of the back buffer
ID3D11Texture2D *pBackBuffer;
swapchain->GetBuffer(0, __uuidof(ID3D11Texture2D), (LPVOID*)&pBackBuffer);
// use the back buffer address to create the render target
dev->CreateRenderTargetView(pBackBuffer, NULL, &backbuffer);
pBackBuffer->Release();
// set the render target as the back buffer
devcon->OMSetRenderTargets(1, &backbuffer, NULL);
// Set the viewport
D3D11_VIEWPORT viewport;
ZeroMemory(&viewport, sizeof(D3D11_VIEWPORT));
viewport.TopLeftX = 0;
viewport.TopLeftY = 0;
viewport.Width = SCREEN_WIDTH;
viewport.Height = SCREEN_HEIGHT;
devcon->RSSetViewports(1, &viewport);
InitPipeline();
InitGraphics();
}
// this is the function used to render a single frame
void RenderFrame(void)
{
// clear the back buffer to a deep blue
devcon->ClearRenderTargetView(backbuffer, D3DXCOLOR(0.0f, 0.2f, 0.4f, 1.0f));
// select which vertex buffer to display
UINT stride = sizeof(VERTEX);
UINT offset = 0;
devcon->IASetVertexBuffers(0, 1, &pVBuffer, &stride, &offset);
// select which primtive type we are using
devcon->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
// draw the vertex buffer to the back buffer
devcon->Draw(3, 0);
// switch the back buffer and the front buffer
swapchain->Present(0, 0);
}
// this is the function that cleans up Direct3D and COM
void CleanD3D(void)
{
swapchain->SetFullscreenState(FALSE, NULL); // switch to windowed mode
// close and release all existing COM objects
pLayout->Release();
pVS->Release();
pPS->Release();
pVBuffer->Release();
swapchain->Release();
backbuffer->Release();
dev->Release();
devcon->Release();
}
// this is the function that creates the shape to render
void InitGraphics()
{
//Assimpmodel *model = new Assimpmodel();
//model->Initialize(dev);
// create a triangle using the VERTEX struct
VERTEX OurVertices[] =
{
{ D3DXVECTOR3(0.0f, 0.5f, 0.0f), D3DXCOLOR(1.0f, 0.0f, 0.0f, 1.0f) },
{ D3DXVECTOR3(0.45f, -0.5, 0.0f), D3DXCOLOR(0.0f, 1.0f, 0.0f, 1.0f) },
{ D3DXVECTOR3(-0.45f, -0.5f, 0.0f), D3DXCOLOR(0.0f, 0.0f, 1.0f, 1.0f) }
};
// create the vertex buffer
D3D11_BUFFER_DESC bd;
ZeroMemory(&bd, sizeof(bd));
bd.Usage = D3D11_USAGE_DYNAMIC; // write access access by CPU and GPU
bd.ByteWidth = sizeof(VERTEX)* 3; // size is the VERTEX struct * 3
bd.BindFlags = D3D11_BIND_VERTEX_BUFFER; // use as a vertex buffer
bd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE; // allow CPU to write in buffer
dev->CreateBuffer(&bd, NULL, &pVBuffer); // create the buffer
// copy the vertices into the buffer
D3D11_MAPPED_SUBRESOURCE ms;
devcon->Map(pVBuffer, NULL, D3D11_MAP_WRITE_DISCARD, NULL, &ms); // map the buffer
memcpy(ms.pData, OurVertices, sizeof(OurVertices)); // copy the data
devcon->Unmap(pVBuffer, NULL); // unmap the buffer
}
// this function loads and prepares the shaders
void InitPipeline()
{
// load and compile the two shaders
ID3D10Blob *VS, *PS;
D3DX11CompileFromFile("shaders.shader", 0, 0, "VShader", "vs_5_0", 0, 0, 0, &VS, 0, 0);
D3DX11CompileFromFile("shaders.shader", 0, 0, "PShader", "ps_5_0", 0, 0, 0, &PS, 0, 0);
// encapsulate both shaders into shader objects
dev->CreateVertexShader(VS->GetBufferPointer(), VS->GetBufferSize(), NULL, &pVS);
dev->CreatePixelShader(PS->GetBufferPointer(), PS->GetBufferSize(), NULL, &pPS);
// set the shader objects
devcon->VSSetShader(pVS, 0, 0);
devcon->PSSetShader(pPS, 0, 0);
// create the input layout object
D3D11_INPUT_ELEMENT_DESC ied[] =
{
{ "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 },
{ "COLOR", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 0, 12, D3D11_INPUT_PER_VERTEX_DATA, 0 },
};
dev->CreateInputLayout(ied, 2, VS->GetBufferPointer(), VS->GetBufferSize(), &pLayout);
devcon->IASetInputLayout(pLayout);
}shader.shader
struct VOut
{
float4 position : SV_POSITION;
float4 color : COLOR;
};
VOut VShader(float4 position : POSITION, float4 color : COLOR)
{
VOut output;
output.position = position;
output.color = color;
return output;
}
float4 PShader(float4 position : SV_POSITION, float4 color : COLOR) : SV_TARGET
{
return color;
}代码就不具体说了，具体能够看參考的链接。
结果例如以下
封装出一个简单的框架
将全部的代码都写在main.cpp里肯定不是太好，最好按功能抽象出各种类型。以下是參照教程写的一个框架。
简单的一个框架。还是渲染一个小小的三角形。可是是抽了非常多个类出来。比方相机，输入之类的，方面后面扩展。
当然还是一个比較槽的框架哈。
代码直接看github吧。
參考
Graphics Pipeline - https://msdn.microsoft.com/en-us/library/windows/desktop/ff476882(v=vs.85).aspx
《Introduction to 3D GAME PROGRAMMING WITH DIRECTX®11》
DirectX 11 Tutorials - http://www.rastertek.com/tutdx11.html
http://www.directxtutorial.com/default.aspx