1. 得到画布

D3D中，所有画图的操作都是在IDirect3DDevice9 中的，所以我们就可以

这样声明： IDirect3DDevice9* Device = 0;

出生化之(略)

2. 准备好相关的点

D3D中，花点用了两个Buffer， vertex buffer 用来保存相关的点的值，

index buffer 用来保存点之间连接的索引。

首先我们可以这样声明一个结构体：

struct	Vertex
{
	Vertex(){}
	Vertex(float x, float y, float z)
	{
		m_x = x; 
		m_y = y;
		m_z = z;
	}

	float m_x, m_y, m_z;
	static const DWORD FVF;
};

const DWORD Vertex::FVF = D3DFVF_XYZ;

然后利用 CreateVertexBuffer 和 CreateIndexBuffer 创建 vertex buffer 和 index buffer

	Device->CreateVertexBuffer(
		8 * sizeof(Vertex), 
		D3DUSAGE_WRITEONLY,
		Vertex::FVF,
		D3DPOOL_MANAGED,
		&VB,
		0);

	Device->CreateIndexBuffer(
		36 * sizeof(WORD),
		D3DUSAGE_WRITEONLY,
		D3DFMT_INDEX16,
		D3DPOOL_MANAGED,
		&IB,
		0);

最后填充vertex buffer 和 index buffer。

我们得到了相关的vertex buffer 和index buffer之后，我们就去为这些点赋值。

我们用Lock函数得到相应的内存位置，复制完成以后用Unlock 释放.

	Vertex* vertices;
	VB->Lock(0, 0, (void**)&vertices, 0);

	// vertices of a unit cube
	vertices[0] = Vertex(-1.0f, -1.0f, -1.0f);
	vertices[1] = Vertex(-1.0f,  1.0f, -1.0f);
	vertices[2] = Vertex( 1.0f,  1.0f, -1.0f);
	vertices[3] = Vertex( 1.0f, -1.0f, -1.0f);
	vertices[4] = Vertex(-1.0f, -1.0f,  1.0f);
	vertices[5] = Vertex(-1.0f,  1.0f,  1.0f);
	vertices[6] = Vertex( 1.0f,  1.0f,  1.0f);
	vertices[7] = Vertex( 1.0f, -1.0f,  1.0f);

	VB->Unlock();

	// define the triangles of the cube:
	WORD* indices = 0;
	IB->Lock(0, 0, (void**)&indices, 0);

	// front side
	indices[0]  = 0; indices[1]  = 1; indices[2]  = 2;
	indices[3]  = 0; indices[4]  = 2; indices[5]  = 3;

	// back side
	indices[6]  = 4; indices[7]  = 6; indices[8]  = 5;
	indices[9]  = 4; indices[10] = 7; indices[11] = 6;

	// left side
	indices[12] = 4; indices[13] = 5; indices[14] = 1;
	indices[15] = 4; indices[16] = 1; indices[17] = 0;

	// right side
	indices[18] = 3; indices[19] = 2; indices[20] = 6;
	indices[21] = 3; indices[22] = 6; indices[23] = 7;

	// top
	indices[24] = 1; indices[25] = 5; indices[26] = 6;
	indices[27] = 1; indices[28] = 6; indices[29] = 2;

	// bottom
	indices[30] = 4; indices[31] = 0; indices[32] = 3;
	indices[33] = 4; indices[34] = 3; indices[35] = 7;

	IB->Unlock();

3. 准备好摄像机

	D3DXVECTOR3 position(0.0f, 0.0f, -5.0f);
	D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);
	D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);
	D3DXMATRIX V;
	D3DXMatrixLookAtLH(&V, &position, &target, &up);

	Device->SetTransform(D3DTS_VIEW, &V);

4. 用2维图像来表现3维效果

设置 projection:

	D3DXMATRIX proj;
	D3DXMatrixPerspectiveFovLH(
		&proj,
		D3DX_PI * 0.5f, // 90 - degree
		(float)Width / (float)Height,
		1.0f,
		1000.0f);
	Device->SetTransform(D3DTS_PROJECTION, &proj);

设置渲染模式:

Device->SetRenderState(D3DRS_FILLMODE, D3DFILL_WIREFRAME);

5. 开始画了

当一切准备就绪之后就可以用vertex buffer 和index buf 中的内容画三角形了。

但是要画东西出来却需要遵循一下三步：

(1).把 vertex buffer 中的内容放到一个 stream 中，这是stream会最终把几何图型渲染成为图像。

相应的函数是SetStreamSource

(2).设置点的格式，利用SetFVF函数

(3).设置 index buffer，调用的是函数 SetIndices

在开始之前，我们把屏幕背景填充成白色：

Device->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0xffffffff, 1.0f, 0);

然后就开始画立方体：

		Device->BeginScene();

		Device->SetStreamSource(0, VB, 0, sizeof(Vertex));
		Device->SetIndices(IB);
		Device->SetFVF(Vertex::FVF);

		// Draw cube.
		Device->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0, 8, 0, 12);

		Device->EndScene();
		Device->Present(0, 0, 0, 0);

好了这样一个简单的立方体就出来了。