DirectX 光源、光照模型

顶点格式中只有D3DFVF_DIFFUSE时，顶点的颜色值所呈现的是制定的颜色值。

当使用D3DFVF_DIFFUSE | D3DFVF_NORMAL，顶点的颜色值，完全由材质、光照计算。

//-----------------------------------------------------------------------------
// Desc: 顶点结构
//-----------------------------------------------------------------------------
struct CUSTOMVERTEX
{
    D3DXVECTOR3 position;   //顶点位置
    D3DXVECTOR3 normal;     //顶点法线
};
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_NORMAL)


//-----------------------------------------------------------------------------
// Desc: 设置变换矩阵
//-----------------------------------------------------------------------------
VOID SetMatrices()
{
	//建立并设置世界矩阵
    D3DXMATRIX matWorld;
	D3DXMatrixIdentity( &matWorld );
    g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

	//建立并设置观察矩阵
    D3DXVECTOR3 vEyePt( 0.0f, 3.0f,-5.0f );
    D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );
    D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f );
    D3DXMATRIX matView;
    D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
    g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );

    //建立并设置投影矩阵
    D3DXMATRIX matProj;
    D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 1.0f, 1.0f, 100.0f );
    g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );
}


//-----------------------------------------------------------------------------
// Desc: 初始化Direct3D
//-----------------------------------------------------------------------------
HRESULT InitD3D( HWND hWnd )
{
	//创建Direct3D对象, 该对象用于创建Direct3D设备对象
    if( NULL == ( g_pD3D = Direct3DCreate9( D3D_SDK_VERSION ) ) )
        return E_FAIL;

    //设置D3DPRESENT_PARAMETERS结构, 准备创建Direct3D设备对象
    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory( &d3dpp, sizeof(d3dpp) );
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
    d3dpp.EnableAutoDepthStencil = TRUE;
    d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
	

    //创建Direct3D设备对象
    if( FAILED( g_pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
                                      D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                                      &d3dpp, &g_pd3dDevice ) ) )
    {
        return E_FAIL;
    }

    //设置剔出模式为不剔出任何面(正面和方面)
    g_pd3dDevice->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE );

    //启用深度测试
    g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, TRUE );

	//启用镜面反射光照模型
	g_pd3dDevice->SetRenderState(D3DRS_SPECULARENABLE, TRUE);
	
	//设置变换矩阵
	SetMatrices();

    return S_OK;
}


//-----------------------------------------------------------------------------
// Desc: 创建场景图形
//-----------------------------------------------------------------------------
HRESULT InitGeometry()
{
    //创顶点缓冲区
    if( FAILED( g_pd3dDevice->CreateVertexBuffer( 50*2*sizeof(CUSTOMVERTEX),
                                                  0, D3DFVF_CUSTOMVERTEX,
                                                  D3DPOOL_DEFAULT, &g_pVB, NULL ) ) )
    {
        return E_FAIL;
    }

    //填充顶点缓冲区
    CUSTOMVERTEX* pVertices;
    if( FAILED( g_pVB->Lock( 0, 0, (void**)&pVertices, 0 ) ) )
        return E_FAIL;
    for( DWORD i=0; i<50; i++ )
    {
        FLOAT theta = (2*D3DX_PI*i)/(50-1);
        pVertices[2*i+0].position = D3DXVECTOR3( sinf(theta),-1.0f, cosf(theta) );
        pVertices[2*i+0].normal   = D3DXVECTOR3( sinf(theta), 0.0f, cosf(theta) );
        pVertices[2*i+1].position = D3DXVECTOR3( sinf(theta), 1.0f, cosf(theta) );
        pVertices[2*i+1].normal   = D3DXVECTOR3( sinf(theta), 0.0f, cosf(theta) );
    }
    g_pVB->Unlock();

    return S_OK;
}


//-----------------------------------------------------------------------------
// Desc: 设置材质和灯光
//-----------------------------------------------------------------------------
VOID SetupLights()
{
	//设置材料属性, 只反射红光分量和绿光分量, 整体上看该物体材料反射黄色光
    D3DMATERIAL9 mtrl;
    ZeroMemory( &mtrl, sizeof(D3DMATERIAL9) );

	mtrl.Ambient.r = 1.0f;
	mtrl.Ambient.g = 1.0f;
	mtrl.Ambient.b = 0.0f;
	mtrl.Ambient.a = 1.0f;

    mtrl.Diffuse.r = 1.0f;
    mtrl.Diffuse.g = 1.0f;
    mtrl.Diffuse.b = 0.0f;
    mtrl.Diffuse.a = 0.5f;

	mtrl.Specular.r = 1.0f;
	mtrl.Specular.g = 1.0f;
	mtrl.Specular.b = 1.0f;
	mtrl.Specular.a = 1.0f;

    g_pd3dDevice->SetMaterial( &mtrl );

	//设置一号光源为方向光，颜色为绿色
    D3DXVECTOR3 vecDir;
    D3DLIGHT9 light1;
    ZeroMemory( &light1, sizeof(D3DLIGHT9) );
    light1.Type       = D3DLIGHT_DIRECTIONAL;
    light1.Ambient.r  = 0.0f;
    light1.Ambient.g  = 1.0f;
    light1.Ambient.b  = 0.0f;
    vecDir = D3DXVECTOR3(-10, 0 ,10); //方向光方向
    
	D3DXVec3Normalize( (D3DXVECTOR3*)&light1.Direction, &vecDir );
    g_pd3dDevice->SetLight( 0, &light1 );

	//二号光源为点光源，颜色为红色
    D3DXVECTOR3  vecPos2;
    D3DLIGHT9 light2;
    ZeroMemory( &light2, sizeof(D3DLIGHT9) );
    light2.Type       = D3DLIGHT_POINT;  
    light2.Diffuse.r  = 0.5f;
    light2.Diffuse.g  = 0.0f;
    light2.Diffuse.b  = 0.0f;

    light2.Position= D3DXVECTOR3(10*sinf(timeGetTime()/350.0f) ,
                         0,
						 10*cosf(timeGetTime()/350.0f) );

    light2.Range        = 100.0f;
	light2.Attenuation0 = 1.0f;
    g_pd3dDevice->SetLight( 1, &light2 );

	//四号光源为点光源，颜色为红色
	D3DXVECTOR3  vecPos4;
	D3DLIGHT9 light4;
	ZeroMemory( &light4, sizeof(D3DLIGHT9) );
	light4.Type       = D3DLIGHT_POINT;  
	light4.Ambient.r  = 0.f;
	light4.Ambient.g  = 0.5f;
	light4.Ambient.b  = 0.0f;

	light4.Position= D3DXVECTOR3(10*sinf(timeGetTime()/350.0f) ,
		0,
		10*cosf(timeGetTime()/350.0f) );

	light4.Range        = 100.0f;
	light4.Attenuation0 = 1.0f;
	g_pd3dDevice->SetLight( 3, &light4 );

	//三号光源为方向光,颜色为绿色, *镜面反射*
	D3DXVECTOR3 vecDir3;
    D3DLIGHT9 light3;
    ZeroMemory( &light3, sizeof(D3DLIGHT9) );
    light3.Type       = D3DLIGHT_DIRECTIONAL; 
	light3.Specular.r  = 0.0f;
	light3.Specular.g  = .0f;
	light3.Specular.b  = 1.0f;
	light3.Specular.a  = 1.0f;
    vecDir3 = D3DXVECTOR3(-10,0,10);
    
	D3DXVec3Normalize( (D3DXVECTOR3*)&light3.Direction, &vecDir3 );
    g_pd3dDevice->SetLight( 2, &light3 );

	//设置一定的环境光
	g_pd3dDevice->SetRenderState( D3DRS_AMBIENT, 0x00505050);
}

效果：

1. 只有D3DFVF_DIFFUSE， 顶点呈现制定颜色。

2. 有D3DFVF_DIFFUSE，物体材质全部设为1.f

    a. 只开全局环境光，全局环境光将D3DFVF_DIFFUSE值覆盖

    b. 全局环境光、单个光源的相同光照模型的光照值累加覆盖

    c. 不含全局环境光，相同光源的不同光照模型的光照值累加覆盖

    d. 不含全局环境光，不同光源的不同光照模型的光照值累计覆盖

注： a. 点光源：有位置，需要为之设置关照范围以及关照的衰减率。点光源没有方向属性，而在进行漫反射和镜面反射光照计算时需要使用光线的方向向量，原因是点光源

             向四周发射光线，显然方向不固定，因此就不可能在光源属性中像方向光那样用一个方向向量表示，而在具体计算某个顶点的光照颜色时，根据顶点和光源的位置，

             不难计算出光线的方向。

         b. 光照的矢量以世界坐标为参照，而物体的顶点法向量以三角形的顶点顺序所构造的法向量为标准。

结论： 当不同的光源的不同光照模型进行累加，物体最终所呈现出来的颜色比例有材质决定。但是总的颜色值还是为各种光源的不同光照模型的总和。