DirectX9 SDK Samples(5) Tutorial 5: Using Texture Maps

最新推荐文章于 2023-02-01 10:18:05 发布

翻译最新推荐文章于 2023-02-01 10:18:05 发布 · 806 阅读

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#textures #float #matrix #direct3d #generation #parameters

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本文介绍了如何在Direct3D中定义自定义顶点格式并添加纹理坐标，通过实现一个结构体来表示自定义顶点类型，并在创建圆柱几何体时设置纹理坐标。此外，详细解释了如何初始化屏幕几何形状，渲染场景时的纹理设置，以及使用Direct3D纹理坐标生成的注意事项。

Step 1 - Defining a Custom Vertex Format

// A structure for our custom vertex type. Texture coordinates were added.
struct CUSTOMVERTEX
{
    D3DXVECTOR3 position; // The position
    D3DCOLOR    color;    // The color
#ifndef SHOW_HOW_TO_USE_TCI
    FLOAT       tu, tv;   // The texture coordinates
#endif
};

// Custom flexible vertex format (FVF), which describes custom vertex structure
#ifdef SHOW_HOW_TO_USE_TCI
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE)
#else
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE|D3DFVF_TEX1)
#endif

设定FVF。

Step 2 - Initializing Screen Geometry

if( FAILED( D3DXCreateTextureFromFile( g_pd3dDevice, "Banana.bmp",
&g_pTexture ) ) )
return E_FAIL;

首先需要载入纹理。

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].color    = 0xffffffff;
#ifndef SHOW_HOW_TO_USE_TCI
        pVertices[2*i+0].tu       = ((FLOAT)i)/(50-1);
        pVertices[2*i+0].tv       = 1.0f;
#endif

        pVertices[2*i+1].position = D3DXVECTOR3( sinf(theta), 1.0f, cosf(theta) );
        pVertices[2*i+1].color    = 0xff808080;
#ifndef SHOW_HOW_TO_USE_TCI
        pVertices[2*i+1].tu       = ((FLOAT)i)/(50-1);
        pVertices[2*i+1].tv       = 0.0f;
#endif
}

然后在创建圆柱的代码中加入纹理坐标。

Step 3 - Rendering the Scene

g_pd3dDevice->SetTexture( 0, g_pTexture );

先设定纹理为第0层，固定管线中最多可以8层，也就是说序号为0到7。

接下来的一大段代码是关于设定纹理和纹理状态。

    // Setup texture. Using textures introduces the texture stage states, which
    //   govern how textures get blended together (in the case of multiple
    //   textures) and lighting information. In this case, you are modulating
    //   (blending) your texture with the diffuse color of the vertices.
    g_pd3dDevice->SetTexture( 0, g_pTexture );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_COLOROP,   D3DTOP_MODULATE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_DIFFUSE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAOP,   D3DTOP_DISABLE );

#ifdef SHOW_HOW_TO_USE_TCI
    // Note: To use Direct3D texture coordinate generation, use the stage state
    // D3DTSS_TEXCOORDINDEX, as shown below. In this example, you are using
    // the position of the vertex in camera space to generate texture
    // coordinates. The tex coord index (TCI) parameters are passed into a
    // texture transform, which is a 4x4 matrix that transforms the x,y,z
    // TCI coordinates into tu, tv texture coordinates.

    // In this example, the texture matrix is set up to 
    // transform the texture from (-1,+1) position coordinates to (0,1) 
    // texture coordinate space:
    //    tu =  0.5*x + 0.5
    //    tv = -0.5*y + 0.5
    D3DXMATRIXA16 mat;
    mat._11 = 0.25f; mat._12 = 0.00f; mat._13 = 0.00f; mat._14 = 0.00f;
    mat._21 = 0.00f; mat._22 =-0.25f; mat._23 = 0.00f; mat._24 = 0.00f;
    mat._31 = 0.00f; mat._32 = 0.00f; mat._33 = 1.00f; mat._34 = 0.00f;
    mat._41 = 0.50f; mat._42 = 0.50f; mat._43 = 0.00f; mat._44 = 1.00f;

    g_pd3dDevice->SetTransform( D3DTS_TEXTURE0, &mat );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_TEXTURETRANSFORMFLAGS, 
	    	D3DTTFF_COUNT2 );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_TEXCOORDINDEX, 
	    	D3DTSS_TCI_CAMERASPACEPOSITION );
#endif

老实说，我很奇怪为什么设置这么多参数，因为龙书中很多都用了默认参数。这里居然没有设定MIN、MAX和MIP，这我也感到相当奇怪。
宏定义中的代码是用到了TCI，我觉得平常是用不到了呃。