Cube maps can be mipmapped. To create a mipmapped cube map, set the Levels parameter of the IDirect3DDevice8::CreateCubeTexture method to the number of levels that you want. You can envision the topography of these surfaces as shown in the following graphic.

Applications that create mipmapped cubic environment maps can access each face by calling the IDirect3DCubeTexture8::GetCubeMapSurface method. Start by setting the appropriate value from the D3DCUBEMAP_FACES enumerated type, as discussed in Accessing Cubic Environment Map Faces. Next, select the level to retrieve by setting the Level parameter to the mipmap level that you want. Remember that 0 corresponds with the top-level image.

Texture coordinates that index a cubic environment map aren't simple u, v style coordinates, as used when standard textures are applied. In fact, cubic environment maps don't use texture coordinates at all. In place of a set of texture coordinates, cubic environment maps require a 3-D vector. You must take care to specify a proper vertex format. In addition to telling the system how many sets of texture coordinates your application uses, you must provide information about how many elements are in each set. Microsoft® Direct3D® offers the D3DFVF_TEXCOORDSIZEn set of macros for this purpose. These macros accept a single parameter, identifying the index of the texture coordinate set for which the size is being described. In the case of a 3-D vector, you include the bit pattern created by the D3DFVF_TEXCOORDSIZE3 macro. The following code example shows how this macro is used.

/*
 * Create a flexible vertex format descriptor for a vertex that 
 * contains a position, normal, and one set of 3-D texture 
 * coordinates.
 */
DWORD dwFVF = D3DFVF_XYZ | D3DFVF_NORMAL | D3DFVF_TEX1 | D3DFVF_TEXCOORDSIZE3(0); 

In some cases, such as diffuse light mapping, you use the camera-space vertex normal for the vector. In other cases, like specular environment mapping, you use a reflection vector. Because transformed vertex normals are widely understood, the information here concentrates on computing a reflection vector.

Computing a reflection vector on your own requires understanding of the position of each vertex, and of a vector from the viewpoint to that vertex. Direct3D can automatically compute the reflection vectors for your geometry. Using this feature saves memory because you don't need to include texture coordinates for the environment map. It also reduces bandwidth and, in the case of a TnLHAL Device, it can be significantly faster than the computations that your application can make on its own. To use this feature, in the texture stage that contains the cubic environment map, set the D3DTSS_TEXCOORDINDEX texture stage state to a combination of the D3DTSS_TCI_CAMERASPACEREFLECTIONVECTOR flag and the index of a texture coordinate set. In some situations, like diffuse light mapping, you might use the D3DTSS_TCI_CAMERASPACENORMAL flag, which causes the system to use the transformed, camera-space, vertex normal as the addressing vector for the texture. The index is only used by the system to determine the wrapping mode for the texture.

The following code example shows how this value is used.

/*
 * The m_d3dDevice variable is a valid pointer
 * to an IDirect3DDevice8 interface.
 *
 * Automatically generate texture coordinates for stage 2.
 * This assumes that stage 2 is assigned a cube map.
 * Use the wrap mode from the texture coordinate set at index 1.
 */
m_d3dDevice->SetTextureStageState( 2, D3DTSS_TEXCOORDINDEX,
                                   D3DTSS_TCI_CAMERASPACEREFLECTIONVECTOR | 1);