Handling the Creation of Volume Textures
DirectX 8.0 introduces a new surface capability bit DDSCAPS2_VOLUME. This flag is set in the ddsCapsEx.dwCaps2 field of the surface's DD_SURFACE_MORE structure. In the DdCreateSurface and D3dCreateSurfaceEx callbacks the depth of the volume texture can be found in the low word of the dwCaps4 field of the extended surface capabilities (ddsCapsEx) of the surface's DD_SURFACE_MORE structure. The driver should return the "slice pitch" (that is, the number of bytes to add to move from one 2D slice of the volume to the next) of the volume texture in the dwBlockSizeY field of the surface global structure.