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DDS Cube Map Example

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For cubic environment maps, one or more faces of a cube are written to the file, using either uncompressed or compressed formats, and all faces must be the same size. Each face can have mipmaps defined, although all faces must have the same number of mipmap levels. If a file contains a cube map, DDSCAPS_COMPLEX, DDSCAPS2_CUBEMAP, and one or more of DSCAPS2_CUBEMAP_POSITIVEX/Y/Z and/or DDSCAPS2_CUBEMAP_NEGATIVEX/Y/Z should be set. The faces are written in the order: positive x, negative x, positive y, negative y, positive z, negative z, with any missing faces omitted. Each face is written with its main image, followed by any mipmap levels.

For example, a 256-by-256 cube map with positive x, negative y, and positive z faces, a pixel format of DXT1, and all mipmap levels would contain the following:

DDS Components # Bytes
header 128
256-by-256 positive x main image 32768
128-by-128 positive x mipmap image 8192
64-by-64 positive x mipmap image 2048
32-by-32 positive x mipmap image 512
16-by-16 positive x mipmap image 128
8-by-8 positive x mipmap image 32
4-by-4 positive x mipmap image 8
2-by-2 positive x mipmap image 8
1-by-1 positive x mipmap image 8
repeat the previous 9 layers for the y mipmap image 43704
repeat the previous 9 layers for the z mipmap image 43704

 

Starting with DirectX 8, a cube map is stored with all faces defined.

DXGI Cube Maps

Cubic environment maps in Direct3D 10.x and Direct3D 11 are equivalent to a 2D texture array with 6 images, and can be stored in DDS files as such. With Direct3D 10.1 and Direct3D 11, the hardware can also support arrays of cubemaps which are themselves 2D texture arrays with a multiple of 6 images (6, 12, 18, 24, etc.).

For example, here is a 256-by-256 cubemap with mipmap levels stored in a BC6H format as a 2D texture array:

DDS Components # Bytes
header (FourCC of "DX10") 128
extended header (DXGI format set to 95 [DXGI_FORMAT_BC6H_UF16], dimension value of 3 [D3Dxx_RESOURCE_DIMENSION_TEXTURE2D], array size of 6, misc flags of 0x4 [D3Dxx_RESOURCE_MISC_TEXTURECUBE]) 20
256-by-256 array entry 0 (positive x) main image 65536
128-by-128 array entry 0 (positive x) mipmap image 16384
64-by-64 array entry 0 (positive x) mipmap image 4096
32-by-32 array entry 0 (positive x) mipmap image 1024
16-by-16 array entry 0 (positive x) mipmap image 256
8-by-8 array entry 0 (positive x) mipmap image 64
4-by-4 array entry 0 (positive x) mipmap image 16
2-by-2 array entry 0 (positive x) mipmap image 16
1-by-1 array entry 0 (positive x) mipmap image 16
repeat the previous 9 layers for array entry 1 (negative x) mipmap image 87408
repeat the previous 9 layers for array entry 2 (positive y) mipmap image 87408
repeat the previous 9 layers for array entry 3 (negative y) mipmap image 87408
repeat the previous 9 layers for array entry 4 (positive z) mipmap image 87408
repeat the previous 9 layers for array entry 5 (negative z) mipmap image 87408

 

Programming Guide for DDS