DDS File Layout for Volume Textures
A volume texture is an extension of the standard texture for Microsoft?DirectX?9.0. x, and can be defined with or without mipmaps. If a file contains a volume texture, DDSCAPS_COMPLEX, DDSCAPS2_VOLUME, DDSD_DEPTH, and dwDepth should be set. For volumes without mipmaps, each depth slice is written to the file in order. If mipmaps are included, all depth slices for a given mipmap level are written together, with each level containing half as many slices as the previous level with a minimum of 1. Volume textures do not support DXTn compression as of DirectX 9.0.
For example, a 64-by-64-by-4 volume map, a pixel format of R8G8B8 (3 bytes per pixel), and all mipmap levels would contain the following:
| "DDS ", |
| (64, 64, 4), |
| (pitch=768), | 128 bytes |
| (pixel format=R8G8B8, bitcount=24), |
| (mipmapcount=7), |
| (DEPTH, TEXTURE, PITCH, COMPLEX, MIPMAP, VOLUME, RGB) |
| 64-by-64 slice 1 of 4 main image. | 12288 bytes |
| 64-by-64 slice 2 of 4 main image. | 12288 bytes |
| 64-by-64 slice 3 of 4 main image. | 12288 bytes |
| 64-by-64 slice 4 of 4 main image. | 12288 bytes |
| 32-by-32 slice 1 of 2 mipmap image. | 3072 bytes |
| 32-by-32 slice 2 of 2 mipmap image. | 3072 bytes |
| 16-by-16 slice 1 of 1 mipmap image. | 768 bytes |
| 8-by-8 slice 1 of 1 mipmap image. | 192 bytes |
| 4-by-4 slice 1 of 1 mipmap image. | 48 bytes |
| 2-by-2 slice 1 of 1 mipmap image. | 12 bytes |
| 1-by-1 slice 1 of 1 mipmap image. | 4 bytes |