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Texture Block Compression in Direct3D 11

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Block Compression (BC) support for textures has been extended in Direct3D 11 to include the BC6H and BC7 algorithms. BC6H supports high-dynamic range color source data, and BC7 provides better-than-average quality compression with less artifacts for standard RGB source data.

For more specific information about block compression algorithm support prior to Direct3D 11, including support for the BC1 through BC5 formats, see Block Compression (Direct3D 10).

Note about File Formats: The BC6H and BC7 texture compression formats use the DDS file format for storing the compressed texture data. For more information, see the Programming Guide for DDS for details.

Block Compression Formats Supported in Direct3D 11

Source data Minimum required data compression resolution Recommended format Minimum supported feature level
Three-channel color with alpha channel Three color channels (5 bits:6 bits:5 bits), with 0 or 1 bit(s) of alpha BC1 Direct3D 9.1
Three-channel color with alpha channel Three color channels (5 bits:6 bits:5 bits), with 4 bits of alpha BC2 Direct3D 9.1
Three-channel color with alpha channel Three color channels (5 bits:6 bits:5 bits) with 8 bits of alpha BC3 Direct3D 9.1
One-channel color One color channel (8 bits) BC4 Direct3D 10
Two-channel color Two color channels (8 bits:8 bits) BC5 Direct3D 10
Three-channel high dynamic range (HDR) color Three color channels (16 bits:16 bits:16 bits) in "half" floating point* BC6H Direct3D 11
Three-channel color, alpha channel optional Three color channels (4 to 7 bits per channel) with 0 to 8 bits of alpha BC7 Direct3D 11

*"Half" floating point is a 16 bit value that consists of an optional sign bit, a 5 bit biased exponent, and a 10 or 11 bit mantissa.

BC1, BC2, and B3 Formats

The BC1, BC2, and BC3 formats are equivalent to the Direct3D 9 DXTn texture compression formats, and are the same as the corresponding Direct3D 10 BC1, BC2, and BC3 formats. Support for these three formats is required by all feature levels (D3D_FEATURE_LEVEL_9_1, D3D_FEATURE_LEVEL_9_2, D3D_FEATURE_LEVEL_9_3, D3D_FEATURE_LEVEL_10_0, D3D_FEATURE_LEVEL_10_1, and D3D_FEATURE_LEVEL_11_0).

Block compression format DXGI format Direct3D 9 equivalent format Bytes per 4x4 pixel block
BC1 DXGI_FORMAT_BC1_UNORM, DXGI_FORMAT_BC1_UNORM_SRGB, DXGI_FORMAT_BC1_TYPELESS D3DFMT_DXT1, FourCC="DXT1" 8
BC2 DXGI_FORMAT_BC2_UNORM, DXGI_FORMAT_BC2_UNORM_SRGB, DXGI_FORMAT_BC2_TYPELESS D3DFMT_DXT2*, FourCC="DXT2", D3DFMT_DXT3, FourCC="DXT3" 16
BC3 DXGI_FORMAT_BC3_UNORM, DXGI_FORMAT_BC3_UNORM_SRGB, DXGI_FORMAT_BC3_TYPELESS D3DFMT_DXT4*, FourCC="DXT4", D3DFMT_DXT5, FourCC="DXT5" 16

*These compression schemes (DXT2 and DXT4) make no distinction between the Direct3D 9 pre-multiplied alpha formats and the standard alpha formats. This distinction must be handled by the programmable shaders at render time.

BC4 and BC5 Formats

Block compression format DXGI format Direct3D 9 equivalent format Bytes per 4x4 pixel block
BC4 DXGI_FORMAT_BC4_UNORM, DXGI_FORMAT_BC4_SNORM, DXGI_FORMAT_BC4_TYPELESS FourCC="ATI1" 8
BC5 DXGI_FORMAT_BC5_UNORM, DXGI_FORMAT_BC5_SNORM, DXGI_FORMAT_BC5_TYPELESS FourCC="ATI2" 16

BC6H Format

For more detailed information about this format, see the BC6H Format documentation.

Block compression format DXGI format Direct3D 9 equivalent format Bytes per 4x4 pixel block
BC6H DXGI_FORMAT_BC6H_UF16, DXGI_FORMAT_BC6H_SF16, DXGI_FORMAT_BC6H_TYPELESS N/A 16

The BC6H format can select different encoding modes for each 4x4 pixel block. A total of 14 different encoding modes are available, each with slightly different trade-offs in the resulting visual quality of the displayed texture. The choice of modes allows for fast decoding by the hardware with the quality level selected or adapted according to the source content, but it also greatly increases the complexity of the search space.

BC7 Format

For more detailed information about this format, see the BC7 Format documentation.

Block compression format DXGI format Direct3D 9 equivalent format Bytes per 4x4 pixel block
BC7 DXGI_FORMAT_BC7_UNORM, DXGI_FORMAT_BC7_UNORM_SRGB, DXGI_FORMAT_BC7_TYPELESS N/A 16

The BC7 format can select different encoding modes for each 4x4 pixel block. A total of 8 different encoding modes are available, each with slightly different trade-offs in the resulting visual quality of the displayed texture. The choice of modes allows for fast decoding by the hardware with the quality level selected or adapted according to the source content, but it also greatly increases the complexity of the search space.

In this section

Topic Description
BC6H Format
 The BC6H format is a texture compression format designed to support high-dynamic range (HDR) color spaces in source data.
BC7 Format
 The BC7 format is a texture compression format used for high-quality compression of RGB and RGBA data.
BC7 Format Mode Reference
 This documentation contains a list of the 8 block modes and bit allocations for BC7 texture compression format blocks.

Block Compression (Direct3D 10)

Textures