Adaptive scalable texture compression: Difference between revisions

Revision as of 16:56, 9 January 2013

Revision as of 21:56, 1 February 2013

Line 1:

'''Adaptive Scalable Texture Compression''' ('''ASTC''') is a [[lossy compression|lossy]] block-based [[texture compression]] [[algorithm]] developed by Jørn Nystad et al. of [[ARM_HoldingsARM Holdings|ARM Ltd.]]

Full details of ASTC were first presented publicly at the High Performance Graphics 2012 conference, in a paper by Olson et al. entitled "Adaptive Scalable Texture Compression"<ref>{{cite web|url=http://diglib.eg.org/EG/DL/WS/EGGH/HPG12/105-114.pdf.abstract.pdf;internal&action=action.digitallibrary.ShowPaperAbstract|title=Adaptive Scalable Texture Compression |publisher=HPG 2012 |date= |accessdate=2012-06-27}}</ref>

ASTC was adopted as an official extension for both OpenGL and OpenGL ES by the Khronos Group on 6 August 2012.<ref>{{cite web|url=http://www.khronos.org/news/press/khronos-releases-atsc-next-generation-texture-compression-specification|title=Khronos Releases ATSC Next-Generation 
Texture Texture Compression Specification|publisher=The Khronos Group Inc.|date=2012-08-06|accessdate=2012-08-06}}</ref>

== Overview ==

[[File:Original_Image_before_ASTC_compressionOriginal Image before ASTC compression.jpg|thumb|right|Example image prior to compression]][[File:Detail_of_ASTC_compressed_imageDetail of ASTC compressed image.png|thumb|right|Detail from example image, after compression at 4, 3.56 and 2 bits/pixel]]The method of compression is an evolution of [[Color Cell Compression]] with features including numerous closely spaced fractional bit rates, multiple color formats, support for High Dynamic Range (HDR) textures, and real 3D texture support.

[[File:Original_Image_before_ASTC_compression.jpg|thumb|right|Example image prior to compression]][[File:Detail_of_ASTC_compressed_image.png|thumb|right|Detail from example image, after compression at 4, 3.56 and 2 bits/pixel]]The method of compression is an evolution of [[Color Cell Compression]] with features including numerous closely spaced fractional bit rates, multiple color formats, support for High Dynamic Range (HDR) textures, and real 3D texture support.

The stated primary design goal for ASTC is to enable content developers to have better control over the space/quality tradeoff inherent in any lossy compression scheme. With ASTC, the ratio between adjacent bit rates is of the order of 25%, making it less expensive to increase quality for a given texture.

Line 19 ⟶ 18:

== Supported Color Formats ==

{| class="wikitable"

Line 46 ⟶ 44:

== 2D Block Footprints and Bit Rates ==

ASTC textures are compressed using a fixed block size of 128 bits, but with a variable block footprint ranging from 4x4 texels up to 12x12 texels. The available bit rates thus range from 8 bits per texel down to 0.89 bits per texel, with fine steps in between.

Line 88 ⟶ 85:

== 3D Block Footprints and Bit Rates ==

ASTC 3D textures are compressed using a fixed block size of 128 bits, as for 2D but with a variable block footprint ranging from 3x3x3 texels up to 6x6x6 texels. The available bit rates thus range from 4.74 bits per texel down to 0.59 bits per texel, with fine steps in between.