S3 Texture Compression

Software theme

A group of lossy texture compression algorithms originally by S3 Graphics included in DirectX 6.0, OpenGL 1.3, and subsequent versions.


Alternate names: S3TC, DXTn, DXTC, GL_EXT_texture_compression_s3tc, GL_EXT_texture_compression_dxt1

The first video game about S3 Texture Compression was released in 2004.

DirectX 6 seems to require that hardware supports DXTC while OpenGL 1.3 has extensions for S3TC and DXT1. GL_ARB_texture_compression is a generic interface for all texture compression formats (e.g. FXT1), not just S3TC (GL_EXT_texture_compression_s3tc), though it probably uses S3TC by default nowadays.
S3 Texture Compression and derivative compression schemes are patented (software patent in the USA: US6775417) and present a licensing problem for proprietary games when they are used in conjuncture with non-proprietary operating systems and software. Some companies, such as AMD and Intel, have chosen hardware designs that (apparently) minimize licensing fees for the applicable patents but require keeping the derivative intellectual property closed. Software developers are often unaware of S3TC licensing as the fees apply to manufactures of DirectX compatible 3D acceleration cards and OpenGL compatible chips. Thus, developers often use S3TC without knowing or without concern of this limit to their consumer base.

To date, the patent is not valid outside the USA. A Debian based solution for anyone not bound by the patent are the libtxc-dxtn-dev and libtxc-dxtn0 packages.
Apparently during the HTC-Apple legal battles in 2011, the S3TC patent was pronounced invalid. However, only Intel and X.org have acted on this news. Google seems to be skeptical that this news is true or that the patent is in fact invalid.

S2TC - A patent free alternative
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