FXT1

Last updated

FXT1 is a texture compression scheme for 3D graphics, invented by the hardware vendor 3dfx Interactive and offered as an open source rival standard to S3TC in September 1999, a year after S3TC had been adopted by Microsoft as part of DirectX. Limited vendor hardware support has been a barrier to its acceptance. [1] [2] [3] Notably, despite being open source, FXT1 was not adopted by Nintendo for the GameCube, nor by Sony for the PlayStation 3, in both cases losing out to the established S3TC standard. Another possible reason for its lack of adoption is that the CC_MIXED mode (see below) probably infringes the S3TC patent ( US 5956431  System and method for fixed-rate block-based image compression with inferred pixel values).

Contents

Four different compression algorithms are used by FXT1, chosen at a block level to optimize visual quality. [1] Having to select an optimal path for each texture ensured FXT1 was relatively slow at compression, making it unsuitable for real-time compression in applications. [2]

The original white paper did not follow well-known scientific rules, being actually a commercial presentation. The lack of theoretical guidance from the inventors might have been the cause of badly optimized compression scheme selection code, and despite potentially better performance due to four available compression schemes instead of one (as in S3TC), FXT1 did not show any quality improvements to S3TC, being inferior to it in most test cases.

In hindsight, FXT1 might have been more successful if 3dfx spent more effort examining optimization [2] of the CC_MIXED [1] compression mode, more similar to S3TC, [2] and dropped the other three codecs from the standard.[ citation needed ] 3dfx was subsequently taken over by Nvidia [4] [5] who have continued to support S3TC as their preferred compression tool. [6]

Compression algorithms

Four different compression algorithms are set out in the original white paper [1] [2] :

CC_MIXED (similar to other S3TC)
A 4x4 texel block is represented by two bits-per-texel for opaque textures. Additionally, each block has two 16-bit colors stored in an RGB 565 format. The two RGB 565 colors and two additional colors (created by interpolating between the two RGB 565 colors) form the primary colors for this texel block and its associated four color lookup table. A 2-bit index is used to determine which color from the lookup table will be used for each texel in the 4x4 block. Transparent textures are created by making one of the four colors transparent.
CC_HI (best for spatial resolution)
A 4×8 texel block is represented by three bits-per-texel for opaque and transparent textures. Each block stores two 15-bit colors in an RGB 555 format. The two RGB 555 colors and five additional colors (created by interpolating between the two RGB 555 colors) form the primary colors for this texel block. Additionally, an eighth color is defined to be the transparent color. A 3-bit index is used to determine which color from the 8-entry lookup table will be used for each texel in the 4x8 block.
CC_CHROMA (good at complex color areas)
A 4×8 texel block is represented by two bits-per-texel for opaque textures. Each block stores four 15-bit colors in an RGB 555 format. All four colors are used directly with no interpolation to form a 4-entry lookup table. The 2-bit index assigned to each texel in the block is used to determine which of the four colors is assigned to each individual texel. Note that Colors4 only applies to opaque textures, as it does not support transparency.
CC_ALPHA (gives the best control over complex alpha transparencies at four bits-per-texel)
A 4×8 texel block is represented by two bits-per-texel for opaque and transparent textures. Each block stores three 20-bit colors stored in a 5555 format. The first and second 20-bit colors are used for the primary colors of the left 4x4 block, while the second and third colors are used for the primary colors of the right 4×4 block. Two additional colors are created in each block by interpolating between the two primary colors for that block. A 2-bit index is assigned to each texel in the block and a lookup table is used to determine which color is applied to each texel.

See also

Related Research Articles

<span class="mw-page-title-main">Alpha compositing</span> Operation in computer graphics

In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate passes or layers and then combine the resulting 2D images into a single, final image called the composite. Compositing is used extensively in film when combining computer-rendered image elements with live footage. Alpha blending is also used in 2D computer graphics to put rasterized foreground elements over a background.

The BMP file format or bitmap, is a raster graphics image file format used to store bitmap digital images, independently of the display device, especially on Microsoft Windows and OS/2 operating systems.

<span class="mw-page-title-main">Smacker video</span> Digital video file format

Smacker video is a video file format developed by Epic Games Tools, and primarily used for full-motion video in video games. Smacker uses an adaptive 8-bit RGB palette. RAD's format for video at higher color depths is Bink Video. The Smacker format specifies a container format, a video compression format, and an audio compression format. Since its release in 1994, Smacker has been used in over 2300 games. Blizzard used this format for the cinematic videos seen in its games Warcraft II, StarCraft and Diablo I.

sRGB Standard RGB color space

sRGB is a standard RGB color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission (IEC) as IEC 61966-2-1:1999. sRGB is the current defined standard colorspace for the web, and it is usually the assumed colorspace for images that are neither tagged for a colorspace nor have an embedded color profile.

In computer graphics, texture filtering or texture smoothing is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels.

<span class="mw-page-title-main">Voodoo 5</span> Graphics card line

The Voodoo 5 was the last and most powerful graphics card line that was released by 3dfx Interactive. All members of the family were based upon the VSA-100 graphics processor. Only the single-chip Voodoo 4 4500 and dual-chip Voodoo 5 5500 made it to market.

S3 Texture Compression (S3TC) is a group of related lossy texture compression algorithms originally developed by Iourcha et al. of S3 Graphics, Ltd. for use in their Savage 3D computer graphics accelerator. The method of compression is strikingly similar to the previously published Color Cell Compression, which is in turn an adaptation of Block Truncation Coding published in the late 1970s. Unlike some image compression algorithms, S3TC's fixed-rate data compression coupled with the single memory access made it well-suited for use in compressing textures in hardware-accelerated 3D computer graphics. Its subsequent inclusion in Microsoft's DirectX 6.0 and OpenGL 1.3 led to widespread adoption of the technology among hardware and software makers. While S3 Graphics is no longer a competitor in the graphics accelerator market, license fees have been levied and collected for the use of S3TC technology until October 2017, for example in game consoles and graphics cards. The wide use of S3TC has led to a de facto requirement for OpenGL drivers to support it, but the patent-encumbered status of S3TC presented a major obstacle to open source implementations, while implementation approaches which tried to avoid the patented parts existed.

<span class="mw-page-title-main">S3 Savage</span> Line of PC graphics chipsets by S3

Savage was a product-line of PC graphics chipsets designed by S3.

Color digital images are made of pixels, and pixels are made of combinations of primary colors represented by a series of code. A channel in this context is the grayscale image of the same size as a color image, made of just one of these primary colors. For instance, an image from a standard digital camera will have a red, green and blue channel. A grayscale image has just one channel.

Microsoft Video 1 or MS-CRAM is an early lossy video compression and decompression algorithm (codec) that was released with version 1.0 of Microsoft's Video for Windows in November 1992. It is based on MotiVE, a vector quantization codec which Microsoft licensed from Media Vision. In 1993, Media Vision marketed the Pro Movie Spectrum, an ISA board that captured video in both raw and MSV1 formats.

<span class="mw-page-title-main">Palette (computing)</span> In computer graphics, a finite set of available colors

In computer graphics, a palette is the set of available colors from which an image can be made. In some systems, the palette is fixed by the hardware design, and in others it is dynamic, typically implemented via a color lookup table (CLUT), a correspondence table in which selected colors from a certain color space's color reproduction range are assigned an index, by which they can be referenced. By referencing the colors via an index, which takes less information than needed to describe the actual colors in the color space, this technique aims to reduce data usage, including processing, transfer bandwidth, RAM usage, and storage. Images in which colors are indicated by references to a CLUT are called indexed color images.

In computing, indexed color is a technique to manage digital images' colors in a limited fashion, in order to save computer memory and file storage, while speeding up display refresh and file transfers. It is a form of vector quantization compression.

<span class="mw-page-title-main">Texture compression</span> Type of data compression

Texture compression is a specialized form of image compression designed for storing texture maps in 3D computer graphics rendering systems. Unlike conventional image compression algorithms, texture compression algorithms are optimized for random access.

PVRTC and PVRTC2 are a family of lossy, fixed-rate texture compression formats used in PowerVR's MBX, SGX and Rogue technologies. The PVRTC algorithm is documented in Simon Fenney's paper "Texture Compression using Low-Frequency Signal Modulation" that was presented at Graphics Hardware 2003.

Ericsson Texture Compression (ETC) is a lossy texture compression technique developed in collaboration with Ericsson Research in early 2005. It was originally developed under the name iPACKMAN and based on an earlier compression scheme called iPACKMAN.

<span class="mw-page-title-main">Color Cell Compression</span> Lossy color image compression algorithm

Color Cell Compression is a lossy image compression algorithm developed by Campbell et al., in 1986, which can be considered an early forerunner of modern texture compression algorithms, such as S3 Texture Compression and Adaptive Scalable Texture Compression. It is closely related to Block Truncation Coding, another lossy image compression algorithm, which predates Color Cell Compression, in that it uses the dominant luminance of a block of pixels to partition said pixels into two representative colors. The primary difference between Block Truncation Coding and Color Cell Compression is that the former was designed to compress grayscale images and the latter was designed to compress color images. Also, Block Truncation Coding requires that the standard deviation of the colors of pixels in a block be computed in order to compress an image, whereas Color Cell Compression does not use the standard deviation. Both algorithms, though, can compress an image down to effectively 2 bits per pixel.

Adaptive scalable texture compression (ASTC) is a lossy block-based texture compression algorithm developed by Jørn Nystad et al. of ARM Ltd. and AMD.

Apple Video is a lossy video compression and decompression algorithm (codec) developed by Apple Inc. and first released as part of QuickTime 1.0 in 1991. The codec is also known as QuickTime Video, by its FourCC RPZA and the name Road Pizza. When used in the AVI container, the FourCC AZPR is also used.

QuickTime Graphics is a lossy video compression and decompression algorithm (codec) developed by Apple Inc. and first released as part of QuickTime 1.x in the early 1990s. The codec is also known by the name Apple Graphics and its FourCC SMC. The codec operates on 8-bit palettized RGB data. The bit-stream format of QuickTime Graphics has been reverse-engineered and a decoder has been implemented in the projects XAnim and libavcodec.

References

  1. 1 2 3 4
  2. 1 2 3 4 5
  3. ↑ S2TC: A Possible Workaround For The S3TC Patent Situation Archived 2016-05-13 at the Wayback Machine on phoronix
  4. ↑ SEC filings, Form 8-K: Bankruptcy or receivership Archived August 27, 2017, at the Wayback Machine , updated October 21, 2002, retrieved August 28, 2024
  5. ↑ "3dfx Announces Three Major Initiatives To Protect Creditors and Maximize Shareholder Value". December 15, 2000. Archived from the original on April 5, 2001. Retrieved August 28, 2024.
  6. ↑ David Chrait (2015). "Using ASTC Texture Compression for Game Assets". developer.nvidia.com. Archived from the original on March 29, 2015. Retrieved August 28, 2024.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.