AMD TressFX is a software library which provides for advanced

simulation A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in ...

and rendering of hair, fur, and grass to be processed by the GPU. The initial library was written to perform well on AMD's GCN-based products. Version 3 was released on January 26, 2016, and works solely with

Direct3D 11 Direct3D is a graphics application programming interface (API) for Microsoft Windows. Part of DirectX, Direct3D is used to render three-dimensional graphics in applications where performance is important, such as games. Direct3D uses hardware a ...

and utilizes

DirectCompute Microsoft DirectCompute is an application programming interface (API) that supports running compute kernels on general-purpose computing on graphics processing units on Microsoft's Windows Vista, Windows 7 and later versions. DirectCompute is part ...

. A competing solution offered by

Nvidia Nvidia Corporation ( ) is an American multinational corporation and technology company headquartered in Santa Clara, California, and incorporated in Delaware. Founded in 1993 by Jensen Huang (president and CEO), Chris Malachowsky, and Curti ...

is HairWorks which is part of their Nvidia GameWorks suite and is proprietary in nature. Released as part of GPUOpen AMD TressFX is

free and open-source software Free and open-source software (FOSS) is software available under a license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term encompassing free ...

subject to the

MIT License The MIT License is a permissive software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts very few restrictions on reuse and therefore has high license compatibility. Unl ...

Motivations for development and origins

Traditionally, hair representation in video games has been sub-par for several reasons. For short hair (especially on male characters), hair has often been represented by a detailed

texture Texture may refer to: Science and technology * Image texture, the spatial arrangement of color or intensities in an image * Surface texture, the smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface c ...

on a character's skeleton. This makes it difficult to represent hair styles that are not pressed flat against the skull. Longer hair is often represented as a texture on a moving part of a skeleton and thus moves as a multi-jointed appendage. While this hair has more movement than the former, the movement is usually physically unrealistic – the hair moves as one body and movement is very often under or over damped. In order to overcome this, AMD developed TressFX Hair. TressFX Hair models each of potentially thousands of strands of hair individually with dozens of links per strand of hair. Each strand reacts to different physical forces such as

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

inertia Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

, and the movement of a character's head. This allows the hair to move in a much more physically realistic manner. Because simulating thousands of strands of hair is much more computationally intense than displaying a texture over a character's skeleton, the impact of TressFX Hair on game performance and frame rates may not be trivial. High performance video cards may have enough resources available that the extra effort of rendering hair may produce negligible or acceptable frame rate losses. Conversely, older video cards may spend a large proportion of each frame's render time rendering hair, and this can noticeably reduce game performance. Of course, performance is interrelated with other game settings, resolution, the number of objects with hair to be rendered in the screen, amount of hair per object, and distance from the object.

Versions

Version 1.0

TressFX Hair 1.0 was AMD's first release of this software in 2013. Version 1.0 only offered support for hair and not fur or grass. The first game to use TressFX Hair was the 2013 game ''

Tomb Raider ''Tomb Raider'', known as ''Lara Croft: Tomb Raider'' from 2001 to 2008, is a media franchise that originated with an Action-adventure game, action-adventure video game series created by British video game developer Core Design. The franchise i ...

''.

Version 2.0

Version 2.0 offers many improvements upon version 1.0 such as: *Continuous Level of detail (LOD) is designed to improve performance by dynamically adjusting visual detail as TressFX-enabled objects move towards and away from the player's point of view. This is done by rendering fewer hairs when far away from an object but making each hair thicker, thus reducing

computational A computation is any type of arithmetic or non-arithmetic calculation that is well-defined. Common examples of computation are mathematical equation solving and the execution of computer algorithms. Mechanical or electronic devices (or, historic ...

time but maintaining the same look and

aesthetic Aesthetics (also spelled esthetics) is the branch of philosophy concerned with the nature of beauty and taste, which in a broad sense incorporates the philosophy of art.Slater, B. H.Aesthetics ''Internet Encyclopedia of Philosophy,'' , acces ...

. *New functionality to support rendering for grass and fur in addition to hair. *Hairs are arranged in groups. Hair naturally groups together on a person's head. Renderings produced by TressFX 1.0 however did not do this, and so the hair looks unnaturally separated. *Gravity can be changed on the hair. For example, when swimming hair should be neutrally buoyant and should neither significantly sink nor float. In order to accomplish this, the gravity of the hair can be set to 0. *Improved efficiency with many light sources and

shaders In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the rendering of a 3D scene—a process known as '' shading''. Shaders have evolved to perform a variety of sp ...

via deferred rendering. *Superior self-shadowing for better depth and texture in the hair. *Even more robust scalability across GPUs of varying performance envelopes (vs. TressFX 1.0). * Modular code and porting documentation. *Stretchiness now respects the

laws of physics Scientific laws or laws of science are statements, based on repeated experiments or observations, that describe or predict a range of natural phenomena. The term ''law'' has diverse usage in many cases (approximate, accurate, broad, or narrow) ...

Version 3.0

The first game confirmed to use TressFX 3.0 is '' Deus Ex: Mankind Divided''.

Version 4.0

Version 4.0 of TressFX was released on the 20. April 2018 and brought a wide variety of improvements including DirectX 12 support. This release also focused on being much easier to import into existing rendering frameworks.

Version 4.1

This version was released on the 20 January 2020. It includes some performance improvements, but mostly is focused on better integration in existing rendering frameworks. An integration into the Epic Games Unreal Engine 4.22 is provided including detailed documentation.

PureHair

PureHair is a version of TressFX modified by

Square Enix is a Japanese Multinational corporation, multinational holding company, video game publisher and entertainment conglomerate. It releases role-playing video game, role-playing game franchises, such as ''Final Fantasy'', ''Dragon Quest'', and '' ...

for use in '' Rise of the Tomb Raider''.

References

External links

AMD page on TressFX
{{AMD graphics AMD software Free software programmed in C++ Software using the MIT license