Physically based rendering

Source: Wikipedia, the free encyclopedia.
diamond plate texture rendered close-up using physically based rendering principles. Microfacet abrasions cover the material, giving it a rough, realistic look even though the material is a metal. Specular highlights are high and realistically modeled at the appropriate edge of the tread using a normal map
.

Physically based rendering (PBR) is a computer graphics approach that seeks to render images in a way that models the lights and surfaces with optics in the real world. It is often referred to as "Physically Based Lighting" or "Physically Based Shading". Many PBR pipelines aim to achieve photorealism. Feasible and quick approximations of the bidirectional reflectance distribution function and rendering equation are of mathematical importance in this field. Photogrammetry may be used to help discover and encode accurate optical properties of materials. PBR principles may be implemented in real-time applications using Shaders or offline applications using ray tracing or path tracing.

History

Starting in the 1980s, a number of rendering researchers worked on establishing a solid theoretical basis for rendering, including physical correctness. Much of this work was done at the Cornell University Program of Computer Graphics; a 1997 paper from that lab[1] describes the work done at Cornell in this area to that point.

"Physically Based Shading" was introduced by

Yoshiharu Gotanda during the course Physically-Based Shading Models in Film and Game Production at the SIGGRAPH 2010. And followed by the course Physically Based Shading in Theory and Practice organised by Stephen Hill and Stephen McAuley
between 2012 and 2020.

The phrase "Physically Based Rendering" was more widely popularized by

special effects.[2] The book is now in its fourth edition.[3]

The first successful, yet partial implementation of physically-based rendering in a video game can be found in the 2013 title Remember Me, that despite being built on a game engine not natively supporting this technology (Unreal Engine 3) was properly modified to accommodate this feature.[4] Despite being a moderate approach to PBR, its accuracy has been further refined with posterior titles such as Ryse: Son of Rome and Killzone Shadow Fall, released on the same year, until the current state of PBR advancements in the 2020s.[5][6]

Process

opaque surface, more than just diffuse light is reflected from the brighter side of the material, creating small highlights, because "everything is shiny" in the physically-based rendering model of the real world. Tessellation is used to generate an object mesh from a heightmap and normal map
, creating greater detail.

PBR is, as Joe Wilson puts it, "more of a concept than a strict set of rules"

specular highlights and cavities
resulting from smoothness or roughness in addition to traditional specular or reflectivity maps.

Surfaces

PBR often utilize Bidirectional scattering distribution functions to calculate the visible light reflected at a given point on surfaces. Common techniques use approximations and simplified models that try to fit approximate models to more accurate data from other more time consuming methods or laboratory measurements (such as those of a gonioreflectometer).

As described by researcher Jeff Russell of Marmoset, a surface-focused physically based rendering pipeline may also focus on the following areas of research:[6]

Volumes

PBR is also often extended into volume renderings, with areas of research like:

Application

Thanks to high performance and low costs of modern hardware[8] it has become feasible to use PBR not only for industrial but also entertainment purposes wherever photorealistic images are desired, such as video games or movie making.[2] Today's mid to high-end hardware is capable of producing and rendering PBR content and there exists a market of easy-to-use software that allows designers of all experience levels to take advantage of physically based rendering methods, such as:

A typical application provides an intuitive

GLSL
, though increasingly node-based material editors that allow a graph-based workflow with native support for important concepts such as light position, levels of reflection and emission and metallicity, and a wide range of other math and optics functions are replacing hand-written shaders for all but the most complex applications.

See also

References

  1. doi:10.1145/310930.310970. Archived
    (PDF) from the original on 24 September 2018. Retrieved 27 November 2017.
  2. ^
    ISBN 9780080538969
    .
  3. ISBN 9780262048026
    .
  4. ^ a b Wilson, Joe. "Physically Based Rendering – And You Can Too!" Retrieved on 12 Jan 2017.
  5. ^ a b "Point Clouds". Sketchfab Help Center. Retrieved 2018-05-29.
  6. ^ a b Russell, Jeff, "PBR Theory". Retrieved on 20 August 2019.
  7. ^ Hable, John . "Everything Is Shiny" Archived 2016-12-05 at the Wayback Machine. Retrieved on 14 November 2016.
  8. ^ Kam, Ken. "How Moore's Law Now Favors Nvidia Over Intel". Forbes. Retrieved 2018-05-29.
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