Physically based rendering: Difference between revisions

Revision as of 05:36, 15 July 2023

Revision as of 14:36, 22 September 2023

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{{short description|Computer graphics technique}}

[[File:Physically Based Rendering Sample 2.png|thumb|rightupright=1.2|A [[diamond plate]] texture rendered close-up using physically based rendering principles. [[Specular highlight#Microfacets|Microfacet]] abrasions cover the material, giving it a rough, realistic look even though the material is a [[metal]]. [[Specular highlight]]s are high and realistically modeled at the appropriate edge of the tread using a [[normal mapping|normal map]].]]

[[File:Physically Based Rendering Sample 1.png|thumb|right|An image of [[bricks]] rendered using PBR. Even though this is a rough, [[Opacity (optics)|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 (computer graphics)|Tessellation]] is used to generate an object [[mesh]] from a [[heightmap]] and [[normal mapping|normal map]], creating greater detail.]]

'''Physically based rendering''' ('''PBR''') is a [[computer graphics]] approach that seeks to [[3D rendering|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 [[approximation]]s 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 [[Shader]]s or offline applications using [[Ray tracing (graphics)]] or [[Path tracing]].

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==Process==

[[File:Physically Based Rendering Sample 1.png|thumb|rightupright=1.2|An image of [[bricksBricks]] rendered using PBR. Even though this is a rough, [[Opacity (optics)|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 (computer graphics)|Tessellation]] is used to generate an object [[mesh]] from a [[heightmap]] and [[normal mapping|normal map]], creating greater detail.]]

PBR is, as Joe Wilson puts it, "more of a concept than a strict set of rules"<ref>Wilson, Joe. [https://www.marmoset.co/posts/physically-based-rendering-and-you-can-too/ "Physically Based Rendering – And You Can Too!"] Retrieved on 12 Jan 2017.</ref> – but the concept contains several distinctive points of note. One of these is that – unlike many previous models that sought to differentiate surfaces between non-reflective and reflective – PBR recognizes that, in the real world, as John Hable puts it, "everything is shiny".<ref>Hable, John . [http://filmicgames.com/archives/547 "Everything Is Shiny"] {{Webarchive|url=https://web.archive.org/web/20161205184849/http://filmicgames.com/archives/547 |date=2016-12-05 }}. Retrieved on 14 November 2016.</ref> Even "flat" or "matte" surfaces in the real world such as [[concrete]] will reflect a small degree of light, and many [[metal]]s and [[liquid]]s will reflect a great deal of it. Another thing that PBR models attempt to do is to integrate [[photogrammetry]] - measurements from photographs of real-world materials - to study and replicate real physical ranges of values to accurately simulate [[albedo]], [[gloss (optics)|gloss]], [[reflectivity]], and other physical properties. Finally, PBR puts a great deal of emphasis on [[Specular highlight#Microfacets|microfacets]], and will often contain additional textures and mathematical models intended to model small-scale [[specular highlights]] and [[ambient occlusion|cavities]] resulting from smoothness or roughness in addition to traditional specular or reflectivity maps.