High-dynamic-range rendering: Difference between revisions

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{{distinguish|High dynamic range video}}

{{Short description|Rendering of computer graphics scenes by using lighting calculations done in high-dynamic-range}}

[[File:Lost Coast HDR comparison.png|thumb|300px|right|A comparison of the standard fixed-aperture rendering (left) with the HDR rendering (right) in the video game ''[[Half-Life 2: Lost Coast]].'' The HDRR was tone mapped to SDR for broad compatibility with almost all displays.]]

'''High-dynamic-range rendering''' ('''HDRR''' or '''HDR rendering'''), also known as '''high-dynamic-range lighting''', is the [[Rendering (computer graphics)|rendering]] of [[computer graphics]] scenes by using [[computer graphics lighting|lighting]] calculations done in [[high dynamic range]] (HDR). This allows preservation of details that may be lost due to limiting [[contrast ratio]]s. [[Video game]]s and [[Computer animation|computer-generated movies and special effects]] benefit from this as it creates more realistic scenes than with more simplistic lighting models.

'''High-dynamic-range rendering''' ('''HDRR''' or '''HDR rendering'''), also known as '''high-dynamic-range lighting''', is the [[Rendering (computer graphics)|rendering]] of [[computer graphics]] scenes by using [[computer graphics lighting|lighting]] calculations done in [[high dynamic range]] (HDR). This allows preservation of details that may be lost due to limiting [[contrast ratio]]s. [[Video game]]s and [[Computer animation|computer-generated movies and special effects]] benefit from this as it creates more realistic scenes than with more simplistic lighting models. HDRR was originally required to [[Tone mapping|tone map]] the rendered image onto [[Standard-dynamic-range video|Standard Dynamic Range]] (SDR) displays, as the first [[High-dynamic-range television#Displays|HDR capable displays]] did not arrive until the 2010s. However if a modern HDR display is available, it is possible to instead display the HDRR with even greater contrast and realism.

Graphics processor company [[Nvidia]] summarizes the motivation for HDR in three points: bright things can be really bright, dark things can be really dark, and details can be seen in both.<ref name="6800_Leagues_HDR">{{cite web | url= http://download.nvidia.com/developer/presentations/2004/6800_Leagues/6800_Leagues_HDR.pdf | title= High Dynamic Range Rendering (on the GeForce 6800) | author= Simon Green and Cem Cebenoyan | year= 2004 | publisher= nVidia | work= [[GeForce 6]] Series | page= 3 }}</ref>

Graphics processor company [[Nvidia]] summarizes the motivation for HDRHDRR in three points: bright things can be really bright, dark things can be really dark, and details can be seen in both.<ref name="6800_Leagues_HDR">{{cite web | url= http://download.nvidia.com/developer/presentations/2004/6800_Leagues/6800_Leagues_HDR.pdf | title= High Dynamic Range Rendering (on the GeForce 6800) | author= Simon Green and Cem Cebenoyan | year= 2004 | publisher= nVidia | work= [[GeForce 6]] Series | page= 3 }}</ref>

==History==

The use of [[high-dynamic-range imaging]] (HDRI) in computer graphics was introduced by Greg Ward in 1985 with his open-source [[Radiance (software)|Radiance]] rendering and ''lighting simulation'' software which created the first file format to retain a high-dynamic-range image. HDRI languished for more than a decade, held back by limited computing power, storage, and capture methods. Not until recently{{When|date=January 2025|reason=“Recently” is ambiguous, especially when referring to a 40-year-old technology. Also, it wasn’t all that recent: if a Half-Life 2 expansion could use HDR in 2005 or so, that’s halfway between the invention of the technology and the current year. That is by no means recent in the history of HDR.}} has the technology to put HDRI into practical use been developed.<ref name=reinhard1>{{cite book

| last = Reinhard

| first = Erik

Line 22 ⟶ 24:

|access-date=18 August 2009}}</ref>

In 1990, Eihachiro Nakame, ''etand al.'',associates presented a lighting model for driving simulators that highlighted the need for high-dynamic-range processing in realistic simulations.<ref name="nakamae1">{{cite book

| author = Eihachiro Nakamae

|author2=Kazufumi Kaneda |author3=Takashi Okamoto |author4=Tomoyuki Nishita

|s2cid=11880939 | title= A lighting model aiming at drive simulators

| journal=Siggraph

| year=1990

| doi = 10.1145/97879.97922

| pageisbn = 395978-0201509335

|s2cid=11880939 |chapter title= A lighting model aiming at drive simulators

| isbn = 978-0201509335 }}</ref>

| title = Proceedings of the 17th annual conference on Computer graphics and interactive techniques

| year = 1990

| last1 = Nakamae

| authorfirst1 = Eihachiro Nakamae

| last2 = Kaneda

| first2 = Kazufumi

| last3 = Okamoto

| first3 = Takashi

| last4 = Nishita

| first4 = Tomoyuki

| pages = 395–404

| s2cid = 1764391011880939

}}</ref>

In 1995, Greg Spencer presented ''Physically-based glare effects for digital images'' at [[SIGGRAPH]], providing a quantitative model for flare and blooming in the human eye.<ref name="spencer1">{{cite book |author = Greg Spencer

|author2 = Peter Shirley

|author3 = Kurt Zimmerman

|author4 = Donald P. Greenberg

|s2cid = 17643910

|title = Physically-based glare effects for digital images

|journal = Siggraph

|year = 1995

|doi = 10.1145/218380.218466

|page = [https://archive.org/details/computergraphics00sigg/page/325 325]

|isbn = 978-0897917018

|citeseerx = 10.1.1.41.1625

|title chapter = Physically-based glare effects for digital images

|url = https://archive.org/details/computergraphics00sigg/page/325

|title = Proceedings of the 22nd annual conference on Computer graphics and interactive techniques - SIGGRAPH '95

}}</ref>

|year = 1995

|last1 = Spencer

|first1 = Greg

|author2 last2 = Peter Shirley

|first2 = Peter

|author3 last3 = Kurt Zimmerman

|first3 = Kurt

|author4 last4 = Donald P. Greenberg

|first4 = Donald P.

|s2cid = 17643910

}}</ref>

In 1997, [[Paul Debevec]] presented ''Recovering high dynamic range radiance maps from photographs''<ref>{{cite journalbook

| doi=10.1145/258734.258884

| author=[[Paul E. Debevec]] and [[Jitendra Malik]]

| doi-access=free

| title= Recovering high dynamic range radiance maps from photographs

| author=[[Paul E. Debevec]] and [[Jitendra Malik]] | title=Proceedings of the 24th annual conference on Computer graphics and interactive techniques - SIGGRAPH '97

| journal=Siggraph

| titlechapter= Recovering high dynamic range radiance maps from photographs

| yeardate=1997

| url=http://www.debevec.org/Research/HDR

| pages=369–378

}}</ref> at SIGGRAPH, and the following year presented ''Rendering synthetic objects into real scenes''.<ref>{{cite journal

| isbn=0897918967

}}</ref> at SIGGRAPH, and the following year presented ''Rendering synthetic objects into real scenes''.<ref>{{cite journalbook

| author=Paul E. Debevec

| title=Proceedings of the 25th annual conference on Computer graphics and interactive techniques - SIGGRAPH '98

| titlechapter= Rendering synthetic objects into real scenes: bridgingBridging traditional and image-based graphics with global illumination and high dynamic range photography

| yeardate=1998

| pages=189–198

| author-link=Paul E. Debevec

| doi=10.1145/280814.280864

| title= Rendering synthetic objects into real scenes: bridging traditional and image-based graphics with global illumination and high dynamic range photography

| isbn=0897919998

| journal=Siggraph

| url doi-access= http://www.debevec.org/Research/IBL/ free}}</ref> These two papers laid the framework for creating HDR ''light probes'' of a ___location, and then using this probe to light a rendered scene.

| year=1998

| url = http://www.debevec.org/Research/IBL/ }}</ref> These two papers laid the framework for creating HDR ''light probes'' of a ___location, and then using this probe to light a rendered scene.

HDRI and HDRL (high-dynamic-range [[image-based lighting]]) have, ever since, been used in many situations in 3D scenes in which inserting a 3D object into a real environment requires the light probe data to provide realistic lighting solutions.

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In gaming applications, ''[[Riven|Riven: The Sequel to Myst]]'' in 1997 used an HDRI postprocessing shader directly based on Spencer's paper.<ref name="computergraphicsworld">{{cite journal|author=Forcade, Tim|date=February 1998|title=Unraveling Riven|journal=Computer Graphics World}}</ref> After [[Electronic Entertainment Expo|E3]] 2003, [[Valve Corporation|Valve]] released a demo movie of their [[Source engine]] rendering a cityscape in a high dynamic range.<ref>

{{cite web | url= https://www.youtube.com/watch?v=Xb1yrhgRVMQ |archive-url=https://ghostarchive.org/varchive/youtube/20211221/Xb1yrhgRVMQ |archive-date=2021-12-21 |url-status=live| title= Half-Life 2: Source DirectX 9.0 Effects Trailer (2003) | author= Valve | year= 2003 | publisher= YouTube }}{{cbignore}}

</ref> The term was not commonly used again until E3 2004, where it gained much more attention when [[Epic Games]] showcased [[Unreal Engine technology#Unreal Engine 3|Unreal Engine 3]] and Valve announced ''[[Half-Life 2: Lost Coast]]'' in 2005, coupled with open-source engines such as [[OGRE 3D]] and open-source games like ''[[Nexuiz]]''.

By the 2010s, [[High-dynamic-range television#Displays|HDR displays]] first became available. With higher contrast ratios, it is possible for HDRR to reduce or eliminate [[tone mapping]], resulting in an even more realistic image.

==Examples==

One of the primary advantages of HDR rendering is that details in a scene with a large contrast ratio are preserved. Without HDRHDRR, areas that are too dark are clipped to black and areas that are too bright are clipped to white. These are represented by the hardware as a floating point value of 0.0 and 1.0 for pure black and pure white, respectively.

Another aspect of HDR rendering is the addition of perceptual cues which increase apparent brightness. HDR rendering also affects how light is preserved in optical phenomena such as [[Reflection (physics)|reflections]] and [[refraction]]s, as well as transparent materials such as glass. In LDR rendering, very bright light sources in a scene (such as the sun) are capped at 1.0. When this light is reflected the result must then be less than or equal to 1.0. However, in HDR rendering, very bright light sources can exceed the 1.0 brightness to simulate their actual values. This allows reflections off surfaces to maintain realistic brightness for bright light sources.

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===Output to displays===

Although many manufacturers claim very high numbers, [[plasma displays]], [[LCDliquid-crystal displaysdisplay]]s, and [[Cathode ray tube|CRT displaysdisplay]]s can deliver only a fraction of the contrast ratio found in the real world, and these are usually measured under ideal conditions.{{Citation needed|date=February 2015}} The simultaneous contrast of real content under normal viewing conditions is significantly lower.

Some increase in dynamic range in [[LCD monitors]] can be achieved by automatically reducing the backlight for dark scenes. For example, LG calls this technology "Digital Fine Contrast";<ref>[http://www.lge.com/about/press_release/detail/PRO%7CNEWS%5EPRE%7CMENU_20075_PRE%7CMENU.jhtml Digital Fine Contrast]</ref> Samsung describes it as "dynamic contrast ratio". Another technique is to have an array of brighter and darker LED backlights, for example with systems developed by BrightSide Technologies.<ref>[http://www.dolby.com/promo/hdr/technology.html BrightSide Technologies is now part of Dolby -] {{webarchive|url=https://web.archive.org/web/20070910145331/http://www.dolby.com/promo/hdr/technology.html |date=2007-09-10 }}</ref>

[[OLED]] displays have better dynamic range capabilities than LCDs, similar to plasma but with lower power consumption. [[Rec. 709]] defines the color space for [[HDTV]], and [[Rec. 2020]] defines a larger but still incomplete color space for [[ultra-high-definition television]].

Since the 2010s, OLED and other [[High-dynamic-range television#Displays|HDR display technologies]] have reduced or eliminated the need for [[tone mapping]] HDRR to [[Standard-dynamic-range video|standard dynamic range]].

===Light bloom===

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Flare is the diffraction of light in the human lens, resulting in "rays" of light emanating from small light sources, and can also result in some chromatic effects. It is most visible on point light sources because of their small visual angle.<ref name="spencer1"/>

OtherwiseTypical display devices cannot display light as bright as the Sun,{{Non sequitur|date=Septemberand ambient room lighting prevents them from displaying true 2021|reason=Otherwiseblack. to what?}}Thus HDR rendering systems have to map the full dynamic range of what the eye would see in the rendered situation onto the capabilities of the device. This [[tone mapping]] is done relative to what the virtual scene camera sees, combined with several [[full screen effect]]s, e.g. to simulate dust in the air which is lit by direct sunlight in a dark cavern, or the scattering in the eye.

[[Tone mapping]] and [[Bloom (shader effect)|blooming shaders]] can be used together to help simulate these effects.

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{{main|Tone mapping}}

Tone mapping, in the context of graphics rendering, is a technique used to map colors from high dynamic range (in which lighting calculations are performed) to a lower dynamic range that matches the capabilities of the desired display device. Typically, the mapping is non-linear – it preserves enough range for dark colors and gradually limits the dynamic range for bright colors. This technique often produces visually appealing images with good overall detail and contrast. Various tone mapping operators exist, ranging from simple real-time methods used in computer games to more sophisticated techniques that attempt to imitate the perceptual response of the human visual system.

[[High-dynamic-range television|HDR displays]] with higher dynamic range capabilities can reduce or eliminate the tone mapping required after HDRR, resulting in an even more realistic image.

==Applications in computer entertainment==

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===Development of HDRR through DirectX===

Complex shader effects began their days with the release of [[Shader|Shader Model 1.0]] with [[DirectX]] 8. Shader Model 1.0 illuminated 3D worlds with what is called standard lighting. Standard lighting, however, had two problems:

#Lighting precision was confined to 8 bit integers, which limited the contrast ratio to 256:1. Using the [[HSV color space|HVS color model]], the value (V), or brightness of a color has a range of 0 – 255. This means the brightest white (a value of 255) is only 255 levels brighter than the darkest shade above pure black (i.e.: value of 0).

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===Game engines that support HDR rendering===

*[[Unreal Engine| 5]]
*[[Unreal Engine 54]]

*[[Unreal Engine|Unreal Engine 3]]<ref>{{cite web|url=http://www.unrealengine.com/features/rendering/ |title=Rendering – Features – Unreal Technology |year=2006 |work=Epic Games |access-date=2011-03-15 |url-status=dead |archive-url=https://web.archive.org/web/20110307074455/http://www.unrealengine.com/features/rendering |archive-date=2011-03-07 }}</ref>

*[[Unreal Engine|Unreal Engine 4]]

*[[Unreal Engine|Unreal Engine 3]]<ref>{{cite web|url=http://www.unrealengine.com/features/rendering/ |title=Rendering – Features – Unreal Technology |year=2006 |work=Epic Games |access-date=2011-03-15 |url-status=dead |archive-url=https://web.archive.org/web/20110307074455/http://www.unrealengine.com/features/rendering |archive-date=2011-03-07 }}</ref>

*[[Chrome Engine|Chrome Engine 3]]

*[[Source (game engine)|Source]]<ref>{{cite web | url=http://source.valvesoftware.com/rendering.php | title=SOURCE – RENDERING SYSTEM | year=2007 | work=Valve | access-date=2011-03-15 | url-status=dead | archive-url=https://web.archive.org/web/20110323182005/http://source.valvesoftware.com/rendering.php | archive-date=2011-03-23 }}</ref>

*[[Source 2 (game engine)|Source 2]]

*[[Serious Engine 2]]

*[[MT Framework|MT Framework 2]]

*[[RE Engine]]

*[[REDengine|REDengine 3]]<ref>{{cite web | url=http://www.pcgamer.com/the-amazing-technology-of-the-witcher-3/ | title=The Amazing Technology of The Witcher 3 | year= 2015 | work= PC-Gamer | access-date= 2016-05-08}}</ref>

*[[CryEngine]],<ref>{{cite web | url=http://www.xbitlabs.com/articles/video/display/farcry13.html | title=FarCry 1.3: Crytek's Last Play Brings HDR and 3Dc for the First Time | year=2004 | work=X-bit Labs | access-date=2011-03-15 | url-status=dead | archive-url=https://web.archive.org/web/20080724214109/http://www.xbitlabs.com/articles/video/display/farcry13.html | archive-date=2008-07-24 }}</ref> [[CryEngine 2]],<ref>{{cite web | url=http://crytek.com/cryengine/cryengine2/overview | title=CryEngine 2 – Overview | year= 2011| work=CryTek | access-date= 2011-03-15 }}</ref> [[CryEngine 3]]

*[[Dunia Engine]]

*[[Gamebryo]]

*[[Godot (game engine)]]{{cn|date=May 2025}}

*[[Decima (game engine)|Decima]]<ref>{{Cite news|last=Pereira|first=Chris|date=December 3, 2016|title=Kojima Partnering With Killzone, Horizon Dev Guerrilla for Death Stranding|work=[[GameSpot]]|publisher=[[CBS Interactive]]|url=https://www.gamespot.com/articles/kojima-partnering-with-killzone-horizon-dev-guerri/1100-6445954/|url-status=live|access-date=December 3, 2016|archive-url=https://web.archive.org/web/20191204214057/https://www.gamespot.com/articles/kojima-partnering-with-killzone-horizon-dev-guerri/1100-6445954/|archive-date=December 4, 2019}}</ref>

*[[Unity (game engine)|Unity]]

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*[[Unigine]]<ref>{{cite web | url=http://unigine.com/products/unigine/ | title=Unigine Engine – Unigine (advanced 3D engine for multi-platform games and virtual reality systems) | year=2011 | work=Unigine Corp. | access-date=2011-03-15 }}</ref>

*[[Frostbite 2]]

* [[Bohemia Interactive|Real Virtuality 2, 3, and 4]]{{cn|date=April 2024}}

*[[Real Virtuality (game engine)#Real Virtuality 2|Real Virtuality 2]], [[Real Virtuality (game engine)#Real Virtuality 3|Real Virtuality 3]], [[Real Virtuality (game engine)#Real Virtuality 4|Real Virtuality 4]]

* [[HPL Engine 3]]

* Babylon JS <ref>{{cite web |url=http://doc.babylonjs.com/page.php?p=25362 |title=BabylonDoc |access-date=2015-07-03 |url-status=dead |archive-url=https://web.archive.org/web/20150704155945/http://doc.babylonjs.com/page.php?p=25362 |archive-date=2015-07-04 }}</ref>

* [[Torque 3D]]<ref>{{Cite web | url=https://github.com/GarageGames/Torque3D/blob/development/Templates/Full/game/core/scripts/client/postFx/hdr.cs |title = MIT Licensed Open Source version of Torque 3D from GarageGames: GarageGames/Torque3D| website=[[GitHub]] |date = 2019-08-22}}</ref>

* [[X-Ray Engine]]

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*[https://web.archive.org/web/20110711112223/http://transporter-game.googlecode.com/files/HDRRenderingInOpenGL.pdf High Dynamic Range Rendering in OpenGL] ([[PDF]])

*[http://www.microsoft.com/whdc/winhec/partners/shadermodel30_NVIDIA.mspx Microsoft's technical brief on SM3.0 in comparison with SM2.0]

*[https://web.archive.org/web/20060113032428/http://www.tomshardware.com/2006/01/13/new_3d_graphics_card_features_in_2006/ Tom's Hardware: New Graphics Card Features of 2006]

*[https://web.archive.org/web/20060421205054/http://users.erols.com/chare/video.htm List of GPU's compiled by Chris Hare]

*[http://www.techpowerup.com/gpudb/ techPowerUp! GPU Database]

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*[http://www.uvlist.net/groups/info/hdrlighting List of video games supporting HDR]

*[https://web.archive.org/web/20100918023123/http://hdr-photography.org/ Examples of high dynamic range photography]

*[https://hdri-haven.com/ HDRIHaven - Creative Commons HDRI Maps Library]

{{Graphics Processing Unit}}