High-dynamic-range rendering: Difference between revisions

Revision as of 15:34, 24 November 2024

Revision as of 03:09, 30 November 2024

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{{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. 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 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==

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{{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 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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[[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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{{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==