Computer graphics lighting: Difference between revisions

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=== Area ===
Area lights are 3D objects which emit light. Whereas point lights and spot lights sources are considered infinitesimally small points, area lights are treated as physical shapes.<ref>{{cite conference |last1=Lagarde |first1=Sebastien |author-link1= |last2=de Rousiers |first2=Charles |author-link2= |date=Summer 2014 |title=Moving Frostbite to Physically Based Rendering 3.0 |url=https://www.ea.com/frostbite/news/moving-frostbite-to-pb |conference=SIGGRAPH |___location= |publisher= |pages= |id= |book-title=}}</ref> Area light produce softer shadows and more realistic lighting than point lights and spot lights.<ref>{{Cite book |lastlast1=Pharr |firstfirst1=Matt |title=Physically Based Rendering: From Theory to Implementation |last2=Humphreys |first2=Greg |last3=Wenzel |first3=Jakob |publisher=Morgan Kaufmann |year=2016 |isbn=978-0128006450 |edition=3rd |language=English}}</ref>
 
=== Ambient ===
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=== Lightwarp ===
A lightwarp is a technique of which an object in the geometrical world [[refracts]] light based on the [[Unit vector|direction]] and [[Intensity (physics)|intensity]] of the light. The light is then [[Wave function|warped]] using an ambient diffuse term with a range of the [[color spectrum]]. The light then may be [[reflectively]] scattered to produce a higher [[depth of field]], and [[refracted]]. The technique is used to produce a [[Style_(visual_arts)#Stylization|unique rendering style]] and can be used to limit [[overexposure]] of objects. Games such as [[Team Fortress 2]] use the rendering technique to create a [[cartoon]] [[cel shaded]] stylized look.<ref>{{Cite webbook|chapter-url=https://hal.inria.fr/inria-00449828|titlechapter=Radiance Scaling for Versatile Surface Enhancement|first1=Romain|last1=Vergne|first2=Romain|last2=Pacanowski|first3=Pascal|last3=Barla|first4=Xavier|last4=Granier|first5=Christophe|last5=Schlick|title=Proceedings of the 2010 ACM SIGGRAPH symposium on Interactive 3D Graphics and Games |date=February 19, 2010|pages=143–150 |publisher=ACM|via=hal.inria.fr|doi=10.1145/1730804.1730827|isbn=9781605589398 |s2cid=18291692 }}</ref>
 
== Lighting interactions ==
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{{Main articles|Ray tracing (graphics)}}
[[File:Ray-traced steel balls.jpg|thumb|Image rendered using ray tracing]]
Light sources emit rays that interact with various surfaces through absorption, reflection, or refraction.<ref name=":72" /> An observer of the scene would see any light source that reaches their eyes; a ray that does not reach the observer goes unnoticed.<ref>{{Cite web|url=https://developer.nvidia.com/rtx/raytracing|title=Introducing the NVIDIA RTX Ray Tracing Platform|date=2018-03-06|website=NVIDIA Developer|language=en|access-date=2019-11-08}}</ref> It is possible to simulate this by having all of the light sources emit rays and then compute how each of them interact with all of the objects in the scene.<ref name=":17">Reif, J. H. (1994). "[https://users.cs.duke.edu/~reif/paper/tygar/raytracing.pdf Computability and Complexity of Ray Tracing]"(PDF). ''Discrete and Computational Geometry''.</ref> However, this process is inefficient as most of the light rays would not reach the observer and would waste processing time.<ref name=":21">Wallace, John R.; Cohen, Michael F.; Greenberg, Donald P. (1987). "A Two-pass Solution to the Rendering Equation: A Synthesis of Ray Tracing and Radiosity Methods". ''Proceedings of the 14th Annual Conference on Computer Graphics and Interactive Techniques''. SIGGRAPH '87. New York, NY, USA: ACM: 311–320. {{doi|10.1145/37401.37438}}. {{ISBN|9780897912273}}.</ref> Ray tracing solves this problem by reversing the process, instead sending view rays from the observer and calculating how they interact until they reach a light source.<ref name=":17" /> Although this way more effectively uses processing time and produces a light simulation closely imitating natural lighting, ray tracing still has high computation costs due to the high amounts of light that reach viewer's eyes.<ref name=":0">{{Cite journal|last=Greenberg|first=Donald P.|date=1989-04-14|title=Light Reflection Models for Computer Graphics|journal=Science|language=en|volume=244|issue=4901|pages=166–173|doi=10.1126/science.244.4901.166|issn=0036-8075|pmid=17835348|bibcode=1989Sci...244..166G |s2cid=46575183 }}</ref>
 
==== Radiosity ====