View source for Deferred lighting

{{LanguageBar|title=Deferred lighting and Deferred shading}}
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'''Deferred lighting''' is an alternate lighting technique and modification of '''[[WP:Deferred shading|deferred shading]]''', a screen-space shading technique that allows many lights to be rendered on the scene without a significant performance hit.

It is much different from the default (usually static) [[radiosity]] lighting that comes with {{Src|4}}. It uses many different lighting passes to generate higher quality lighting, with real-time shadows.

{{Src2|4}} games generally use forward rendering, like {{hlalyx|4}}, but games like {{d2|4}} and {{deadlock|4}} use deferred rendering.
==Differences from vanilla radiosity==
When compiling a map in any of {{Valve|4|addtext='s}} games, each map is run through [[VRAD]] (which can take a long time depending on hardware and [[Lighting_optimization|optimizations]]), which takes data from all the light sources and compiles them into a '''lightmap''' texture. While this does provide high-quality and variable lighting, it is completely static, save for the limited ability to toggle on some lights in a scene. The difference between [[radiosity]] and deferred lighting is that deferred lighting computes all its lights in real-time, with a low performance cost ([[cheap]]). The game takes data from the normals of the object, its geometry, its albedo, and its specular lighting to create real-time accurate lighting.

==Dynamic lights in forward rendering==
Performance can be significantly reduced if there are too many dynamic light entities like {{code|[[env_projectedtexture]]}} (also used on [[player]]'s flashlight since {{src07}}) in forward rendering. Other dynamic lights such as {{code|light_dynamic}} also reduce performance if the lightmap has a small luxel scale and/or the light has [[Lightstyle|custom appearance]] (lightstyles). Additionally, {{code|env_projectedtexture}} is also limited by the {{src|1}} engine itself (by default), meaning that it only works properly with one {{code|env_projectedtexture}} entity without engine modifications. Deferred lighting (and deferred shading) does not have these issues or limitations and almost an infinite number of dynamic lights can be active with faster performance than with forward rendering.

==Features==
*Quite cheap real-time lighting and shadows.
*Almost an infinite number of dynamic lights that can be active (stock [[Source]] only allows for one {{ent|env_projectedtexture}} at a time).
*High-fidelity [[godrays]].
*[[Volumetric lighting]].
*Light cookies (premade shadow maps).

==Drawbacks==
*Traditional anti-aliasing methods like [[MSAA]] might not work with deferred lighting, like in {{bms|2}} (which replaced it with FXAA because MSAA caused certain models to have a glowing outline),{{Cite|1}} but it depends how it's implemented in the game, as {{asd|1}}, and {{lw|1}} still support it, though it's recommended that you use post-processing anti-aliasing methods instead as they work best with deferred lighting, and have a smaller performance hit. MSAA is also more demanding with deferred lighting/shading compared to forward rendering.
*All lightmaps are disabled and only deferred lighting lights the world. {{only|{{asd}}}}
*Can be more taxing on older systems.
*DX9 SM3 or later only, older [[DirectX]] compatibility versions are not supported.

==Media==
[[File:Deferred phong ref.png|800px]]

==Availability==
=== Source ===
Few {{src|1|nt=1}} games utilize this lighting technique, as it's complicated to implement, the games that do use this are:
*{{asd|4}} 
*{{bms|4}}
*{{lw|4}}
*{{p2d|4}}
*{{Tfbranch|4}} (including {{apex|4}}) &mdash; using deferred shading
*{{hammer|4}} (Lighting Preview in stock HL2 and {{strata|4}})
=== Source 2 ===
* {{Dota2|4}}
* {{Deadlock|4}}
* {{Hammer5|nt=0|4}}{{confirm}}

==Tutorials==
* [[Implementing Deferred lighting into Source 2013]]

== See also ==
* {{asd|1}}
* [[Light editor]]
* [[Volumetric lighting]]
* {{ent|newLight_Point}}
* {{ent|newLight_Spot}}
* {{ent|light_deferred}}
* {{ent|light_deferred_global}}
* {{w|Deferred lighting}} (Wikipedia)

==External links==
* [https://learnopengl.com/Advanced-Lighting/Deferred-Shading Deferred Shading] on LearnOpenGL (basics)

{{references|1=
{{ref2|cite id=1|access-date=May 10, 2024|[https://store.steampowered.com/news/app/362890/view/4041374038285692283 Xen Technical Beta] and [https://steamcommunity.com/sharedfiles/filedetails/?id{{=}}1960023856 Screenshot by [TC<nowiki>]</nowiki>Ciaиєz ITA]:<br>
'''Known Issues - Haloing Around Props/Object'''<br>
'''MSAA''' is causing outlines around certain objects. MSSA is a performance killer and we hope to have a better solution for anti-aliasing with the Xen release. To remove the haloing/outline, simply turn off MSAA. }}
}}

[[Category:Graphics]]
[[Category:Shaders]]
[[Category:Glossary]]
[[Category:Technical]]