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{{LanguageBar|title=Deferred renderer (shading & lighting)}}
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'''[[WP:Deferred shading|Deferred shading]]''' is a screen-space shading technique that is performed on a second rendering pass, after the vertex and pixel shaders are rendered.

'''[[WP:Deferred shading#Deferred lighting|Deferred lighting]]''' (also known as Light Pre-Pass) is an modification of Deferred shading, which uses three passes, instead of two in deferred shading, where only the lighting calculations are deferred. The shading is still done in the initial pass, but the lighting component of the shading is calculated later.

Both deferred rendering techniques allows many lights to be rendered on the scene without a significant performance hit, however deferred lighting is slightly more demanding than deferred shading, but deferred lighting uses less memory than deferred shading, and rendering transparency & [[Anti-aliasing#MSAA|MSAA]] support is easier on deferred lighting.

Nonetheless, it is much different from the default (usually static) [[radiosity]] lighting that comes with {{Src|4}} (primarily using '''Forward renderer'''). 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. However, there are also other rendering methods such as "Forward+/Tile" or [[Clustered rendering|Clustered Forward]] which can make dynamic lights less demanding on forward renderer (currently {{p2ce|2}} is the only upcoming Source game, along with {{obm|2}} utilizing this technique).

==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 and deferred shading, like in {{apex|2}} and {{bms|2}} (the latter title 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, and even more demanding on deferred shading compared to forward rendering, and MSAA is harder to implement on deferred shading, while it was easier to implement on deferred lighting.
*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]]

==Usage==
=== Source ===
Few {{src|1|nt=1}} games utilize this technique, as it's complicated to implement, the games that do use this are:
==== Deferred shading ====
*{{Tfbranch|4}} (including {{apex|4}})
==== Deferred lighting ====
*{{asd|4}} 
*{{bms|4}}
*{{lw|4}}
*{{p2d|4}}
*{{hammer|4}} (Lighting Preview in stock HL2 and {{strata|4}})
**{{Confirm|Hammer use Deferred lighting or shading?}}
=== Source 2 ===
==== Deferred shading ====
* {{Dota2|4}}{{Cite|2}} (formerly {{src|1}} which also use deferred shading)
* {{Deadlock|4}}
* {{Hammer5|nt=0|4}}{{confirm}}

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

== See also ==
* {{asd|1}}
* [[Clustered rendering]] - similar technique, can be implemented on both forward and deferred renderer.
* [[Light editor]]
* [[Volumetric lighting]]
* {{w|Deferred lighting}} (Wikipedia)
=== Entities ===
* {{ent|newLight_Point}}
* {{ent|newLight_Spot}}
* {{ent|light_deferred}}
* {{ent|light_deferred_global}}

==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. }}
{{Ref2|cite id=2|Several commands related to deferred rendering such as {{code|r_deferred_}} can be seen in {{dota2|1}}. Additionally, enabling MSAA via console commands in the original (Source 1) release of Dota 2 will breaks the renderer. Since [https://developer.valvesoftware.com/w/index.php?title{{=}}Dota_2&oldid{{=}}167294 April 27, 2012], it is confirmed that Dota 2 uses deferred shading, and use FXAA (referred as Screen-space Anti-aliasing when the [[Dota 2]] page on VDC was edited in 2012).}}
}}

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