Deferred shading

Advantages

The primary advantage of deferred shading is the decoupling of scene geometry from lighting. Only one geometry pass is required, and each light is only computed for those pixels that it actually affects. This gives the ability to render many lights in a scene without a significant performance hit. There are some other advantages claimed for the approach. These include simpler management of complex lighting resources, ease of managing other complex shader resources, and the simplification of the software rendering pipeline.

Disadvantages

One key disadvantage of deferred rendering is the inability to handle transparency within the algorithm, although this problem is a generic one in Z-buffered scenes and it tends to be handled by delaying and sorting the rendering of transparent portions of the scene. Depth peeling can be used to achieve order-independent transparency in deferred rendering, but at the cost of additional batches and g-buffer size. Modern hardware, supporting DirectX 10 and later, is often capable of performing batches fast enough to maintain interactive frame rates. When order-independent transparency is desired (commonly for consumer applications) deferred shading is no less effective than forward shading using the same technique.

Another serious disadvantage is the difficulty with using multiple materials. It's possible to use many different materials, but it requires more data to be stored in the G-buffer, which is already quite large and takes up a large amount of the memory bandwidth.

One more disadvantage is that, due to separating the lighting stage from the geometric stage, hardware anti-aliasing does not produce correct results anymore since interpolated subsamples would result in nonsensical position, normal, and tangent attributes. One of the usual techniques to overcome this limitation is using edge detection on the final image and then applying blur over the edges, however recently more advanced post-process edge-smoothing techniques have been developed, such as MLAA{{cite web

Deferred lighting

Deferred lighting (also known as Light Pre-Pass) is a modification of the Deferred Shading. This technique uses three passes, instead of two in deferred shading. On first pass over the scene geometry, only normals and specular spread factor are written to the color buffer. The screen-space, “deferred” pass then accumulates diffuse and specular lighting data separately, so a last pass must be made over the scene geometry to output final image with per-pixel shading. The apparent advantage of deferred lighting is a dramatic reduction in the size of the G-Buffer. The obvious cost is the need to render the scene geometry twice instead of once. An additional cost is that the deferred pass in deferred lighting must output diffuse and specular irradiance separately, whereas the deferred pass in deferred shading need only output a single combined radiance value.

Due to reduction of the size of the G-buffer this technique can partially overcome one serious disadvantage of the deferred shading - multiple materials. Another problem that can be solved is MSAA. Deferred lighting can be used with MSAA on DirectX 9 hardware.

Deferred lighting in commercial games

Use of the technique has increased in video games because of the control it enables in terms of using a large amount of dynamic lights and reducing the complexity of required shader instructions. Some examples of games using deferred lighting are:

• Alan Wake
• Assassin's Creed III
• BioShock Infinite
• Black Mesa
• Blur
• Brink
• Crackdown and Crackdown 2
• Crysis 2
• Dead Space,{{cite web
• Deus Ex: Human Revolution
• Dragon's Dogma
• Guild Wars 2
• Halo: Reach
• inFamous and inFamous 2
• LittleBigPlanet
• Metal Gear Solid V: Ground Zeroes
• Metal Gear Solid V: The Phantom Pain
• Minecraft
• Red Dead Redemption
• Resistance series
• Rochard
• Shift 2: Unleashed
• StarCraft II {{cite web
• Uncharted and Uncharted 2
• Vanquish
• Ghost of Tsushima

Deferred shading in commercial games

In comparison to deferred lighting, this technique is not very popular due to high memory size and bandwidth requirements, especially on seventh generation consoles where graphic memory size and bandwidth are limited and often bottlenecks.

• Amnesia: The Dark Descent
• Battlefield 3
• Dota 2
• Dungeons
• Digital Combat Simulator (DCS) World 2.5
• Grand Theft Auto IV
• Killzone 2 and Killzone 3
• Mafia II
• Miner Wars 2081
• Metro 2033
• Rift
• Shrek
• Splinter Cell: Conviction
• The S.T.A.L.K.E.R. game series: Shadow of Chernobyl, Clear Sky and Call of Pripyat{{cite web
• Tabula Rasa{{cite web | archive-url = https://web.archive.org/web/20090203081102/http://http.developer.nvidia.com/GPUGems3/gpugems3_ch19.html | archive-date = 2009-02-03 | url-status = dead
• Trine
• Trine 2
• Viva Pinata

Game engines featuring deferred shading or rendering techniques

• AnvilNext
• Chrome Engine
• CryEngine 3
• Fox Engine
• Frostbite 2{{cite web |archive-url=https://web.archive.org/web/20110825085117/http://publications.dice.se/attachments/GDC11_LightingYouUpInBattlefield3.pptx |url-status=dead |archive-date=August 25, 2011
• GameStart{{cite web |url-status = dead
• Haemimont Games Engine (HGE)
• I-Novae{{cite web | archive-url = https://archive.today/20130126165723/http://www.infinity-universe.com/Infinity/index.php?option=com_content&task=view&id=105&Itemid=26 | url-status = dead | archive-date = 2013-01-26
• Leadwerks
• MT Framework
• Rockstar Advanced Game Engine{{cite web
• Torque 3D{{cite web
• Unity{{cite web
• Unreal Engine 4{{cite web
• Vision{{cite web |url-status = dead
• Creation Engine as of Fallout 4 and Skyrim SE{{cite web
• Fusion Engine (early Illusion Engine) as of Mafia III and Mafia: Definitive Edition
• Raylib{{cite web
• X-Ray Engine

History

The idea of deferred shading was originally introduced by Michael Deering and his colleagues in a paper{{cite journal |url-status = dead

References

References

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