View source for Hedgehog Engine 2 - Deferred Rendering

Deferred rendering is a rendering technique used in Hedgehog Engine 2 games.

The “standard” way of rendering is called “forward rendering”, and simply draws one mesh after another, including all the lighting calculations. But since one mesh can hide a significant portion of another, many of those lighting calculations go to waste and could be better spent elsewhere.

This is where deferred rendering comes in: Instead of calculating the lighting for every mesh individually, a meshes rendering properties can be stored in multiple frame buffers, which can then be composited together and achieve a similar result!

=== An Example ===
Here are some example frame buffers for a scene that uses deferred rendering, captured in Kingdom Valley from Shadow Generations:

{| class="wikitable"
|-
|style="text-align:center;"|[[File:SXSG Deferred Rendering Albedo.png|center|The albedo buffer of Kingdom Valley in Shadow Generations]] 
The albedo buffer
|style="text-align:center;"|[[File:SXSG Deferred Rendering Normals.png|center|The normal buffer of Kingdom Valley in Shadow Generations]]
The specular, inverted smoothness and ambient occlusion buffer
|-
|style="text-align:center;"|[[File:SXSG Deferred Rendering PBR.png|center|The specular, roughness and ambient occlusion buffer of Kingdom Valley in Shadow Generations]]
The normals buffer
|style="text-align:center;"|[[File:SXSG Deferred Rendering Emission.png|center|The emission buffer of Kingdom Valley in Shadow Generations]]
The Emission buffer
|}

== Drawbacks ==
While faster than forward rendering, this technique is not perfect and has several drawbacks:
* Requires more GPU memory to store the frame buffers
* Does not allow for transparency blending
* No multi-sample-anti-aliasing (MSAA)

Since transparency is a very important feature, only opaque and punch-through meshes use deferred rendering, while transparent meshes get drawn after the deferred buffers have been combined.