Deferred - Adding deferred rendering to KSP

You'll find an explanation of what the mod does here.

Dependencies

Shabby is needed (currently bundled on the github release but will be separate in future releases and CKAN).

Install instructions

Go to releases and grab the latest .zip. Unzip it, merge the provided GameData folder with your game's GameData folder (typically C:\Program Files\Steam\SteamApps\common\Kerbal Space Program\GameData).

You should see the following folder structure:

Kerbal Space program
└──────GameData
        ├──────000_Harmony
        ├──────Shabby
        └──────zzz_Deferred

Make sure you downloaded the release linked above and not the code, if you see Deferred-Master you messed up and downloaded the code.

Check the mod compatibility list below and update mods as needed.

Reporting issues

To report an issue add screenshots of the issue, reproduction steps and your KSP.log file, otherwise your report may not be taken into account.

Limitations/known issues

Terrain shaders

Only "Ultra" quality terrain shaders are compatible, that includes both atlas and non-atlas terrain shaders. Terrain quality is forced to Ultra when the mod loads.

Names of compatible terrain shaders:

• PQSTriplanarZoomRotation.shader
• PQSTriplanarZoomRotationTextureArray - 1Blend.shader
• PQSTriplanarZoomRotationTextureArray - 2Blend.shader
• PQSTriplanarZoomRotationTextureArray - 3Blend.shader
• PQSTriplanarZoomRotationTextureArray - 4Blend.shader

Transparency

Traditional transparency doesn't work in deferred rendering for opaque objects (only used in the editors in KSP). To emulate transparency, a stylized dissolve effect (left on the below image) is used on fairing-only shaders.

A dithering effect (right on the below image) can be applied on regular shaders but is disabled by default because it is distracting (you'll find an option in the settings file).

Mod compatibility status

In no particular order. Mods that say "renders in forward" means they may appear to render correctly but get no deferred benefits for now (no lighting perf improvements, not compatible with any deferred ambient/lighting/effects)

Debug menu

Using alt + d ( right shift + d on linux) will bring up a simple debug menu cycling between the contents of the g-buffer (albedo, normals, smoothness, specularColor, occlusion) and a composite of the emission+calculated ambient

Transparencies and incompatible forward shaders will render on top of the debug visualization, ignoring the g-buffer mode selected. This can also be used to identify incompatible/forward shaders (ignoring transparencies)

Stencil buffer usage

Only 3 bits of the stencil buffer appear to be available in deferred rendering because the rest are used internally by Unity. This is undocumented for version 2019.4 of Unity but the available bits appear to be bits 0, 1, and 5, which correspond to values 1, 2, and 32. Because this is undocumented this usage could turn out to be wrong and bugs may be discovered in the future. Later versions of the documentation say that only bit 5 is actually available, this may not be true for 2019.4 and seems to work in KSP.

Stencil buffer is useful for applying post effects selectively to certain surfaces, we can take advantage of it here since we are using new shaders and can implement stencil everywhere. I propose the following stencil values be used for masking, they are already used by this mod for replaced shaders:

Writing stencil values

To write stencil values from a shader, add a stencil block with the stencil value to write, e.g for parts:

    Tags { "RenderType"="Opaque" }

    Stencil
    {
        Ref 1
        Comp Always
        Pass Replace
    }  

    CGPROGRAM
    ...

Testing stencil values

For testing/checking stencil values in a post effect, multiple approaches can be used as seen in https://docs.unity3d.com/Manual/SL-Stencil.html

Here are examples to check for the surfaces above or combinations of them

Checking for parts only

Check only for value 1

        Stencil
        {
            Ref 1
            Comp Equal
            ReadMask 35
            Pass Keep
        }

Checking for PQS only

Check only for value 2

        Stencil
        {
            Ref 2
            Comp Equal
            ReadMask 35
            Pass Keep
        }

Checking for Scenery only

Check only for value 3

        Stencil
        {
            Ref 3
            Comp Equal
            ReadMask 35
            Pass Keep
        }

Checking for Parallax grass only

Check only for value 32

        Stencil
        {
            Ref 32
            Comp Equal
            ReadMask 35
            Pass Keep
        }

Checking for PQS or scenery but not grass

Check for values less or equal to 3 greater than 1

        Stencil
        {
            Ref 1
            Comp Less
            ReadMask 3
            Pass Keep
        }

Checking for PQS or scenery or grass

Check for values less or equal to 35 greater than 1

        Stencil
        {
            Ref 1
            Comp Less
            ReadMask 35
            Pass Keep
        }

Checking for grass or scenery but not PQS

Check for values less or equal to 35 greater than 2

        Stencil
        {
            Ref 2
            Comp Less
            ReadMask 35
            Pass Keep
        }