Post Process Shader format

The effect JSON is defined as an object. Accepted keys are targets and passes, both arrays of the corresponding type. There are no mandatory keys.

Types

Target

Can be in one of two forms:

• a string (assumed to resolve to a "target" key in the object),
• an object.

In the case of an object, the following keys are defined:

• name: a string identifying a Framebuffer
• width: an integer indicating the width of the framebuffer (optional)
• height: an integer indicating the height of the framebuffer (optional)
• satin:format: only available with Satin, can be one of RGBA8, RGBA16, RGBA16F, or RGBA32F - refer to the OpenGL documentation for more information

The target name minecraft:main is a reserved identifier automatically provided for every shader effect, and identifies the effect's main target (Minecraft's main framebuffer by default). A unique framebuffer will otherwise be created for every declared target.

AuxTarget

An auxiliary target is an object with the following mandatory keys:

• name: a string identifying an auxiliary target.
• id: a string denoting a framebuffer target, or the name of a texture file (with the .png extension omitted) located in assets/minecraft/textures/.

Additionally, if the target refers to a texture, the following keys become mandatory:

• width: an integer indicating the width of the texture object. Does not need to match the actual texture width.
• height: an integer indicating the height of the texture object. Does not need to match the actual texture height.
• bilinear: true if the texture should use linear filtering, false if it should use nearest.

UniformValue

A uniform value is an object with the following mandatory keys:

• name: a string denoting a uniform declared in the program JSON definition.
• values: an array of numbers.

Pass

A pass is an object with the following keys, of which name, intarget, and outtarget are mandatory:

• name: a string identifying a pass. Must map to an existing JSON definition file in assets/minecraft/shaders/program. Satin adds the possibility of using an Identifier format here (domain:program_json).
• intarget: string denoting the input framebuffer. Must resolve to an existing target.
• outtarget: string denoting the output framebuffer. Must resolve to an existing target.
• auxtargets: Contains an array of AuxTarget objects. Optional.
• uniforms: Contains an array of UniformValue objects. Optional.

Example

The most basic non-empty post process definition is as follows:

{
  "targets": [ "swap" ],
  "passes": [
      {
      	"name": "blit",
      	"intarget": "minecraft:main",
        "outtarget": "swap"
      },
      {
          "name": "blit",
          "intarget": "swap",
          "outtarget": "minecraft:main"
      }
  ]
}

If you render this shader, you should see absolutely nothing out of the ordinary. This is because blit simply copies the content of the input framebuffer into the output framebuffer. Thus, this shader effect just copies the main framebuffer's texture into an intermediary swap target and back. However, blit has a ColorModulate uniform that we can use to alter the resulting color:

    "uniforms": [
        { "name": "ColorModulate", "values": [ 1.0, 0.4, 0.7, 1.0 ]}
    ]

Adding the above value to one of the passes will make you see the world in pink!