Root Transforms

Adding the transform entry at the top level of a model JSON suggests to the loader that a transformation should be applied to all geometry right before the rotations in the blockstate file in the case of a block model, and before the display transforms in the case of an item model. The transformation is available through IGeometryBakingContext#getRootTransform() in IUnbakedGeometry#bake().

Custom model loaders may ignore this field entirely.

The root transforms can be specified in two formats:

1. A JSON object containing a singular matrix entry containing a raw transformation matrix in the form of a nested JSON array with the last row omitted (3*4 matrix, row major order). The matrix is the composition of the translation, left rotation, scale, right rotation and the transformation origin in that order. Example demonstrating the structure:

   "transform": {
       "matrix": [
           [ 0, 0, 0, 0 ],
           [ 0, 0, 0, 0 ],
           [ 0, 0, 0, 0 ]
       ]
   }
2. A JSON object containing any combination of the following optional entries:
   • origin: origin point used for the rotations and scaling
   • translation: relative translation
   • rotation or left_rotation: rotation around the translated origin to be applied before scaling
   • scale: scale relative to the translated origin
   • right_rotation or post_rotation: rotation around the translated origin to be applied after scaling

Element-wise specification

If the transformation is specified as a combination of the entries mentioned in option 4, these entries will be applied in the order of translation, left_rotation, scale, right_rotation.
The transformation is moved to the specified origin as a last step.

{
    "transform": {
        "origin": "center",
        "translation": [ 0, 0.5, 0 ],
        "rotation": { "y": 45 }
    },
    // ...
}

The elements are expected to be defined as follows:

Origin

The origin can be specified either as an array of 3 floating point values representing a three-dimensional vector: [ x, y, z ] or as one of the three default values:

• "corner" (0, 0, 0)
• "center" (.5, .5, .5)
• "opposing-corner" (1, 1, 1)

If the origin is not specified, it defaults to "opposing-corner".

Translation

The translation must be specified as an array of 3 floating point values representing a three-dimensional vector: [ x, y, z ] and defaults to (0, 0, 0) if not present.

Left and Right Rotation

The rotations can be specified in any one of the following four ways:

• Single JSON object with a single axis => rotation degree mapping: { "x": 90 }
• Array of an arbitrary amount of JSON objects with the above format (applied in the order they are specified in): [ { "x": 90 }, { "y": 45 }, { "x": -22.5 } ]
• Array of 3 floating point values specifying the rotation in degrees around each axis: [ 90, 180, 45 ]
• Array of 4 floating point values specifying a quaternion directly: [ 0.38268346, 0, 0, 0.9238795 ] (example equals 45 degrees around the X axis)

If the respective rotation is not specified, it will default to no rotation.

Scale

The scale must be specified as an array of 3 floating point values representing a three-dimensional vector: [ x, y, z ] and defaults to (1, 1, 1) if not present.