Encapsulates 2D parameterization for pattern generators. Allows transformations and selection of arbitrary variables bound to primitives. Uses a simple struct to represent bundled dataflow of outputs. @parameters
angle: Rotation angle around origin
scaleS: Frequency of feature in S
scaleT: Frequency of feature in T
offsetS: Offset from origin in S
offsetT: Offset from origin in T
invertS: Flip along S
invertT: Flip along T
primvarS: Name of custom 1D S or 2D ST primvar
primvarT: Name of custom 1D T primvar