DEPRECATED for now. This will require some rewriting to work with sdk changes in recent versions of Bifrost.

Pyfrost

Python embedded in a Bifrost Operator. Created and tested with Maya 2024.1, Bifrost 2.7.1.0, Python 3.11.4.

Built with Python 3.11, a version of which is required to be installed and in the PATH envar.

Installation

1. Copy the Pyfrost folder to the user's compounds directory or other preferred location.

2. Open Maya.env and add the following variables:

    BIFROST_LIB_CONFIG_FILES = <pyfrost location>/PyfrostPackConfig.json
    PYFROST_MODULE_PATH = <pyfrost location>/modules
   

   (if BIFROST_LIB_CONFIG_FILES is defined, append to the existing value using ;)

3. Install a version of Python 3.11, with "Add Python to PATH" checked.

4. Install Numpy: pip install numpy.

5. (Optional) Enable MayaSM by adding the following to userSetup.py:

    import os, sys
    sys.path.append(os.environ["PYFROST_MODULE_PATH"])
    import MayaSM
   

6. (Optional) Pyfrost deals mostly with numpy objects, so it can be useful to have numpy installed to Maya's environment as well:

    "<maya install dir>/bin/mayapy.exe" -m pip install numpy
   

---

Pyfrost Compound Usage

script
    python script to execute

global
    exec in local or global scope

consume_input
    add the pyfrost's output to the input object, or construct a new output object

Predefined objects

np
    Pyfrost imports numpy as np when initialized.

I
    This variable contains the Bifrost input converted to python

O
    An empty dict, any values added to this dict will be converted to properties on the output Bifrost object.
    This can also be re-assigned directly to some other value/type.
    If `O` type is not dict then it will be added to output as a property called 'python_O'

struct(array)
    Designate that a np.ndarray represents a single value with struct data type, ie. vector or matrix.

SMD
    dict shared with Maya (if MayaSM is imported on startup)

Bifrost/Pyfrost Type Conversion

Bifrost -> Python

    Object -> dict
    String -> str
    Simple numeric -> np.generic (numpy scalar)
    Vector -> np.ndarray (1D array)
    Matrix -> np.ndarray (2D array)
    Bifrost array -> np.ndarray
    *other -> None

Python -> Bifrost

    dict -> Object
    str -> String
    np.generic -> Simple numeric
    int -> long
    float -> float
    np.ndarray -> Bifrost array / vector / matrix
    list -> Bifrost array
    tuple -> Bifrost array
    *other -> String (using str(py_object))

Some np.ndarray type conversions are ambiguous, eg. should a float[3] array be converted to a Bifrost float array, or float3 vector. By default the np.ndarray is always converted to an array. struct(array) adds metadata to the array's dtype, designating it as a single value of struct type.

Note

A struct np.ndarray must have a shape matching some Bifrost::Math type, otherwise metadata is ignored and default array conversion is used.

---

MayaSM / Communication with Maya

MayaSM manages a shared memory dictionary for sending commands/data between Pyfrost and Maya.

Pyfrost script:

# In pyfrost SMD can be used without the namespace
SMD["message"] = "hello"

Maya script:

print(MayaSM.SMD["message"])
>>> hello

---

The module includes functions for queuing/executing scripts:

cmd(script)
    Queues a script to be executed as if pasted to the script editor.

mel(script)
    Similar to `cmd` but for mel commands

print(msg, mel_print=True)
    print from Pyfrost to the script editor

warn(msg)
    print from Pyfrost to the script editor as warning

error(msg)
    print from Pyfrost to the script editor as error

Maya still needs to be told when to execute queued commands. This can be done with MayaSM.execPending(). There're 2 options for performing this action automatically.

MayaSM.startTimer(interval=0.1)
    Starts a timer that checks for and executes pending commands at the given interval. Convenient if the expected commands are not time critical.

MayaSM.dgExecutor(graph="")
    Creates an expression node and dummy graph to pull on it. The target graph can be selected or specified by the graph arg.
    The expression calls `MayaSM.execPending()` whenever the given graph evaluates, meaning commands are queued and executed reliably as one evaluation.

---

Bob Explorer

This is simple UI for viewing Bifrost data. If installation step 6. is met, the UI can be opened with:

import BobExplorer
BobExplorer.openControl()