Basilisp Blender Integration

Basilisp is a Python-based Lisp implementation that offers broad compatibility with Clojure. For more details, refer to the documentation.

Overview

basilisp-blender is a Python library designed to facilitate the execution of Basilisp Clojure code within Blender and manage an nREPL server for interactive programming. This library provides functions to evaluate Basilisp code from Blender's Python console, file or Text Editor and to start an nREPL server, allowing seamless integration and communication with Basilisp.

Installation

To install basilisp-blender, use pip from Blender's Python console:

import pip
pip.main(['install', 'basilisp-blender'])

Usage

Evaluating Basilisp Code

From a Code String

To evaluate a Basilisp code string:

from basilisp_blender.eval import eval_str

eval_str("(+ 1 2)")
# => 3

From a File

To evaluate Basilisp code from a file:

from basilisp_blender.eval import eval_file

eval_file("path/to/your/code.lpy")

From Blender’s Text Editor

To evaluate Basilisp code contained in a Blender text editor block:

from basilisp_blender.eval import eval_editor

# Replace `text_block` with your Blender text block name
eval_editor("<text-block-name>")

Starting an nREPL Server

To start an nREPL server within Blender:

from basilisp_blender.nrepl import server_start

shutdown_fn = server_start(host="127.0.0.1", port=8889)

The host and port arguments are optional. If not provided, the server will bind to a random local port. It will also creates an .nrepl-port file in the current working directory containing the port number it bound to.

The return value is a function that you can call without arguments to shut down the server. Note that all nREPL client sessions must be closed before this function can succesfullyl shutdown the server.

For a more convenient setup, you can specify to output .nrepl-port file to your Basilisp's project's root directory. This allows some Clojure editor extensions (such as CIDER or Calva) to automatically detect the port when connect'ing to the server:

from basilisp_blender.nrepl import server_start

shutdown_fn = server_start(nrepl_port_filepath="<project-root-path>/.nrepl-port")

Replace <project-root-path> with the path to your project's root directory.

Examples

Also see the examples directory of this repository.

Here is an example of Basilisp code to create a torus pattern using the bpy Blender Python library:

(ns torus-pattern
  "Creates a torus pattern with randomly colored materials."
  (:import bpy
           math))

(def object (.. bpy/ops -object))
(def materials (.. bpy/data -materials))
(def mesh (.. bpy/ops -mesh))


(defn clear-mesh-objects []
  (.select-all object ** :action "DESELECT")
  (.select-by-type object ** :type "MESH")
  (.delete object))

(clear-mesh-objects)

(defn create-random-material []
  (let [mat (.new materials ** :name "RandomMaterial")
        _ (set! (.-use-nodes mat) true)
        bsdf (aget (.. mat -node-tree -nodes) "Principled BSDF")]

    (set! (-> bsdf .-inputs (aget "Base Color") .-default-value)
          [(rand) (rand) (rand) 1])
    mat))

(defn create-torus [radius tube-radius location segments]
  (.primitive-torus-add mesh **
                        :major-radius radius
                        :minor-radius tube-radius
                        :location location
                        :major-segments segments
                        :minor-segments segments)
  (let [obj (.. bpy/context -object)
        material (create-random-material)]
    (-> obj .-data .-materials (.append material))))

#_(create-torus 5, 5, [0 0 0] 48)

(defn create-pattern [{:keys [layers-num radius tube-radius]
                       :or {layers-num 2
                            radius 2
                            tube-radius 0.2}}]
  (let [angle-step (/ math/pi 4)]
    (dotimes [i layers-num]
      (let [layer-radius (* radius (inc i))
            objects-num (* 12 (inc i))]
        (dotimes [j objects-num]
          (let [angle (* j angle-step)
                x (* layer-radius (math/cos angle))
                y (* layer-radius (math/sin angle))
                z (* i 0.5)]
            (create-torus (/ radius 2) tube-radius [x y z] 48)))))))

(create-pattern {:layers-num 5})

Troubleshooting

If you encounter unexplained errors, enable DEBUG logging and save the output to a file for inspection. For example:

import logging
from basilisp_blender import log_level_set

log_level_set(logging.DEBUG, filepath="bblender.log")

Blender scripting is not hread safe. As a result, the nREPL server cannot be started into a background thread and still expect calling bpy functions to work without corrupting its state.

To work around this limitation, the nREPL server is started in a thread, but client requests are differed into a queue that will be executed later by a bpy custom timer function. The function is run in the main Blender loop at intervals of 0.1 seconds, avoiding parallel operations that could affect Blender's state.

If necessary, you can adjust this interval to better suit your needs by passing the interval_sec argument to the server_start function:

from basilisp_blender.nrepl import server_start

shutdown_fn = server_start(port=8889, interval_sec=0.05)

Development

This package uses the Poetry tool for managing development tasks.

Testing

You can run tests using the following command:

$ poetry run pytest 

Integration testing

To run integration tests, set the $BB_BLENDER_TEST_HOME environment variable to the root directory of the Blender installation where the development package is installed. See next section on how to facilitate the installation.

$ export BB_BLENDER_TEST_HOME="~/blender420"
# or on MS-Windows
> $env:BB_BLENDER_TEST_HOME="c:\local\blender420"

Then run the integration tests with

$ poetry run pytest -m integration

Installing Blender and the Development Package

To download and install Blender in the directory specified by $BB_BLENDER_TEST_HOME, use:

$ poetry run python scripts/blender_install.py 4.2.0

To install the development version of the package at the same location, use:

$ poetry build                            # build the package
$ poetry run python scripts/bb_install.py # install it in Blender