Blender 3D http api

workaround

Description

Simple script file that will allow controlling blender program via an http endpoint
This will start a separate thread from python that will be listening on localhost:8000

There are two modes for the moment:

sync / exec: will execute the commands in a separate thread (not safe) but will return data
async: will schedule the command to be evaluated in the MainThread every second (safe) no data can be return

Warning

Blender team does not recommend accessing the bpy context from a thread different from MainThread.
There are numerous cases where blender will crash with Segmentation fault, hence constantly saving your progress as even scheduling to be executed in the MainThread can cause problems.

Installation

Under Scripting window, create a new text file pass the content of blender_simple_http_api.py

click Run Script ONCE

The running thread that keeps port 8000 in use cannot be killed from the script, hence to make changes or stop the server you need to quit blender

Usage

To make the apy as flexible as possible there is no JSON serialization in the response, but it can be achieved using json.dumps

SYNC

POST Retrieve raw python data curl --data "dir(bpy.data.objects['Cube'])" localhost:8000/sync
POST Retrieve as json curl --data "json.dumps(dir(bpy.data.objects['Cube']))" localhost:8000/sync
POST Retrieve X location of an object curl --data "bpy.data.objects['Cube'].location.x" localhost:8000/sync
GET Object property value ( will execute the same command as the one above ) curl localhost:8000/Cube/location/x Expected: 0.0
GET Object properties curl localhost:8000/Cube/location Expected: <Vector (3.1146, 8.0631, 4.8566)>
POST Move object ( assignment ) curl --data "bpy.data.objects['Cube'].location.x += 0.05" localhost:8000/exec
POST Accessing actions that depends on context view: FAILS ( works in python interpreter ) curl --data "bpy.ops.object.editmode_toggle()" localhost:8000/sync >>> throws error as context is not VIEW 3D

ASYNC

All commands are executed in main Thread that should avoid Segmentation faults but no data can be retrieved as there is no pub-sub queue implementation

This is still crashing blender as it is missing the context ( know bug ?? ) curl --data "bpy.ops.mesh.primitive_cube_add(location=(4,-3,6))" localhost:8000/async
Add object cube workaround curl --data "bpy.ops.mesh.primitive_cube_add({'window': bpy.context.window_manager.windows[0], 'screen': bpy.context.window_manager.windows[0].screen}, location=(4,-3, 6))" localhost:8000/async

DIRECT METHOD CALL

You can store functions in driver_namespace object and then call the function directly passing the content of the POST as a single string argument. You can change/update the function in every "Run Script"

Example: Create a complex function and save the reference in bpy.app.driver_namespace

import bpy
import threading
 
def cube(args_str):
    print(threading.current_thread().name, "Executing cube function")
    window = bpy.context.window_manager.windows[0]
    ctx = {'window': window, 'screen': window.screen}
    location_parts = args_str.split(',')
    bpy.ops.mesh.primitive_cube_add(ctx, location=(float(location_parts[0]),float(location_parts[1]),float(location_parts[2])))
 
bpy.app.driver_namespace["cube"] = cube

Using POST pass the values as a single string that you need to split inside the function

curl --data "4,-3,6" localhost:8000/cube

klusht/blender-http-api