Scripts – Blender – Interplanety

How to check what version of Python interpreter is used in Blender

To find what Python interpreter version is used in current Blender version type the following commands in Python Console window in Blender:

import sys
print(sys.version_info)

# sys.version_info(major=3, minor=7, micro=0, releaselevel='final', serial=0)

import sys

print(sys.version_info)

# sys.version_info(major=3, minor=7, micro=0, releaselevel='final', serial=0)

It means that the version of Python used in Blender is 3.7.0.

To make it more readable type the following command:

print('.'.join(map(str, sys.version_info[:3])))
# 3.7.0

1 2	print('.'.join(map(str, sys.version_info[:3]))) # 3.7.0

or with full info:

print(sys.version)
# 3.7.0 (default, Aug 26 2018, 16:05:01) [MSC v.1900 64 bit (AMD64)]

1 2	print(sys.version) # 3.7.0 (default, Aug 26 2018, 16:05:01) [MSC v.1900 64 bit (AMD64)]

Porting add-on from Blender 2.7 to Blender 2.8

In the latest version 2.8 of Blender developers have made many changes in API, so all the scripts and add-ons written for earlier Blender versions (2.7 and below) have stopped working. To run your add-ons in the new Blender 2.8, you need to port them – correct their code to work properly with the new Blender API.

To enable your add-on in Blender 2.80 you have to make the following changes in code:

Continue reading “Porting add-on from Blender 2.7 to Blender 2.8”

Using Microsoft Visual Studio Code as external IDE for writing Blender scripts/add-ons

Blender has its own built-in text editor for writing scripts and add-ons, but it’s much convenient to develop them in external IDEs that provide the user with more features such as autocomplete, syntax highlighting, integration with version control systems and other tools that make development faster and easier.

One of these IDEs is Visual Studio Code from Microsoft. This is a free universal environment that supports development with various programming languages, including the Blender API language – Python.

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Learning loops

In general, the “loop” is usually a sequential selection of several points, edges or polygons of a mesh.

However, there is an element in the mesh structure, which is also called a “loop”. It is a combination of one vertex with one edge of the mesh. Let’s try to learn what these “loops” are for.

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How to pass command line arguments to a Blender python script or add-on

When starting Blender from the console it processes all parameters passed through the command line. However, some scripts and add-ons for proper work may require specifying their unique command line arguments. If you specify such additional parameters in the command line, Blender will also try to process them, which is likely to result in an error. Blender provides a special way to exclude such arguments from own processing.

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Creating radio buttons in the Blender add-ons interface

State switches so-called “radio buttons” are used in the case to limit the choice by one value from several available ones. There are a lot of such buttons in the Blender interface, for example, switching between RGB and BW rendering modes or setting the texture mapping mode. Such buttons can be created in the Blender add-ons interface too.

Let’s create our own radio button switcher.

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How to programmatically check if the operator is registered in Blender API

Single add-on or script can contain several different operators, and not all of them may be registered in the API by the register() function. To verify that the required operator is registered in the Blender API, run the following command:

hasattr(bpy.types, bpy.ops._operator_bl_idname_.idname())

1	hasattr(bpy.types, bpy.ops._operator_bl_idname_.idname())

Where:

_operator_bl_idname_ – the text value of the bl_idname operator property.

For example for an operator:

class TestOperator(bpy.types.Operator):
    bl_idname = 'test.operator'
    bl_label = 'Test operator'

    def execute(self, context):
        pass

class TestOperator(bpy.types.Operator):

bl_idname = 'test.operator'

bl_label = 'Test operator'

def execute(self, context):

pass

the command will look like this:

hasattr(bpy.types, bpy.ops.test.operator.idname())

1	hasattr(bpy.types, bpy.ops.test.operator.idname())

How to programmatically check if the Blender add-on is registered

To start working every Blender add-on must be registered by setting up the checkbox before add-on name in the User Preferences window – Add-ons page.

To programmatically find out if the required add-on is registered, run the following command:

'add-on_name' in the file bpy.context.user_preferences.addons

1	'add-on_name' in the file bpy.context.user_preferences.addons

Where:

add-on_name – the name of the add-on file (without the .py extension) or the name of the add-on package, if it was installed from the package.

How to install and uninstall Blender add-on via python API

Blender add-ons installation and uninstallation can be managed through the python API. Use the following commands in a script:

To deactivate the add-on:

bpy.ops.wm.addon_disable(module = 'add-on name')

1	bpy.ops.wm.addon_disable(module = 'add-on name')

To uninstall the add-on:

bpy.ops.wm.addon_remove(module = 'add-on name')

1	bpy.ops.wm.addon_remove(module = 'add-on name')

Continue reading “How to install and uninstall Blender add-on via python API”

Mesh Custom Properties editing through the Blender API

New mesh Custom Property can be created through the Blender python API by executing the following code:

bpy.data.objects['object_name']['property_name'] = property_value

1	bpy.data.objects['object_name']['property_name'] = property_value

with:

object_name – name of the mesh
property_name – new custom property name
property_value – value of this new property

After executing this command, the new property will be created and will be available in the Properties window – Object panel – Custom Properties sub-panel.

Like any object custom properties, the created property has a number of parameters that can be accessed by clicking the Edit button. These parameters can also be changed through the API.

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Working with UV-Maps through the Blender API

Active (selected) UV-Map:

bpy.context.active_object.data.uv_layers.active

1	bpy.context.active_object.data.uv_layers.active

Access to the active UV-Map by its name:

bpy.context.active_object.data.uv_layers['UVMap']

1	bpy.context.active_object.data.uv_layers['UVMap']

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Creating pop-up panels with user UI in Blender add-on

In addition to common panels (N/T/Properties) and their sub-panels, to display the user interface elements while developing Blender add-ons you can also use pop-up panels appearing on the screen when a user presses a certain key combination or perform any action. The simplest example of such panels is the panel that appears when the f6 key is pressed immediately after adding an object (shift+a) to the scene.

Blender API provides developers the ability to create such panels for their add-ons. Let’s consider the creating of a pop-up panel as an example of the “Message box” window.

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Active objects access

How to access the active (selected) objects through the Blender Python API from scripts/add-ons:

The active window (in which current action occurs):

bpy.context.area.spaces.active

1	bpy.context.area.spaces.active

The active scene:

bpy.context.screen.scene

1	bpy.context.screen.scene

The active (selected) mesh:

bpy.context.active_object

1	bpy.context.active_object

The active (selected) material node (in the NODE_EDITOR window):

bpy.context.active_object.active_material.node_tree.nodes.active

1	bpy.context.active_object.active_material.node_tree.nodes.active

The active (selected) material node (in the COMPOSITING window):

bpy.context.scene.node_tree.nodes.active

1	bpy.context.scene.node_tree.nodes.active

The current text in TEXT_EDITOR window:

bpy.context.area.spaces.active.text.as_string()

1	bpy.context.area.spaces.active.text.as_string()

The active (selected) UV-Map:

bpy.context.active_object.data.uv_layers.active

1	bpy.context.active_object.data.uv_layers.active

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How to get Blender objects structure

Writing scripts in Blender we often need to know the full list of object properties to access them through the Blender API. Consider how we can get a list of available object methods and properties.

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Working with MySQL database from Blender

Storing data in a remote database has become common practice in the development of software products. Blender is no exception. Writing scripts and add-ons, the developer may need to access the database to retrieve from it or write to it the necessary information. MySQL today is one of the most common and widely available databases and is well suited for working with Blender.

The interaction between Blender and MySQL database through the Blender Python API is not difficult, but it needs some preparation before stating:

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Binding to timeline frames

Sometimes when creating an animation it is necessary to perform some actions according to the timeline or, the same, to the current animation frame number. Binding animation to timeline frames in Blender is possible using the built-in Python API.

As an example, let’s make a simple animation which turns one of the letters of any text from lowercase to uppercase in series.

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Deleting nodes from compositing via script

To clear compositing window (completely remove all nodes from it), run the following code:

import bpy
nodesField = bpy.context.scene.node_tree
for currentNode in nodesField.nodes:
    nodesField.nodes.remove(currentNode)

import bpy

nodesField = bpy.context.scene.node_tree

for currentNode in nodesField.nodes:

nodesField.nodes.remove(currentNode)

How to check errors if Blender closes together with system console window

Sometimes when debugging scripts or add-ons, errors not only interrupt the code execution but also causes the complete closure of Blender together with its system console. This case its impossible to check errors and view errors messages.

To find a failure, Blender can be started from the command line interpreter cmd. In this case, Blender output log is redirected to the cmd window which, when the program falls due to errors, not closed. If Blender closes all error messages stay available to check in the cmd window.

Running Blender from command line interpreter cmd

To start Blender from a command line interpreter:

Start the interpreter ( “Start” – Run – cmd)
In the cmd window type the full path to the installed Blender. For example: C:\”Program Files”\blender-2.78a-windows64\blender.exe

Part of the way contains spaces must be enclosed in double quotes – like “Programm Files” in this example.

Using external IDE PyCharm for writing Blender scripts

Blender has an internal text editor to write scripts on Python language. However, this editor is much inferior to specially designed for writing code IDEs. There is no satisfactory autocomplete, comfortable syntax lighting, possibility to organize projects in Blender internal text editor – all those things that determine the speed and ease of code writing. However, it is not difficult to connect and use an external IDE for writing Blender scripts.

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