Blender 3D: tutorials, articles, tips, notes
To set mesh (object) as active in Blender 2.8 Python API the “context.view_layer” is used instead of “context.scene”.
When trying to make object active with “bpy.context.scene.objects.active” Blender throws an error:
AttributeError: bpy_prop_collection: attribute “active” not found
To make object active in Blender 2.8 use the following code:
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obj = bpy.context.window.scene.objects[0] bpy.context.view_layer.objects.active = obj # 'obj' is the active object now |
According to Blender 2.8 Python API changes mesh (object) can be selected with using getters and setters.
When trying to check the selected status of the mesh through the “bpy.context.active_object.select” property, Blender throws an error:
AttributeError: ‘Object’ object has no attribute ‘select’
To check whether an object is selected in Blender 2.8 use a getter:
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bpy.context.active_object.select_get() # True |
To select an object in Blender 2.8 use a setter:
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bpy.context.active_object.select_set(state=True) |
To unselect an object use the same setter:
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bpy.context.active_object.select_set(state=False) |
To find what Python interpreter version is used in current Blender version type the following commands in Python Console window in Blender:
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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:
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print('.'.join(map(str, sys.version_info[:3]))) # 3.7.0 |
or with full info:
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print(sys.version) # 3.7.0 (default, Aug 26 2018, 16:05:01) [MSC v.1900 64 bit (AMD64)] |
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”
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.
To check is an attribute/property of any Blender object (mesh, node, modifier, etc.) read-only:
<object> .is_property_readonly (‘<property name>’)
<object> .bl_rna.properties [‘<property name>’]. is_readonly
For example, for the “is_editmode” mesh property (is the mesh in edit mode or not):
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bpy.context.active_object.data.is_property_readonly('is_editmode') # True bpy.context.active_object.data.bl_rna.properties['is_editmode'].is_readonly # True |
A complete list of add-ons installed in Blender we can get using the addon_utils:
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import addon_utils print(addon_utils.modules()[:]) # <module 'space_view3d_3d_navigation' from ... |
Having the add-ons list, we can get the version of the desired add-on by its name with the following code:
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import addon_utils print([addon.bl_info.get('version', (-1,-1,-1)) for addon in addon_utils.modules() if addon.bl_info['name'] == 'ADD-ON_NAME'][0]) # (1,4,0) |
Where the ADD-ON_NAME is the name of the desired add-on.
If the add-on is missing a version indication, the default result will be returned.
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# (-1,-1,-1) |
Change the mesh_select_mode property to switch in mesh edit mode between vertex, edge and polygon selection mode in Blender.
For vertex selection mode:
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bpy.context.tool_settings.mesh_select_mode = (True, False, False) |
Edge selection mode:
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bpy.context.tool_settings.mesh_select_mode = (False, True, False) |
And face selection mode:
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bpy.context.tool_settings.mesh_select_mode = (False, False, True) |
The multi-select mode is enabled too. For example for vertex and face selection mode:
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bpy.context.tool_settings.mesh_select_mode = (True, False, True) |
In BMesh for vertex, edge and face selection mode:
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bm.select_mode = {'VERT'} bm.select_mode = {'EDGE'} bm.select_mode = {'FACE'} |
For multi-select in BMesh:
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bm.select_mode = {'VERT', 'EDGE', 'FACE'} |
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.
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.
Continue reading “How to pass command line arguments to a Blender python script or add-on”
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.
Continue reading “Creating radio buttons in the Blender add-ons interface”
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:
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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:
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class TestOperator(bpy.types.Operator): bl_idname = 'test.operator' bl_label = 'Test operator' def execute(self, context): pass |
the command will look like this:
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hasattr(bpy.types, bpy.ops.test.operator.idname()) |
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:
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'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.
It is convenient to use the following system for debugging developing multi-file Blender add-ons. But it has one drawback: modules imported in __init__.py file becomes available only after the file running (after the execution of the register() function). This means that any access to the imported modules before they are registered will cause an error. This is not critical in most cases, but it will cause a problem if, for example, in one imported module is used inheritance from the class, described in the other imported module, because the classes descriptions are processed before the add-on registration.
To get more freedom working with imported modules, we can use another way to debug the add-on – do not run the add-on directly from the development directory, but install it in Blender and check its “live” work. However, manual add-on reinstallation requires a set of routine actions, which complicates such sort of debugging. This issue can be solved by reinstalling the add-on in automatic mode.
Continue reading “Debugging multifile Blender add-on by quick reinstall”
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:
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bpy.ops.wm.addon_disable(module = 'add-on name') |
To uninstall the add-on:
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bpy.ops.wm.addon_remove(module = 'add-on name') |
Continue reading “How to install and uninstall Blender add-on via python API”
New mesh Custom Property can be created through the Blender python API by executing the following code:
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bpy.data.objects['object_name']['property_name'] = property_value |
with:
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.
Continue reading “Mesh Custom Properties editing through the Blender API”
Active (selected) UV-Map:
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bpy.context.active_object.data.uv_layers.active |
Access to the active UV-Map by its name:
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bpy.context.active_object.data.uv_layers['UVMap'] |
Continue reading “Working with UV-Maps through the Blender API”
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.
Continue reading “Creating pop-up panels with user UI in Blender add-on”
BIS (Blender Interplanety Storage) add-on release.
Finally, I finished it. It’s release now!
BIS (Blender Interplanety Storage) add-on intermediate update to v.0.0.3
The addon is almost in the prerelease state.
To make a release, it was left to clean up a bit the server (site) side – increase the previews size, add tags and node names editing, make a separate list for saved texts. And also test the add-on with complex materials.
DownloadHow to access the active (selected) objects through the Blender Python API from scripts/add-ons:
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bpy.context.area.spaces.active |
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bpy.context.screen.scene |
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bpy.context.active_object |
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bpy.context.active_object.active_material.node_tree.nodes.active |
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bpy.context.scene.node_tree.nodes.active |
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bpy.context.area.spaces.active.text.as_string() |
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bpy.context.active_object.data.uv_layers.active |
BIS (Blender Interplanety Storage) add-on intermediate update to v.0.0.2
Blender Interplanety Storage (BIS) – the online material (shader) storage add-on for Blender 3D creation. With the BIS add-on, you can save materials (groups of nodes) to the online personal library and then convenient search and upload them. Saved materials are available from any computer through the add-on installed in Blender.
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.
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: