Tag: Python

Some Blender operators can only be called from the workspace for which they are intended.

If you call from the Python console, for example, an operator intended only for working in the 3D Viewport area, the operator will not be executed:

or it will fail with an error message about the incorrect context:

However, we can still execute operators from a non-native working area. To do this, we can pass the first implicit parameter to any operator – a pointer to the context of the area in which this operator should be executed. This parameter commonly named the “overridden context”.

Continue reading “Context override”

To switch the active tool from the T-panel in the 3D viewport window, we need to call the appropriate operator and pass the “idname” of the required tool in its “name” parameter.

For example, to enable the “Select Circle” selection toll, we need to call:

Continue reading “How to change current tool through the Blender Python API”

Modules used in Blender scripts and add-ons are located in the same directory as the script or add-on, or in the Blender installation directory by the “blender_version\python\lib\” path. However, it is possible to load a module located elsewhere on the hard drive.

To do this, we need to load the module by its absolute path.

Continue reading “How to import a Python module by the absolute path”

To link a mesh to an armature bone that the mesh retains its current position through the Blender Python API, we need to execute the following code:

Continue reading “How to link a mesh to an armature bone with maintaining its current position”

To accurately align the bone of one armature with the bone of another armature, we need to correlate the global armature matrices and the local pose-bone matrices.

To do this, we need to execute the following:

After executing this code, the first bone of the “Armature.001” will be moved to the position of the first bone of the “Armature”.

An attempt to invert the transformation matrix with the inverted() method can be failed if, for example, some constraint affects the object for which the initial matrix is calculated.

In this case, Blender will generate an error:

ValueError: Matrix.invert(ed): matrix does not have an inverse

Continue reading “Matrix inverting features”

Unfortunately, Blender’s interface does not support word wrapping and multi-line text blocks. Text lines that are too long to be displayed in the panel are cut off. However, multiline text can still be displayed on the panel using several text elements instead of one.

First, let’s create a simple panel in the N-panel of the 3D Viewport window and place a label element with the desired text on it.

Continue reading “Multiline text in Blender interface panels”

Cameras in Blender are always defined by two FOV angles – vertical and horizontal.

One of these angles is always set by the user through the camera parameter – Feild of View (or a combination of the Focal Length and Sensor Width parameters).

Continue reading “Vertical and horizontal camera FOV angles”

Blender Python API autocomplete modules: fake-bpy-modules by Nutti update – added branch for Blender 2.92.

Last release: 2021.03.04.

Author GitHub: https://github.com/nutti/fake-bpy-module

Only files (without pip installation) https://github.com/Korchy/blender_autocomplete

To manipulate object transformations with matrices, Blender includes the “mathutils” module in which the “Matrix” class is defined. With this class, you can simply create the necessary transformation matrices – translation, rotation, and scale.

The following command is used to create a scale matrix:

Continue reading “Features of using the scale matrix”

When referring to the mesh geometry – its vertices, edges, and polygons, Blender operates with the original data without the usage of modifiers added to the object.

For example, the number of vertices of the active object, we can get with the following command:

And it will be returned without considering the object’s Subdivision modifier, which modifies the mesh’s geometry, increasing it.

Continue reading “How to get mesh data with modifiers”

In order to navigate to an URL-address from Blender – to open the required address in the browser, we can use the system operator “wm.url_open”.

To demonstrate this let’s create a simple tab in the N-panel with a single button, by clicking on which the required page will be opened in the browser.

Continue reading “How to make an url button in Blender interface”

To have the access to the current context, for example, to work with operators, and to the scene data, for example, to work with meshes, we use two predefined structures from the Blender Python API: “bpy.context” and “bpy.data”.

For example, we can pass them to a function:

However, in the “bpy.context” structure there is a “blend_data” pointer that links to the scene data. With this pointer, we can access scene data without passing it separately and explicitly.

In Blender, we can select and deselect mesh vertices through the “select” property for each vertex.

However, to deselect a vertex, it is not enough to set it’s “select” property to “False”

Continue reading “How to deselect mesh vertices”