Selecting scene camera with shortcode
It can be difficult to quickly find and select the scene camera from many other objects in large scenes. However, we can make an operator and assign its call to a hotkey to find the scene camera in a moment.
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Python
Operators for globally hiding objects in all project scenes
To hide an object in the 3D Viewport window for the current scene we use the “object.hide_view_set” operator, which calls when we clicking the icon with an “eye” in the outliner. However, to hide the object in the viewport for all scenes of the project at once (clicking on the icon with the “monitor” image) a special operator is not provided. We can make it ourselves.
Operators for globally hiding objects in all project scenesRead More »
Showing an object dynamic property on a UI panel
The Blender API recommends creating custom object properties through the predefined bpy.props classes. For example, the bpy.props.IntProperty class is used to add an integer property. These properties are convenient, work well, and are easy to display on the user interface panels.
How to apply transformations to a mesh with the Blender Python API
To apply all transformations to an object, all its vertices must be multiplied by its global matrix, the matrix itself must be made identity.
To apply all transformations to the active mesh, we need to execute the following:
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import bpy obj = bpy.context.object matrix = obj.matrix_world.copy() for vert in obj.data.vertices: vert.co = matrix @ vert.co obj.matrix_world.identity() |
Message Bus
In Blender API there is a module that we can use to track the changes of any object’s properties available through the Python API. This module names “Message Bus”.
Let’s look at how we can make an event handler function to track changes to a property. For example – the location of the 3D cursor.
Origin to active
A simple script for transferring the origin of all selected objects to the origin of the active object.
Setting colors for Blender collections with the Python API
Since Blender 2.9, the ability to assign color tags has been added for collections. Collection with such tag is displaying in a specific color in the outliner.
The collection color tag value is stored in its “color_tag” property. To change the color label of a collection, we need to assign a certain value to this property.
For example, to mark the current active collection in green:
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bpy.context.collection.color_tag = 'COLOR_04' |
Setting colors for Blender collections with the Python APIRead More »
How to add a new material slot
To add a new slot to the material slots for an object:
- We can use the operator object.material_slot_add
Operator for toggling checkboxes
The “wm.context_toggle” operator is used to toggle checkboxes in the Blender interface. We can configure fast switching of any checkboxes in any windows and panels with this operator.
As an example, let’s configure the checkbox which enables/disables displaying the viewport wireframe.
Accessing the active brush through the Blender Python API
To get the currently active brush in “Sculpt” mode with the Blender Python API we can use the following command:
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bpy.context.tool_settings.sculpt.brush # bpy.data.brushes['SculptDraw'] |
How to create collection through the Blender Python API
To create a new collection in the scene using the Blender Python API, we need to execute the following:
How to create collection through the Blender Python APIRead More »
How to find which collection contains the desired object
If the object you need is located in a hidden collection, it can be difficult to find it in large scenes.
To find out in which collection the desired object is located by its type, we need to execute the following. For example for cameras:
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[(obj.name, obj.users_collection) for obj in bpy.data.objects if obj.type=='CAMERA'] # [('Camera', (bpy.data.collections['camera'],))] |
This code will return a list of cameras and collections in which they are located.
Context override
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:
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bpy.ops.wm.toolbar() # {'CANCELLED'} |
or it will fail with an error message about the incorrect context:
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bpy.ops.view3d.background_image_add() # RuntimeError: Operator bpy.ops.view3d.background_image_add.poll() failed, context is incorrect |
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”.
How to change current tool through the Blender Python API
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:
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import bpy bpy.ops.wm.tool_set_by_id(name='builtin.select_circle') |
How to change current tool through the Blender Python APIRead More »
How to import a Python module by the absolute path
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.
How to import a Python module by the absolute pathRead More »
How to link a mesh to an armature bone with maintaining its current position
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:
How to link a mesh to an armature bone with maintaining its current positionRead More »
How to align an armature bone to a bone from another armature
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:
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import bpy armature_to = bpy.data.objects['Armature'] armature_from = bpy.data.objects['Armature.001'] armature_from.matrix_world = armature_to.matrix_world armature_from.pose.bones[0].matrix = armature_to.pose.bones[0].matrix |
After executing this code, the first bone of the “Armature.001” will be moved to the position of the first bone of the “Armature”.
How to calculate the Bounding Sphere for selected objects
Most often, for quick simplified calculations with the object’s geometry, their Bounding Boxes are used – the minimum parallelepiped into which this object is inscribed. But sometimes the Bounding Sphere – the minimum sphere into which an object can be inscribed – can provide greater accuracy and simplify the calculations. While the location and size of the object’s Bounding Box is available in Blender at once, the Bounding Sphere we need to calculate manually
Let’s write a function that, based on the object list, returns the coordinates of the center of their Bounding Sphere and its radius.
How to calculate the Bounding Sphere for selected objectsRead More »
Matrix inverting features
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
Multiline text in Blender interface panels
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.
How to get the number of triangles in a mesh
To get the number of vertices, edges, and polygons in a mesh, we can simply take their amount from the desired data block: “vertices”, “edges”, and “polygons”. However, there is no special data block for triangles in the mesh structure.
To get the number of triangles in the mesh, we need to execute the following code:
Vertical and horizontal camera FOV angles
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).
Blender 2.92 autocomplete
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
Features of using the scale matrix
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:
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from mathutils import Matrix scale_matrix = Matrix.Scale(SCALE_VALUE, MATRIX_SIZE, AXIS) |