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Blender 4.2: Python API

Add-on Packaging

With the new extensions platform, there is also a new method for packaging add-ons. It uses a separate blender_manifest.toml file instead of bl_info embedded in the script. See the extensions user manual for details.

The old packaging still works but is considered legacy, and add-ons are recommended to switch to the new manifest file.

Additions

Online Access

  • bpy.app.online_access is a read-only property to check whether Blender (and add-ons) is expected to access the internet.
  • Add-ons are expected to check for this property before accessing the internet. See documentation.
  • Also available is bpy.app.online_access_override which tells whether Blender was launched with --offline-mode / --online-mode.

bpy.utils Module

  • The EXTENSIONS option has been added to bpy.utils.user_resource() (dc9430c480).
  • Add bpy.utils.register_cli_command & unregister_cli_command so scripts can define their own command line functionality via (-c, --command). (9372e0dfe0)

Animation

  • rna_struct.keyframe_insert() now has a new, optional keyword argument keytype to set the key type (1315991ecb). This makes it possible to set the new key's type directly. Example: bpy.context.object.keyframe_insert("location", keytype='JITTER').

Layout Panels

Added support for layout panels for operator properties drawing, in popups, redo panel and the file browser sidebar. Add-ons are recommended to use panels for organizing properties now, to follow Blender user interface conventions. (aa03646a74, 02681bd44d)

Exporters

Exporter add-ons can add support for the new Collection Exporters. This requires a FileHandler with bl_export_operator, and a string property named collection on the operator to indicate the collection to export. See the FBX and glTF add-ons for an example.

  • Window.modal_operators provides a list of running modal operators. (#122193)
  • Modal operator can add MODAL_PRIORITY to bl_options to handle events before other modal operators. (6efd7a6a50)

Handlers

  • Render: include info string for "render_stats" handler (fcc481a407)

Breaking changes

Statically Typed IDProperties

IDProperties have never be statically typed before, modifying their type was (way) too easy from Python. A mere assignment of a float value to an IDProperty from Python code would e.g. convert that property to a 'double' one. This was especially problematic for system-defined IDProperties (i.e. these used as backend storage for internal Blender data, like geometry node modifier properties, or Python-defined 'dynamic RNA' properties). It would also easily break library overrides, which cannot give useful results when the type of the reference and override data differs.

The following IDProperties now have a fixed, static type that cannot be modified from the python API. In array (vector) cases, the length is also considered as part of the type, and therefore fixed.

  • System-defined:
    • Geometry Node modifier settings IDProperties.
    • Python-defined properties (through the bpy.props. module).
  • User-defined:
    • Properties created from the UI (Custom Properties panel, in the Properties editor), when their Library Overridable option is enabled.

When assigning a value to such property, a 'reasonable conversion' is attempted if possible (e.g. an integer can be converted to a float, but a float cannot be assigned to an integer IDProperty), otherwise the assignment fails.

Note

Technically, this is a breaking change. In particular in Geometry Nodes modifier case, where the 'expected' way to access these data from python is currently through 'raw' IDProperty path. However, practically, no 'valid' usages of the IDProperties should be broken by it.

Further details can be found in the design task.

Commits: 4d1fe98604, b278e37f70, 76f03eb141, 9c41bf4fa2

bpy.utils Module

  • The AUTOSAVE option has been removed from bpy.utils.user_resource() (6bfc8612bf).

Render Settings

  • Motion Blur settings have been de-duplicated between Cycles and EEVEE and moved to bpy.types.RenderSettings. (74b8f99b43)
    • scene.cycles.motion_blur_position -> scene.render.motion_blur_position
    • scene.eevee.use_motion_blur -> scene.render.user_motion_blur
    • scene.eevee.motion_blur_position -> scene.render.motion_blur_position
    • scene.eevee.motion_blur_shutter -> scene.render.motion_blur_shutter
  • Light cast shadow setting have been de-duplicated between Cycles and EEVEE and moved to bpy.types.Light. (1036d9bdb2)
    • light.cycles.cast_shadow -> light.use_shadow
  • Bloom has been deprecated in EEVEE. (#123059)
    • view_layer.eevee.use_pass_bloom
    • scene.eevee.use_bloom
    • scene.eevee.bloom_threshold
    • scene.eevee.bloom_color
    • scene.eevee.bloom_knee
    • scene.eevee.bloom_radius
    • scene.eevee.bloom_clamp
    • scene.eevee.bloom_intensity
  • EEVEE (pre 4.2) specific Material settings have been deprecated or aliased where possible. (c7807a425a)
    • bpy.types.Material.blend_method => bpy.types.Material.surface_render_method. 'Opaque' and 'Alpha Clip' maps to deferred.
    • show_transparent_back has been renamed to use_transparency_overlap.
    • use_screen_refraction has been renamed to use_raytrace_refraction.
    • use_sss_translucency and use_sss_translucency have been deprecated.
  • Light probe API has been changed. (6a71a91b83)
    • Each light probe type now has its own type ()
    • grid_ prefix has been removed and access has been limited to volume probes.
    • Parallax and other sphere probe only properties are be limited to sphere probes.
    • visibility properties have been deprecated.
  • Deprecated shadow settings
    • shadow_cube_size and shadow_cascade_size are not used anymore and will be removed in a future release.

Nodes

  • Unused parent argument removed from the NodeTreeInterface.new_panel function for creating node group panels. (#118792)
  • Some node properties have been renamed to fix name collisions (deb332601c):
    • Compositor Box/Ellipse Mask node: width -> mask_width (same for height)
    • Shader AOV Output node: name -> aov_name
    • Geometry Color node: color -> value

Image Object Operators

  • The "add image object" operator has been deduplicated and unified into one operator: object.empty_image_add. (013cd3d1ba)
    Previously there were two operators to add image empties (object.load_reference_image and object.load_background_image) with a separate operator for dropping (object.drop_named_image).
  • The "add/remove background image from camera" operator has been renamed to clarify that this is only for the camera object (013cd3d1ba):
    • view3d.background_image_add -> view3d.camera_background_image_add.
    • view3d.background_image_remove -> view3d.camera_background_image_remove.