Python API & Text Editor

Custom Script Directories

Multiple script directory paths can now be configured in the Preferences (File Paths section). Each of these directories supports the regular script directory layout with a startup file (or files?), add-ons, modules and presets. (ba25023d22)

Compatibility notes:

• bpy.types.PreferencesFilePaths.script_directory is deprecated. The directories are exposed in bpy.types.script_directories now.
• bpy.utils.script_path_pref is removed, use bpy.utils.script_paths_pref instead.

Blender Handlers

• Added bpy.app.handlers (save_post_fail, load_post_fail), so the *_pre handles will always call a *_post handler, even on failure (46be42f6b1).
• File load handlers (save_{pre/post/post_fail}, load_{pre/post/post_fail}) now accept a filepath argument so the file being loaded or saved is known (46be42f6b1)

Internal Mesh Format

The mesh data structure refactoring from earlier releases has continued in 3.6. See the similar sections in the 3.4 and 3.5 release notes.

• The vertex and edge indices stored for mesh face corners (MeshLoop/MLoop) are now stored as separate attributes, named .corner_vert and .corner_edge (16fbadde36).
• Mesh faces (polygons) are now stored with a single integer internally, rather than the MPoly type.
  • This means that the order of faces is always consistent with the order of face corners (loops).
  • The MeshPolygon.loop_total property is no longer editable. Instead the size of each face should be changed with the next face's loop_start property.
• Mesh edges are now stored in a generic attribute named .edge_verts (2a4323c2f5).
  • A new 2D integer vector attribute type is added to store edge data (988f23cec3).
• UV seams are now stored as a generic attribute, accessible with the .uv_seam name on the edge domain (cccf91ff83).
• The smooth/sharp status for faces is now stored as a generic attribute with the sharp_face name (5876573e14).
  • In some cases, meshes are now smooth by default (when created from scratch, without from_pydata).
    • To simplify getting the previous behavior, new API functions Mesh.shade_flat() and Mesh.shade_smooth() have been added (ee352c968f).

Other Changes

• New bpy_extras.node_utils.connect_sockets() function to allow creating links between virtual sockets (grayed out sockets in Group Input and Group Output nodes) (81815681d0).
• New action_tweak_storage property in AnimData, which exposes the temporary storage used to stash the main action when tweaking an NLA clip (997ad50b49).