HairEditorService

Overview

This service is experimental and only relevant when working with the hair/fur editor. It is unlikely you would use it from anywhere else in the code.

HairEditorService provides utility functions for the MPFB hair editor system. It manages the discovery of hair and fur asset blend files, checks whether these assets are installed, and provides methods for manipulating shader node links within hair materials.

Hair and fur assets are distributed as .blend files located in a haireditor subdirectory under the hair data folder. The service searches for these files first in the user data directory and then falls back to the system (built-in) data directory. The shader manipulation methods operate on Principled BSDF nodes inside a "Hair shader EEVEE" node group, allowing texture nodes to be temporarily connected to or disconnected from the shader's base color inputs while preserving the original link state for later restoration.

All methods are static; the class should never be instantiated.

Source

src/mpfb/services/haireditorservices.py

Dependencies

Dependency	Usage
LogService	Logging via LogService.get_logger("services.haireditorservice")
LocationService	Resolving user data and system data paths for hair blend files

Public API

Asset Paths

get_hair_blend_path()

Get the absolute path to the hair blend file. Checks the user data directory first (<user_data>/hair/haireditor/hair.blend), then falls back to the system data directory.

Returns: str or None — The absolute path to the hair blend file, or None if not found.

---

get_fur_blend_path()

Get the absolute path to the fur blend file. Checks the user data directory first (<user_data>/hair/haireditor/fur.blend), then falls back to the system data directory.

Returns: str or None — The absolute path to the fur blend file, or None if not found.

---

Asset Installation

is_hair_asset_installed()

Check whether the hair blend file exists in any of the searched locations.

Returns: bool — True if the hair blend file is found.

---

is_fur_asset_installed()

Check whether the fur blend file exists in any of the searched locations.

Returns: bool — True if the fur blend file is found.

---

Shader Links

join_texture_node_to_shader(img_node, shader_nodes, group_node, links, storage_key, store_links)

Connect a texture image node to the base color input of one or more Principled BSDF shader nodes inside the "Hair shader EEVEE" node group. Before connecting the new links, any existing links to the base color inputs are removed. If store_links is True, the previous link state is serialized as JSON and stored as a custom property on the group node so it can be restored later.

Argument	Type	Default	Description
img_node	bpy.types.ShaderNode	—	The image texture node to connect; pass None to only disconnect existing links
shader_nodes	list[bpy.types.ShaderNode]	—	List of Principled BSDF nodes to connect to
group_node	bpy.types.ShaderNodeGroup	—	The Hair shader group node, used to store link state
links	bpy.types.NodeLinks	—	The node tree's links collection
storage_key	str	—	Custom property key name for storing the previous link state
store_links	bool	—	Whether to save the previous links for later restoration

Returns: None

---

restore_shader_links(img_node, shader_nodes, group_node, nodes, links, storage_key)

Restore the original color links to Principled BSDF shaders inside the "Hair shader EEVEE" node group after a texture override has been turned off. Removes any links from the specified image node, then re-creates the original links from the saved state stored by join_texture_node_to_shader. The saved state is deleted from the group node after restoration.

Argument	Type	Default	Description
img_node	bpy.types.ShaderNode	—	The image texture node to disconnect; pass None to skip disconnection
shader_nodes	list[bpy.types.ShaderNode]	—	List of Principled BSDF nodes whose inputs to restore
group_node	bpy.types.ShaderNodeGroup	—	The Hair shader group node with saved link state
nodes	bpy.types.Nodes	—	The node tree's nodes collection, used to look up source nodes by name
links	bpy.types.NodeLinks	—	The node tree's links collection
storage_key	str	—	Custom property key name where the link state was stored

Returns: None

---

Examples

Checking for Hair Assets

from mpfb.services.haireditorservices import HairEditorService

# Check availability before attempting to use hair assets
if HairEditorService.is_hair_asset_installed():
    hair_path = HairEditorService.get_hair_blend_path()
    print(f"Hair blend file: {hair_path}")

if HairEditorService.is_fur_asset_installed():
    fur_path = HairEditorService.get_fur_blend_path()
    print(f"Fur blend file: {fur_path}")

Connecting a Texture to Hair Shaders

from mpfb.services.haireditorservices import HairEditorService

# Inside a "Hair shader EEVEE" node group:
# Connect an image texture to the principled shader base color inputs
HairEditorService.join_texture_node_to_shader(
    img_node=texture_node,
    shader_nodes=principled_nodes,
    group_node=hair_group_node,
    links=node_tree.links,
    storage_key="prev_color_links",
    store_links=True
)

# Later, restore the original shader links
HairEditorService.restore_shader_links(
    img_node=texture_node,
    shader_nodes=principled_nodes,
    group_node=hair_group_node,
    nodes=node_tree.nodes,
    links=node_tree.links,
    storage_key="prev_color_links"
)