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How to make the following custom node tree be linked to objects, similarly to the way shader nodes are?

Python code from the Blender Template:

import bpy
from bpy.types import NodeTree, Node, NodeSocket

# Implementation of custom nodes from Python

# Derived from the NodeTree base type, similar to Menu, Operator, Panel, etc.
class MyCustomTree(NodeTree):
    # Description string
    '''A custom node tree type that will show up in the editor type list'''
    # Optional identifier string. If not explicitly defined, the python class name is used.
    bl_idname = 'CustomTreeType'
    # Label for nice name display
    bl_label = "Custom Node Tree"
    # Icon identifier
    bl_icon = 'NODETREE'


# Custom socket type
class MyCustomSocket(NodeSocket):
    # Description string
    '''Custom node socket type'''
    # Optional identifier string. If not explicitly defined, the python class name is used.
    bl_idname = 'CustomSocketType'
    # Label for nice name display
    bl_label = "Custom Node Socket"

    # Enum items list
    my_items = (
        ('DOWN', "Down", "Where your feet are"),
        ('UP', "Up", "Where your head should be"),
        ('LEFT', "Left", "Not right"),
        ('RIGHT', "Right", "Not left"),
    )

    my_enum_prop: bpy.props.EnumProperty(
        name="Direction",
        description="Just an example",
        items=my_items,
        default='UP',
    )

    # Optional function for drawing the socket input value
    def draw(self, context, layout, node, text):
        if self.is_output or self.is_linked:
            layout.label(text=text)
        else:
            layout.prop(self, "my_enum_prop", text=text)

    # Socket color
    def draw_color(self, context, node):
        return (1.0, 0.4, 0.216, 0.5)


# Mix-in class for all custom nodes in this tree type.
# Defines a poll function to enable instantiation.
class MyCustomTreeNode:
    @classmethod
    def poll(cls, ntree):
        return ntree.bl_idname == 'CustomTreeType'


# Derived from the Node base type.
class MyCustomNode(Node, MyCustomTreeNode):
    # === Basics ===
    # Description string
    '''A custom node'''
    # Optional identifier string. If not explicitly defined, the python class name is used.
    bl_idname = 'CustomNodeType'
    # Label for nice name display
    bl_label = "Custom Node"
    # Icon identifier
    bl_icon = 'SOUND'

    # === Custom Properties ===
    # These work just like custom properties in ID data blocks
    # Extensive information can be found under
    # http://wiki.blender.org/index.php/Doc:2.6/Manual/Extensions/Python/Properties
    my_string_prop: bpy.props.StringProperty()
    my_float_prop: bpy.props.FloatProperty(default=3.1415926)

    # === Optional Functions ===
    # Initialization function, called when a new node is created.
    # This is the most common place to create the sockets for a node, as shown below.
    # NOTE: this is not the same as the standard __init__ function in Python, which is
    #       a purely internal Python method and unknown to the node system!
    def init(self, context):
        self.inputs.new('CustomSocketType', "Hello")
        self.inputs.new('NodeSocketFloat', "World")
        self.inputs.new('NodeSocketVector', "!")

        self.outputs.new('NodeSocketColor', "How")
        self.outputs.new('NodeSocketColor', "are")
        self.outputs.new('NodeSocketFloat', "you")

    # Copy function to initialize a copied node from an existing one.
    def copy(self, node):
        print("Copying from node ", node)

    # Free function to clean up on removal.
    def free(self):
        print("Removing node ", self, ", Goodbye!")

    # Additional buttons displayed on the node.
    def draw_buttons(self, context, layout):
        layout.label(text="Node settings")
        layout.prop(self, "my_float_prop")

    # Detail buttons in the sidebar.
    # If this function is not defined, the draw_buttons function is used instead
    def draw_buttons_ext(self, context, layout):
        layout.prop(self, "my_float_prop")
        # my_string_prop button will only be visible in the sidebar
        layout.prop(self, "my_string_prop")

    # Optional: custom label
    # Explicit user label overrides this, but here we can define a label dynamically
    def draw_label(self):
        return "I am a custom node"


### Node Categories ###
# Node categories are a python system for automatically
# extending the Add menu, toolbar panels and search operator.
# For more examples see release/scripts/startup/nodeitems_builtins.py

import nodeitems_utils
from nodeitems_utils import NodeCategory, NodeItem

# our own base class with an appropriate poll function,
# so the categories only show up in our own tree type


class MyNodeCategory(NodeCategory):
    @classmethod
    def poll(cls, context):
        return context.space_data.tree_type == 'CustomTreeType'


# all categories in a list
node_categories = [
    # identifier, label, items list
    MyNodeCategory('SOMENODES', "Some Nodes", items=[
        # our basic node
        NodeItem("CustomNodeType"),
    ]),
    MyNodeCategory('OTHERNODES', "Other Nodes", items=[
        # the node item can have additional settings,
        # which are applied to new nodes
        # NOTE: settings values are stored as string expressions,
        # for this reason they should be converted to strings using repr()
        NodeItem("CustomNodeType", label="Node A", settings={
            "my_string_prop": repr("Lorem ipsum dolor sit amet"),
            "my_float_prop": repr(1.0),
        }),
        NodeItem("CustomNodeType", label="Node B", settings={
            "my_string_prop": repr("consectetur adipisicing elit"),
            "my_float_prop": repr(2.0),
        }),
    ]),
]

classes = (
    MyCustomTree,
    MyCustomSocket,
    MyCustomNode,
)


def register():
    from bpy.utils import register_class
    for cls in classes:
        register_class(cls)

    nodeitems_utils.register_node_categories('CUSTOM_NODES', node_categories)


def unregister():
    nodeitems_utils.unregister_node_categories('CUSTOM_NODES')

    from bpy.utils import unregister_class
    for cls in reversed(classes):
        unregister_class(cls)


if __name__ == "__main__":
    register()
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  • $\begingroup$ geometry nodes, compositor nodes, shader nodes? The answer is yes, but the method is fairly complex. You need to decide what you mean by "select" especially how to deal with selecting more than one object and you need to figure out how to use depsgraphs to recognize when the selection changes. $\endgroup$ May 14 at 23:32
  • $\begingroup$ @MartyFouts by select I mean just like shader nodes with a few differences. Only one custom node tree per object and each object has to have a unique node tree (so the object cannot be duplicated and the node tree shared between two objects). $\endgroup$
    – VSB
    May 14 at 23:39
  • $\begingroup$ You should just be able to link to bpy.types.Object instead of bpy.types.Scene in that case. Have you tried that? If so, what didn't work? $\endgroup$ May 15 at 0:23
  • $\begingroup$ @MartyFouts I can only use those for custom data I think. Looking through the basic custom node tree example there doesn't appear to be an option to change context from scene to object.. $\endgroup$
    – VSB
    May 15 at 0:41
  • $\begingroup$ Could you add some code to your question showing what works with scene? $\endgroup$ May 15 at 1:53

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