Custom Nodes

Custom Nodes

What are Custom Nodes?

Custom nodes allow you to extend GM_Visual with your own Python code. Unlike built-in nodes (which are part of the repository), custom nodes live in a dedicated folder in your user profile. This means:

• No need to modify the GM_Visual source code
• Your nodes persist across updates
• You can share node files with other users simply by copying .py files

Custom Nodes Folder

The default custom nodes directory is created automatically at installation time:

%APPDATA%\GM_Visual\custom_nodes\

On a typical Windows installation this expands to:

C:\Users\<your_username>\AppData\Roaming\GM_Visual\custom_nodes\

Folder Structure

Custom nodes are organised the same way as built-in nodes: a subcategory folder inside the root custom nodes directory, containing one .py file per node:

custom_nodes\
├── demo\
│   ├── __init__.py
│   └── hello_custom_node.py   ← demo node (auto-generated)
├── my_category\
│   ├── __init__.py
│   ├── my_first_node.py
│   └── my_second_node.py
└── __init__.py

Each subfolder of custom_nodes\ becomes a subcategory visible in the Custom nodes section of the Node Library panel.

Finding Custom Nodes in the Node Library

1. Open GM_Visual and look at the Node Library tab in the right panel.
2. In the Category dropdown, select Custom nodes.
3. The subcategories that correspond to your subfolders appear below.
4. Expand a subcategory to see the available nodes.
5. Drag a node button onto the canvas — or double-click it — to add it.

Creating a Custom Node

Each node file must follow this template. The file name becomes the node identifier.

Minimum template

"""
MyNode - short description.
"""
from core import NodeBase, PinType


class MyNode(NodeBase):
    """One-line description."""

    def __init__(self, node_id: str):
        super().__init__(
            node_type="MyNode",
            name="My Node",
            description="What this node does.",
            version="1.0.0",
            author="Your Name",
            category_tags=["custom"]
        )
        self.node_id = node_id
        self._initialize_pins()

    def _initialize_pins(self) -> None:
        self.add_input_pin("value_in", PinType.FLOAT, description="Input value")
        self.add_output_pin("value_out", PinType.FLOAT, description="Output value")

    def _execute_impl(self) -> None:
        val = self.get_input_value("value_in", default=0.0)
        self.set_output_value("value_out", val * 2.0)

    def get_display_text(self) -> str:
        return "My\nNode"


def create_my_node_node(node_id: str) -> MyNode:
    """Factory function - REQUIRED. Name must be: create_{file_name}_node"""
    return MyNode(node_id=node_id)

Key rules

• File name: use snake_case, e.g. my_node.py. This becomes the node identifier used internally.
• Factory function: must be named create_{file_name}_node. For my_node.py the function is create_my_node_node.
• Class: must inherit from NodeBase (imported from core).
• Pins: declare all input and output pins inside _initialize_pins().
• Execution logic: write computation inside _execute_impl().

Available Pin Types

Import PinType from core and use the following constants (defined in src/core/pin_system.py):

Basic types

Constant	Value string	Description
PinType.INTEGER	"int"	Integer number
PinType.FLOAT	"float"	Floating-point number
PinType.STRING	"str"	Text string
PinType.BOOLEAN	"bool"	Boolean (True / False)
PinType.ANY	"any"	Accepts any data type
PinType.NONE	"none"	No data — trigger / event pin only

Container types

Constant	Value string	Description
PinType.LIST	"list"	Generic Python list
PinType.DICT	"dict"	Generic Python dictionary
PinType.LIST_OF_FLOATS	"list_of_floats"	List of float values
PinType.LIST_OF_INTS	"list_of_ints"	List of integer values
PinType.LIST_OF_STRINGS	"list_of_strings"	List of strings
PinType.LIST_MIXED	"list_mixed"	List of mixed types

Signal / domain types

Constant	Value string	Description
PinType.DFTM	"dftm"	DataFrame Time — time-series signal (GM_modules.Signals)
PinType.DFTB	"dftb"	DataFrame Table — tabular signal data (GM_modules.Signals)
PinType.MATERIAL	"material"	Material object (GM_modules.Materials)

Ansys DPF types

Constant	Description
PinType.ANSYS_DPF_MODEL	Ansys DPF Model object
PinType.ANSYS_DPF_MESHED_REGION	Ansys DPF Meshed Region object
PinType.ANSYS_DPF_FIELDS_CONTAINER	Ansys DPF Fields Container object
PinType.ANSYS_DPF_TIME_SCOPING	Ansys DPF Time Scoping object
PinType.ANSYS_DPF_SCOPING	Ansys DPF Mesh Scoping object

Demo Node

A demo node is automatically generated at:

%APPDATA%\GM_Visual\custom_nodes\demo\hello_custom_node.py

This node outputs the constant string "Hello from Custom Node!" and serves as a working example you can copy and modify.

Troubleshooting

My node does not appear in the library

• Make sure the file is inside a subcategory folder (not directly in custom_nodes\).
• The file name must end in .py and must not start with __ or end with _gui.py.
• Re-select the Custom nodes category in the dropdown to refresh the list.

Error when dropping the node on canvas

• Check that the factory function is correctly named: create_{file_name}_node.
• Make sure the class inherits from NodeBase and core is importable (GM_Visual must be running from the correct environment).
• Look at the terminal / console output for the full Python traceback.

custom_nodes folder is missing

Run the repair command from the GM_Visual directory:

python install.py repair