Creating Custom Nodes

This guide walks through creating a custom node for the node graph system.

Step 1: Define the Node Class

Create a header file for your node. Use DECLARE_GRAPH_NODE to set up the factory pattern.

// MyCustomNodes.h
#pragma once

#include "NodeGraph/GraphNode.h"

class MyCustomNode : public GraphNode
{
public:
    DECLARE_GRAPH_NODE(MyCustomNode, GraphNode);

    virtual void SetupPins() override;
    virtual void Evaluate() override;
    virtual const char* GetNodeTypeName() const override { return "My Custom Node"; }
    virtual const char* GetNodeCategory() const override { return "Custom"; }
    virtual glm::vec4 GetNodeColor() const override;
};

Step 2: Implement the Node

In the .cpp file, use FORCE_LINK_DEF, DEFINE_GRAPH_NODE, and implement the virtual methods.

// MyCustomNodes.cpp
#include "MyCustomNodes.h"
#include "Utilities.h"

FORCE_LINK_DEF(MyCustomNodes);
DEFINE_GRAPH_NODE(MyCustomNode);

void MyCustomNode::SetupPins()
{
    // Add input pins with default values
    AddInputPin("Value A", DatumType::Float, Datum(0.0f));
    AddInputPin("Value B", DatumType::Float, Datum(1.0f));

    // Add output pins
    AddOutputPin("Result", DatumType::Float);
}

void MyCustomNode::Evaluate()
{
    // Read input values
    float a = GetInputValue(0).GetFloat();
    float b = GetInputValue(1).GetFloat();

    // Compute and set output
    SetOutputValue(0, Datum(a * b + 0.5f));
}

glm::vec4 MyCustomNode::GetNodeColor() const
{
    return glm::vec4(0.8f, 0.4f, 0.1f, 1.0f);
}

Step 3: Register the Node with a Domain

Option A: Register with a single domain

Use REGISTER_GRAPH_NODE after DEFINE_GRAPH_NODE:

DEFINE_GRAPH_NODE(MyCustomNode);
REGISTER_GRAPH_NODE(MyCustomNode, "My Custom Node", "Custom", "Material", glm::vec4(0.8f, 0.4f, 0.1f, 1.0f));

Option B: Register with multiple domains

Use REGISTER_GRAPH_NODE_MULTI to register a node across multiple domains:

DEFINE_GRAPH_NODE(MyCustomNode);
REGISTER_GRAPH_NODE_MULTI(MyCustomNode, "My Custom Node", "Custom", glm::vec4(0.8f, 0.4f, 0.1f, 1.0f), "Material", "Shader");

Option C: Register inside a Domain class

Add the node directly in the domain's RegisterNodeTypes():

void MyDomain::RegisterNodeTypes()
{
    AddNodeType(MyCustomNode::GetStaticType(), "My Custom Node", "Custom", glm::vec4(0.8f, 0.4f, 0.1f, 1.0f));
}

Step 4: Force Linkage

Add FORCE_LINK_CALL(MyCustomNodes) to Engine.cpp's ForceLinkage() function to ensure the linker includes your node file.

Step 5: Add to Project

Add the .h and .cpp files to Engine.vcxproj and Engine.vcxproj.filters.

Available Data Types

DatumType	C++ Type	Access Method
DatumType::Float	float	GetFloat()
DatumType::Integer	int32_t	GetInteger()
DatumType::Bool	bool	GetBool()
DatumType::Vector	glm::vec3	GetVector()
DatumType::Vector2D	glm::vec2	GetVector2D()
DatumType::Color	glm::vec4	GetColor()

Pin Best Practices

• Always provide default values for input pins so the node works without connections.
• Use meaningful pin names that describe the data.
• Output-only nodes (sources) like TimeNode have no input pins.
• Input-only nodes (sinks) like output nodes have no output pins.
• Each input pin can only have one incoming link (the most recent link replaces any existing one).
• Output pins can connect to multiple input pins.