Creating Custom Nodes for Visual Compositor

Create the node class.

Custom node classes need to inherit from the Unity.VisualCompositor.CompositorNode base class. This class is an abstract base class, which requires a single method to be implemented:

using Unity.VisualCompositor;

public class MyCustomNode : CompositorNode {
    public override void Render() { }
}

Visual Compositor will call this method when executing its Compositor Graph asset.

UI Controls

To construct controls for the UI of the custom node, declare fields with [ExposeField] attributes.

For example:

[ExposeField] public float param;

This will create a FloatField in the node as parameters.

We can use almost any serializable type, where each will create its corresponding Unity UI.

Node Inputs/Outputs

Node Inputs

In order to get input into the custom node from the outputs of other nodes, we decorate its fields with [InputPort] special attribute. When the Render() method is called on the custom node, these fields will have values in them ready to be used.

For example:

[InputPort(name: "input")] private RenderTexture m_input;

This declares a field named m_input, which is labeled as input and able to receive a RenderTexture from another node.

There can be as many input nodes defined with any types. The Selection Group node for example, outputs a value of type HashSet<GameObject>.

Node Outputs

Visual Compositor will automatically copy the values of all output fields to any connected nodes. These output fields are fields decorated with [OutputPort] attributes and we can set their values inside the Render() method of the custom node.

For example:

[OutputPort(name: "output")] private RenderTexture m_output;

This declares an output port named m_output, which is labeled as output and able to send a RenderTexture to any connected node.

Node UI Extension

A custom node may be decorated with a [CompositorNode] attribute with the following parameters for further customization.

No	Name	Description	Required
1	title	The name used in the create node menu.	✔️
2	tooltip	The documentation string (tooltip) for the node.	✔️
3	w	The width of the node widget in the editor.
4	userCreatable	If true, allows users to create the node through the 'Create Node' menu.
5	icon	The path to a custom icon for the node.

We can also extend the UI of a custom node by writing a class inheriting from CustomCompositorNodeEditor with [CompositorNodeEditor] attribute. For example:

using Unity.VisualCompositor.Editor;

[CompositorNodeEditor(typeof(MyCustomNode))]
public class MyCustomNodeEditor : CustomCompositorNodeEditor {

    public override NodeUI CreateUI(CompositorNode compositorNode) {
        // This method is called first. If you need use the node
        // in the below method, capture it here.
        // Eg: this.node = compositorNode;
        return new NodeUI();
    }

    public override void ConfigureUI(NodeUI ui) {
        // This is called last, you can modify the default UI here.
    }
}

Complete Example

Runtime Script

using UnityEngine;
using Unity.VisualCompositor;

// Any class that inherits Compositor Node will be available to use in the Compositor.
[CompositorNode("My Custom Node", "A node.", icon: "SpeechBubble.png")]
public class MyCustomNode : CompositorNode {

    // This method implements the functionality of the node. You can read from input port fields and write to output port fields,
    // the Compositor takes care of moving those values around the graph.
    public override void Render() {
        if (null == m_input) {
            if (null != m_output) {
                ClearRenderTexture(m_output);
            }
            return;
        }

        if (null == m_output) {
            m_output           = new RenderTexture(m_input);
            m_output.hideFlags = HideFlags.DontSaveInEditor;
        }

        if(m_material == null) {
            Shader shader = Shader.Find("MyCustomNodeShader");
            m_material           = new Material(shader);
            m_material.hideFlags = HideFlags.DontSaveInEditor;
        } 

        Graphics.Blit(m_input, m_output, m_material);
    }

    private static void ClearRenderTexture(RenderTexture rt) {
        RenderTexture prevRT = RenderTexture.active;
        RenderTexture.active = rt;
        GL.Clear(true, true, Color.clear);
        RenderTexture.active = prevRT;
    }

//--------------------------------------------------------------------------------------------------------------------------------------------------------------

    // Fields that have an InputPort attribute will become input ports in the Compositor Editor. 
    [InputPort(name: "input")] private RenderTexture m_input;

    // Fields that have an OutputPort attribute will become output ports in the Compositor Editor.
    [OutputPort(name: "output")] private RenderTexture m_output;

    // Fields that have an ExposeField attribute will have the appropriate ui controls created in
    // the node editor. Any serializable field types can be used. 
    [ExposeField] public float param;

    Material m_material;
}

Shader

Shader "MyCustomNodeShader" {
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader {
        // No culling or depth
        Cull Off ZWrite Off ZTest Always

        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata{
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f{
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert(appdata v) {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;

            float4 frag(v2f i) : SV_Target {
                float4 c = tex2D(_MainTex, i.uv);
                const half t = c.r;
                c.r = c.g;
                c.g = c.b;
                c.b = t;
                return c;
            }
            ENDCG
        }


    }
}

Editor Script

using Unity.VisualCompositor;
using Unity.VisualCompositor.Editor;
using UnityEditor.UIElements;
using UnityEngine;
using UnityEngine.UIElements;

[CompositorNodeEditor(typeof(MyCustomNode))]
public class MyCustomNodeEditor : CustomCompositorNodeEditor {

    public override NodeUI CreateUI(CompositorNode compositorNode) {

        NodeUI nodeUI = new NodeUI();
        m_node = compositorNode as MyCustomNode;
        return nodeUI;
    }

    public override void ConfigureUI(NodeUI ui) {
        ui.tooltip = "Hey, this is a customised tool tip!";

        Label label = new Label("Custom Editor");
        ui.extensionContainer.Add(label);

        TextField textField = new TextField() {
            label = "Foo",
            value = "Bar",
        };
        ui.extensionContainer.Add(textField);

        ui.extensionContainer.Add(new ObjectField("HogeObj") { objectType = typeof(GameObject) });

        Button button = new Button() { text = "Increase Param", };
        button.clicked += () => { ++m_node.param; };
        ui.extensionContainer.Add(button);
    }

    private MyCustomNode m_node = null;

}