NodeModel Case Study - Custom UI

NodeModel based nodes provides significantly more flexibility and power than the Zero-Touch nodes. In this example, we will take the Zero-Touch grid node to the next level by adding an integrated slider that randomizes the rectangle size.

The slider scales the cells relative to their size so the user doesn't have to provide a slider with the correct range.

The Model-View-Viewmodel Pattern

Dynamo is based on the model-view-viewmodel (MVVM) software architecture pattern to keep the UI separate from the back-end. When creating ZeroTouch nodes, Dynamo does the data bind between a node's data and its UI . To create a custom UI, we have to add the data-binding logic.

At a high-level there are two parts to establishing a model-view relationship in Dynamo:

  • A NodeModel class to establish the core logic of the node (the "model")
  • A INodeViewCustomization class to customize how the NodeModel is being viewed (the "view")

NodeModel objects already have an associated view-model (NodeViewModel), so we can just focus on the model and view for custom UI.

How To Implement NodeModel

NodeModel nodes have several significant differences from Zero-Touch nodes that we will cover in this example. Before we jump into UI customization, let's start by building out the NodeModel logic.

1. Create project structure:

A NodeModel node can only call functions, so we need to separate the NodeModel and functions into different libraries. The standard way of doing this for Dynamo packages is creating separate projects for each. Start by creating a new Solution to encompass the projects.

  1. Select File > New > Project
  2. Select Other Project Types to bring up the Solution option
  3. Select Blank Solution
  4. Name the solution CustomNodeModel
  5. Select Ok

Create two C# class library projects in the solution: one for functions and one to implement the NodeModel interface.

  1. Right-click on the Solution and select Add > New Project
  2. Choose Class Library
  3. Name it CustomNodeModel
  4. Click Ok
  5. Repeat the process to add another project named CustomNodeModelFunctions

Next, we need to rename the class libraries that were automatically created and add one to the CustomNodeModel project. The class GridNodeModel implements the abstract NodeModel class, GridNodeView is used to customize the view, and GridFunction contains any functions we need to call.

  1. Add another class by right-clicking on the CustomNodeModel project, selecting Add > New Item... and choose Class.
  2. In the CustomNodeModel project, we need GridNodeModel.cs and GridNodeView.cs class
  3. In the CustomNodeModelFunction project, we need a GridFunctions.cs class

Before we add any code to the classes, add the necessary packages for this project. CustomNodeModel will need ZeroTouchLibrary and WpfUILibrary, and CustomNodeModelFunction will only need ZeroTouchLibrary. The WpfUILibrary will be used in the UI customization we do later on, and ZeroTouchLibrary will be used for creating geometry. Packages can be added individually for projects. Since these packages have dependencies, Core and DynamoServices will be automatically installed.

  1. Right-click on a project and select Manage NuGet Packages
  2. Install only the required packages for that project

Visual Studio will copy the NuGet packages we referenced to the build directory. This can be set to false so we don't have any unnecessary files in the package.

  1. Select Dynamo NuGet Packages
  2. Set Copy Local to false

2. Inherit the NodeModel class

As mentioned previously, the primary aspect that makes a NodeModel node different from a ZeroTouch node is its implementation of the NodeModel class. A NodeModel node needs several functions from this class, and we can get them by adding :NodeModel after the class name.

Copy the following code into the GridNodeModel.cs.

using System;
using System.Collections.Generic;
using Dynamo.Graph.Nodes;
using CustomNodeModel.CustomNodeModelFunction;
using ProtoCore.AST.AssociativeAST;
using Autodesk.DesignScript.Geometry;

namespace CustomNodeModel.CustomNodeModel
    [NodeDescription("An example NodeModel node that creates a rectangular grid. The slider randomly scales the cells.")]
    [InPortNames("xCount", "yCount")]
    [InPortTypes("double", "double")]
    [InPortDescriptions("Number of cells in the X direction", "Number of cells in the Y direction")]
    [OutPortDescriptions("A list of rectangles")]
    public class GridNodeModel : NodeModel
        private double _sliderValue;
        public double SliderValue
            get { return _sliderValue; }
                _sliderValue = value;
        public GridNodeModel()
        public override IEnumerable<AssociativeNode> BuildOutputAst(List<AssociativeNode> inputAstNodes)
            if (!HasConnectedInput(0) || !HasConnectedInput(1))
                return new[] { AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), AstFactory.BuildNullNode()) };
            var sliderValue = AstFactory.BuildDoubleNode(SliderValue);
            var functionCall =
                new Func<int, int, double, List<Rectangle>>(GridFunction.RectangularGrid),
                new List<AssociativeNode> { inputAstNodes[0], inputAstNodes[1], sliderValue });

            return new[] { AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), functionCall) };

This different from Zero-Touch nodes. Let's understand what each part is doing.

  • Specify the Node attributes like Name, Category, InPort/OutPort names, InPort/OutPort types, descriptions.

  • public class GridNodeModel : NodeModel is a class that inherits the NodeModel class from Dynamo.Graph.Nodes.

  • public GridNodeModel() { RegisterAllPorts(); } is a constructor that registers the node inputs and outputs.

  • BuildOutputAst() returns an AST (Abstract Syntax Tree), the required structure for returning data from a NodeModel node.

  • AstFactory.BuildFunctionCall() calls the RectangularGrid function from GridFunctions.cs.

  • new Func<int, int, double, List<Rectangle>>(GridFunction.RectangularGrid) specifies the function and its parameters .

  • new List<AssociativeNode> { inputAstNodes[0], inputAstNodes[1], sliderValue }); maps the node inputs to function parameters

  • AstFactory.BuildNullNode() builds a null node if the input ports are not connected. This is to avoid displaying a warning on the node.

  • RaisePropertyChanged("SliderValue")Notifies the UI when the slider value changes

  • var sliderValue = AstFactory.BuildDoubleNode(SliderValue)Build a node in the AST that represents the slider value

  • Change an input to the sliderValue variable in the functionCall variable new List<AssociativeNode> { inputAstNodes[0], sliderValue });

3. Call a function

The CustomNodeModelFunction project will be built into a separate assembly from CustomNodeModel so that it can be called.

Copy the following code into GridFunction.cs.

using Autodesk.DesignScript.Geometry;
using Autodesk.DesignScript.Runtime;
using System;
using System.Collections.Generic;

namespace CustomNodeModel.CustomNodeModelFunction
    public class GridFunction
        public static List<Rectangle> RectangularGrid(int xCount = 10, int yCount = 10, double rand = 1)
            double x = 0;
            double y = 0;

            Point pt = null;
            Vector vec = null;
            Plane bP = null;

            Random rnd = new Random(2);

            var pList = new List<Rectangle>();
            for (int i = 0; i < xCount; i++)
                x = 0;
                for (int j = 0; j < yCount; j++)
                    double rNum = rnd.NextDouble();
                    double scale = rNum * (1 - rand) + rand;
                    pt = Point.ByCoordinates(x, y);
                    vec = Vector.ZAxis();
                    bP = Plane.ByOriginNormal(pt, vec);
                    Rectangle rect = Rectangle.ByWidthLength(bP, scale, scale);
            return pList;

This function class is very similar to the Zero-Touch Grid case study with one difference:

  • [IsVisibleInDynamoLibrary(false)] prevents Dynamo from "seeing" the following method and class since the function is already being called from CustomNodeModel.

Just as we added references for NuGet packages, CustomNodeModel will need to reference CustomNodeModelFunction to call the function.

The using statement for CustomNodeModel will be inactive until we reference the function

  1. Right-click on CustomNodeModel and select Add > Reference
  2. Choose Projects > Solution
  3. Check CustomNodeModelFunction
  4. Click Ok

4. Customize the view

To create a slider, we need to customize the UI by implementing the INodeViewCustomization interface.

Copy the following code into GridNodeView.cs

using Dynamo.Controls;
using Dynamo.Wpf;

namespace CustomNodeModel.CustomNodeModel
    public class CustomNodeModelView : INodeViewCustomization<GridNodeModel>
        public void CustomizeView(GridNodeModel model, NodeView nodeView)
            var slider = new Slider();
            slider.DataContext = model;

        public void Dispose()
  • public class CustomNodeModelView : INodeViewCustomization<GridNodeModel> defines the necessary functions to customize the UI.

After the structure of the project is set up, use Visual Studio's design environment to build a user control and define its parameters in an .xaml file. From the tool box, add a slider to <Grid>...</Grid>.

  1. Right click on CustomNodeModel and select Add > New Item
  2. Select WPF
  3. Name the user control Slider
  4. Click Add

Copy the following code into Slider.xaml

<UserControl x:Class="CustomNodeModel.CustomNodeModel.Slider"
             d:DesignHeight="75" d:DesignWidth="100">
    <Grid Margin="10">
        <Slider Grid.Row="0" Width="80" Minimum="0" Maximum="1" IsSnapToTickEnabled="True" TickFrequency="0.01" Value="{Binding SliderValue}"/>
  • The parameters of the slider control is defined in In the .xaml file. Minimum and Maximum attributes defines the the numerical range of this slider.

  • Inside <Grid>...</Grid> we can place different user controls from the Visual Studio Toolbox

When we created the Slider.xaml file, Visual Studio automatically created a C# file called Slider.xaml.cs that initializes the slider. Change the namespace in this file.

using System.Windows.Controls;

namespace CustomNodeModel.CustomNodeModel
    /// <summary>
    /// Interaction logic for Slider.xaml
    /// </summary>
    public partial class Slider : UserControl
        public Slider()
  • The namespace should be CustomNodeModel.CustomNodeModel

The GridNodeModel.cs, defines the slider computation logic.

5. Configure as a package

Before we build the project, the final step is to add a pkg.json file so that Dynamo can read the package.

  1. Right-click on CustomNodeModel and select Add > New Item
  2. Select Web
  3. Select JSON File
  4. Name the file pkg.json
  5. Click Add
  • Copy the following code into pkg.json
  "license": "MIT",
  "file_hash": null,
  "name": "CustomNodeModel",
  "version": "1.0.0",
  "description": "Sample node",
  "group": "CustomNodes",
  "keywords": [ "grid", "random" ],
  "dependencies": [],
  "contents": "Sample node",
  "engine_version": "1.3.0",
  "engine": "dynamo",
  "engine_metadata": "",
  "site_url": "",
  "repository_url": "",
  "contains_binaries": true,
  "node_libraries": [
    "CustomNodeModel, Version=1.0.0, Culture=neutral, PublicKeyToken=null",
    "CustomNodeModelFunction, Version=1.0.0, Culture=neutral, PublicKeyToken=null"
  • "name": determines the name of the package and its group in the Dynamo Library

  • "keywords": provide search terms for searching the Dynamo Library

  • "node_libraries": [] the libraries associated with the package

    The last step is to build the solution and publish as a Dynamo package. Please see the Package Deployment chapter for how to create a local package before publishing online and how to build a package right out of Visual Studio.

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