TouchDesigner Tutorial: Basics of Instancing

This tutorial covers the fundamental principles and concepts of instancing in TouchDesigner, demonstrating how to efficiently render multiple copies of geometry using GPU-based techniques.

What is Instancing?

Instances are copies of geometry that are handled exclusively on the GPU. This makes instancing a far more efficient way to draw and manipulate many copies of a piece of geometry compared to traditional methods. Instead of creating separate geometry components for each copy, instancing allows you to define one piece of geometry and control multiple copies through channel data.

Setting Up Basic Instancing

Step 1: Create the Geometry

Start by adding a Box SOP to your network and connecting it to a Geometry component. This will be the base geometry that gets instanced.

Step 2: Enable Instancing

Navigate to the Instance page of your Geometry component and turn on instancing. You’ll need to specify an operator (OP) that serves as the source of data describing your instance positions.

Step 3: Set Up the Instance Data Source

Create a Constant CHOP connected to a Null CHOP. Set this Null as your default instance OP. The Constant CHOP will hold the channel data that controls your instances.

Controlling Instance Attributes

Translation (Position)

Add three channels to your Constant CHOP:

• TX - X position
• TY - Y position
• TZ - Z position

On the Geometry component’s Instance page, set the Translate X, Y, and Z parameters to pull from these respective channels. Each sample in your channels represents a different instance.

Creating Multiple Instances

Use a Join CHOP to merge multiple Constant CHOPs together. The Join CHOP places samples in sequence, so each sample describes a separate instance. For example:

• First Constant: TX = -2 (instance on the left)
• Second Constant: TX = 2 (instance on the right)
• Third Constant: TX = 0 (instance in the center)

Rotation

Add rotation channels to control instance orientation:

• RX - Rotation around X axis
• RY - Rotation around Y axis
• RZ - Rotation around Z axis

Update the Geometry component’s Instance page to pull rotation data from these channels.

Scale

Add scale channels for size control:

• SX - Scale in X dimension
• SY - Scale in Y dimension
• SZ - Scale in Z dimension

Set default values to 1 for uniform scaling, then adjust per instance as needed.

Color

On the Instance 2 page of the Geometry component, you’ll find color parameters. Add color channels:

• R - Red channel
• G - Green channel
• B - Blue channel

Map these to the corresponding color parameters to give each instance a unique color.

Key Concepts

Sample-Based Instance Control

Every sample inside your channels describes another instance. This is the fundamental concept that makes instancing powerful - you can control hundreds or thousands of instances simply by adding more samples to your channel data.

GPU Efficiency

Because instances are handled entirely on the GPU, this approach is significantly more efficient than creating separate geometry components. This is crucial for real-time performance when working with large numbers of objects.

Flexible Data Sources

While this tutorial uses a single default instance OP for all attributes, you can actually pull data from separate operators for different attributes:

• One OP for translation data
• Another OP for rotation data
• Another OP for scale data
• And so on for Instance 2 page attributes

Practical Tips

1. Use Null CHOPs - Always connect your data through a Null CHOP before referencing it in the Geometry component. This provides a clean reference point.

2. Snapshot Channels - When adding new channels to existing Constant CHOPs, use the snapshot feature to capture all channels and update values efficiently.

3. Match Channel Names - Ensure your channel names (TX, TY, TZ, etc.) match what you reference in the Geometry component’s Instance parameters.

4. Start Simple - Begin with position control, then add rotation, scale, and color as needed.

Summary

Instancing in TouchDesigner provides a GPU-optimized way to render multiple copies of geometry with individual control over position, rotation, scale, and color. By using CHOP data to drive instance attributes, you can create complex animations and visualizations that would be impossible with traditional geometry duplication methods.

This tutorial covers the foundational concepts - there’s much more you can do with instancing, including using different data sources for different attributes and creating procedural animations through CHOP networks.