Using POPs to Drive Audio Reactive Visuals

We are now in the TouchDesigner POP era! Let’s dive into some new ways to apply audio reactive techniques with the new operator family.

The experimental release of the new POP operator family is a milestone in the history of TouchDesigner. It paves the way for a revolutionary change in visual generation, opening up new and exciting perspectives.

To fully understand what POP operators are I suggest you to watch this tutorial:

In this article, we want to take advantage of POPs to drive audio reactive visuals. So let’s go!

TouchDesigner POPs: a simple workflow

The patch starting point is a Point Generator POP that, as the name suggests, generates points in a wide series of shapes. We select a Circle shape with 10,000 points distributed on a Surface. Next we connect an Attribute POP, that allows us to manipulate the attributes associated with the input geometry. We select the color attribute and define our color, in this case a nice green one. The Random POP allows us to randomly set the incoming points geometry. We select the Inside Sphere parameter and map the color. To do this, we select the color element in the Map tab, select the Exponent parameter and multiply the operation.

The second layer of the patch starts from the same Point Generator POP we already used. We connect it to a Noise POP and then to a Trail POP. The next step is a Random POP, where we set Age as Combine Attribute Scope parameter and set Color as Output Attribute Scope.

For the third layer, we use a Grid POP that will act as the background visual. We set columns and rows and scale to fill the screen. The Grid POP goes into an Attribute POP, when we set the color attribute that is further manipulated inside a Random operator. We then apply a Noise POP and set some transform and rerange operations.

The three layers are merged into a Merge POP and from here the workflow is straightforward. We connect the Merge POP to a Geometry COMP, create Camera and Lights operators, render it all with the Render TOP and straight to a Null TOP.

The audio reactive workflow

Adding audio reactivity in TouchDesigner means adding life to our visuals. There are so many ways and techniques out there to create stunning audiovisual experiences that catch the eye.

Thanks to data manipulations via CHOPs, we can perform several techniques, from the basics to the very advanced ones. Let’s see an example.

First of all, we need to create an Audio File In CHOP and an Audio Device Out CHOP. Then we connect the Audio File In CHOP to three Audio Band EQ CHOPs, that will be in charge to filter the low, mid and high frequencies. The three audio signals are then fed into Envelope and Resample operators for further sculpting the signal. The next steps involve applying some basic maths and filtering and merging the three frequencies.

So we have our three main frequencies and we can use them to manipulate POPs parameters.

What about further adding a kick and snare detection system to create some nice pulse effect? Let’s see how.

The workflow is the same both for the kick and snare. The signal is fed into a line that comprise a Math CHOP, an Audio Spectrum CHOP and a Trim CHOP. Then we analyze the signal and find the average, apply a trail, multiply the signal, apply a threshold and finally trigger it. That’s it! We can set the threshold of both the kick and snare signals to precisely detect the transient.

Wrap Up

By combining the power of audio reactivity with the power of the new POP operators family, new perspectives arise. Thanks to POPs, we are just at the beginning of a new journey that will change the way we approach visuals in TouchDesigner.  

Regarding audio reactivity, there are several ways we can perform audio analysis. For example, we could split the signal into more than just three frequencies, thus creating a wide palette of sonic explorations. As usual, the sky is the limit.

Download the patch