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Tutorial: Adding Touch Gestures with the Patch Editor

In this tutorial, we’ll use the Patch Editor to create an effect that responds to interactions with the screen of the device - like taps and swipes.

Download the sample content to follow along. If you open the finished project, you'll see we're going to build an effect with a clown nose and confetti.

The clown nose will get bigger when you pinch the screen and the confetti will appear in response to a long press.

Opening the Patch Editor

To get started, open the unfinished version in the sample content folder.

You should see a 3D object that looks like a red nose in the Viewport and Simulator, attached to the face.

You'll should also see 3 particle systems listed in the Scene panel. They're called red emitter, yellow emitter and green emitter. Together, they create the confetti effect:



To start working with patches, open the Patch Editor:

  1. Click View.
  2. Select Show/Hide Patch Editor.

There's already a simple patch graph in the Patch Editor:



The graph uses a face landmark patch, Nose, to fix the clown nose to the tip of the nose.

Using the Screen Pinch patch

First you're going to add the interaction that changes the size of the clown nose. You'll use the Screen Pinch patch to do this - but there are all kinds of interaction patches to choose from.

Start by adding the patch that will detect a pinching movement on the device screen:

  1. Double-click anywhere in the Patch Editor.
  2. Select a Screen Pinch patch from the menu.
  3. Click Insert Patch.

You'll see the new patch in the Patch Editor:



The Screen Pinch patch has four ports. We're only going to use the Scale output port, because we want to use this interaction to control the size of the clown nose.

To control all of the scale coordinates of the clown nose at once, you'll need to take the screen pinch gesture and convert it into one point. To do this you can use the Pack patch.

To add the patch:

  1. Double-click in the Patch Editor.
  2. Insert the Pack patch.

Then, connect the Scale port in the Screen Pinch patch to each of the 3 input ports in the Pack patch:



Now you've converted the screen pinch gesture into one point, you can connect it to a patch representing the scale of the clown nose itself. To do this:

  1. Go to the Scene panel and select clown_nose.dae.
  2. Find the Scale property in the Inspector.
  3. Click the small arrow next to Scale.
  4. Connect the output port of the Point patch to the 3D Scale input in the patch you just created.


The scale of the clown nose should now change when you pinch the screen - use the Spark AR Player app to try it out.

Using the Screen Long Press patch

As you can see in the Viewport and the Simulator, the confetti is visible all the time. Let’s change this using the **Screen Long Press*** patch.

First create the patch:

  1. Double-click anywhere in the Patch Editor.
  2. Find the Screen Long Press patch, and insert it.

This patch has three ports. We're going to focus on the State port:



It outputs a boolean data type, which means at any point in time it's either true or false. In this graph, it means means the long press gesture is either detected or it isn't.

To tell Spark AR Studio what to do when a long press is detected, you'll need to:

  1. Insert an If Then Else patch, using the menu in the Patch Editor.
  2. Connect the State port in the Screen Long Press patch to the Condition port in the If Then Else patch.
  3. Change the 0 value next to the Then port in the If Then Else patch to 10. This will set how long the press needs to be for the confetti to be triggered.


Next, you'll need to send this signal to the particle systems. The property that controls the rate at which particles are emitted is the Birthrate, so that's where you need to send the signal.

To send the signal to the particle system:

  1. Go to the Scene panel and select the each particle system - you can select them all at the same time by holding down command or control on your keyboard.
  2. Click the arrow next to Birthrate to insert this patch into the Patch Editor.

You’ll see 3 patches, representing the Birthrate of each particle system.

Connect the output port on the right hand side of the If Then Else patch to the Birthrate ports in each patch:



The confetti in your scene should now only appear when a long press is detected.

To test this, click the hamburger menu at the top of the Simulator, and select Simulate Touch:

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