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In an Augmented Reality scene, users looks at the live camera feed. Virtual objects anchor at specific positions of the real world. Our task is to let the user place virtual in the real world. To achieve that, the user simply taps on the smartphone screen. Through a hit test, our script then creates an anchor in the real world and links that to a virtual 3D model entity.

That’s the high level overview. To code this anchoring logic, a few intermediate steps are needed:

1. Hit Test: converts coordinates of the user’s screen tap and sends the normalized coordinates to the AR system. This checks what’s in the real world at that position.
2. Register Anchor: next, our script instructs the AR system to create an anchor at that position.
3. Link Anchor: finally, the ID of the created anchor is linked to our entity. This allows Sumerian to continually update the transform of our 3D entity. Thus, the object stays in place in the real world, even when the user moves around.

Transforming these steps into code, this is what our code architecture looks like. It includes three call-backs, starting with the touch event and ending with the registered and linked AR anchor.

The WebXR standard isn’t finished yet. How does the web-based Amazon Sumerian platform integrate with the real world for Augmented Reality? We’ll take a look at the glue that binds the 3D WebGL contents from the web view to the native AR platform (ARCore / ARKit). To access this, we will also look at Sumerian internal engine classes like ArAnchorComponent, which handle the cross-platform web-to-native mapping.

This article continues from part 1, which covered the scripting basics of Amazon Sumerian and prepared the scene for AR placement.

Anchors in Amazon Sumerian

Let’s start with a bit of background of how Sumerian handles AR.

Ultimately, a 3D model is placed in the user’s real environment using an “Anchor”. This is directly represented in Sumerian. To create an anchor in your scene, your code goes through the following steps:

How to (re)-position the virtual objects in the real world in an Augmented Reality experience – while still having an interactive scene? Elegantly guide your users through the placement process.

The official AR tutorial from Amazon contains a simple script: by tapping anywhere in the scene, it instantly moves the objects to that position. However, for the Digital Healthcare Explained app, I needed a more flexible behavior:

1. Activate placement mode by tapping on a specific object in the 3D scene. In this case, I decided that tapping the host avatar triggers placement mode.
2. The host then explains what to do: tapping on another surface moves the host and related objects. Guide users through the process. The Sumerian hosts are ideal to explain the process.
3. The user taps on a real-world surface in the AR scene.
4. Next, the scene contents move, the anchor updates and the host confirms.

New ES6 Based Scripting

Additionally, Amazon Sumerian is evolving its scripting language. A major upgrade to ES6 is underway. It’s fully based on classes and fits better into the actions and state machines used in other places of Sumerian. The new APIs are still marked as “Preview”. However, the old APIs are already called “Legacy” or “Old Script Format”.

While documentation for the new Sumerian Engine APIs directly is already available, it’s very brief and doesn’t contain many examples. The official tutorials are still based on the legacy API.

I decided to re-write the script using the new APIs. It involves calling a lot of internal parts of Sumerian. Thus, it’s a lot more complex than all other examples for the new API currently out there. However, it’s interesting to dig more into the internals of how a modern, web-based AR environment works.

Amazon Sumerian is a purely cloud-based tool. Its scenes are intended to be run directly from the cloud. As such, one of the most common questions is: how can I download the scene I created in Amazon Sumerian? You might want to do this to have a backup, to send it to a colleague or to move the scene to another region.

Snapshots

The easiest way to backup your scene is to create a snapshot. This is directly integrated into the main Sumerian editor UI. Select the root node of the scene in the Entities panel. Next, navigate to the “Snapshots” section in the inspector panel.

In this panel, you can create snapshots that are easy to return to later. I’d recommend creating a snapshot before major changes in your app, after finishing vital parts of code, and obviously for every publicly released version.

However, the snapshots are internal to the scene. How to get content from one scene to another?

So far, we have set up a fully functional scene for our ambitious Augmented Reality project. The overall idea: a host avatar explains different 3D objects, which are placed in the user’s surroundings. Only one piece is missing – an animation.

In this part of the article series, we’ll look at three possible ways to animate objects in Amazon Sumerian: timelines, “classic” continuous animations and tween actions as part of state machines in behaviors. All three have different advantages and use cases. Thus, it’s important that you can decide which approach is best for each situation.

This is a capture of the current prototype and what it’ll look like, captured from a phone in Augmented Reality.

Animation Actions

Let’s get started with the tween actions. In the previous parts, we’ve already integrated several state machines and actions into our scene. This approach ties in perfectly well into the same approach.

Learn how to let individual parts of your AR / VR app communicate with each other. This part of the tutorial lets the user trigger actions within your scene. For example: the host starts explaining an object when you tap on it. Internally, the connection is established via messages. It’s a vital concept to understand on your journey to real-life AR apps with Amazon Sumerian.

The guide builds upon the project created in the previous parts of the article: 1 – general setup, 2 – speech & gestures, 3 – 3D Models & AR Anchors.

App Scenario: “Digital Healthcare Explained”

After the basic components of the scene are in place, it’s time to wire everything together. We want to achieve two things:

• Chain sequences together to make one thing happen after another
  
• Let the user interact with entities in the scene
  

Our demo app informs the user about different healthcare topics. The following chart summarizes its flow:

At first, the host greets the user. Then, several 3D models representing different healthcare topics appear around the host. The user selects one of these topics by tapping the respective entity. As we’re creating an Augmented Reality app, the user can walk around in the room to discover different topics.

Once the user tapped on one of these topics, the host starts explaining. Specific animations for the selected object start, which help understanding the topic.

After the host finished the explanation, the user can select the next topic.

Messages: Communication within the Scene

Events are broadcasted through messages. These are simply user-defined strings. In Sumerian, they’re often referred to as “channels”.