It might be overwhelming to choose the best way to access a web service from your Android app. Maybe all you want is to parse JSON from a web service and show it in a list in your Kotlin app for Android, while still being future-proof with a library like Retrofit. As a bonus, it’d be great if you could also perform CRUD operations (create, read, update, delete) with the data.
You can choose from basic Java-style HTML requests, or go up to full-scale MVVM design patterns with the new Android Architecture Components. Your source code will look entirely different depending on what approach you chose – so it’s important to make a good choice right at the beginning.
In this article, I’ll show a walk-through using many of the newest components for a modern solution:
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.
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.
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.
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”.
While Sumerian comes with a few ready-made assets, you will often need to add custom 3D models to your scene as well. Currently, Sumerian supports importing two common file types: .fbx (also used by Unity and Autodesk software) and .obj (very wide-spread and common format).
Simply drag & drop such a model from your computer to your assets panel. Alternatively, you can also use the “Import Assets” button in the top bar and then use “Browse” to choose the file to upload.
Where to get these 3D models? Either you create them yourself using Blender, Maya or any other tool. Alternatively, go to great free portals like Google Poly and Microsoft Remix 3D. These objects are usually low-poly and therefore well-suited for mobile phones.
In the first part of the article series, we set up an Augmented Reality app with a host (= avatar). Now, we’ll dive deeper and integrate host interactions. To make the character more life-like, it should look at you. We’ll assign speech files and ensure that the gestures of the character match the spoken content.
But before we set out on these tasks, let’s take a minute to look at some vital concepts of Amazon Sumerian.
Behaviors, State Machines & Events
Unless you want your app to just show a static scene, you’ll need to integrate actions. The trigger for an action could react to interactive user inputs. Alternatively, you define what happens sequentially – e.g., first a new object appears in the scene, then the host avatar explains it.
Technically, this is solved using a state machine. Each entity can have multiple different states. A behavior is a collection of these states. States transition from one to another based on actions & their events (= interactions or timing).
These actions can trigger events. Some examples: the wait time of 5 seconds is over, the movement is completed or the sound file finished playing. Using a transition, you can then transition to a different state.
By combining several states together with transitions, you can make entities interact with the user or perform other tasks to ensure your scene is dynamic.
Many AR / VR use cases involve virtual trainings or guide topics. With Amazon Sumerian, you can quickly create cross-platform apps for these scenarios. The main advantage is the large amount of ready-made content: avatars (called hosts) and virtual environment templates. Through the direct integration of Amazon Web Services (AWS), it’s easy to make the host speak to the user – including lip sync, gestures and even conversations through bots.
Of course, you can create similar solutions with Unity. But Sumerian requires far less prior 3D software knowledge and is therefore ideal for smaller projects as well as prototypes. The interface and generic setup is still quite similar to Unity; so it’s a good evolution to switch to Unity – if needed – after you’ve created your first few apps and services with Amazon Sumerian.
Additionally, right now Amazon is hosting an AR / VR challenge with lots of prizes for the best apps of various categories. So, it’s a great time to explore Sumerian!
What is Amazon Sumerian?
Essentially, Sumerian is a browser-based 3D editing platform. It allows developing for most AR and VR platforms, including Oculus, Vive, Windows Mixed Reality, as well as the browser, Google ARCore and Apple ARKit.
Behind the scenes, it’s based on WebXR. That’s the evolution of WebVR, which was mainly targeting VR headsets. With WebXR, you can access sound, controllers and also anchor objects to the real environment in Mixed Reality scenarios.
Amazon Sumerian Account Setup
First, you need to set up your Amazon account. Amazon offers an AWS free tier, which gives you access to many services and provides some usage quotas for free for the first 12 months. Afterwards, you can still continue using selected services for free. Note that Sumerian is not part of these, but 12 months provides enough time to test & develop your service.
Learn how to access a cloud-based NoSQL database from Node.js. The Azure Cosmos DB stores documents (e.g., JSON) and allows scaling for improved performance plus geo-redundancy with one click. The access interface also allows well-known SQL queries.
Most asynchronous operations like web requests can cause an error. Thus, let’s spend a minute reviewing the basics of the code flow.
In the first part, we took a look at how an algorithm identifies keypoints in camera frames. These are the base for tracking & recognizing the environment.
For Augmented Reality, the device has to know more: its 3D position in the world. It calculates this through the spatial relationship between itself and multiple keypoints. This process is called “Simultaneous Localization and Mapping” – SLAM for short.
Sensors for Perceiving the World
The high-level view: when you first start an AR app using Google ARCore, Apple ARKit or Microsoft Mixed Reality, the system doesn’t know much about the environment. It starts processing data from various sources – mostly the camera. To improve accuracy, the device combines data from other useful sensors like the accelerometer and the gyroscope.