Environmental HDR Lighting & Reflections in ARCore: Implementation in Unity 3D (Part 3)

Reflective Sphere in Google ARCore with Environmental Mapping

How to make real-time HDR lighting and reflections possible on a smartphone? Based on the unique properties of human perception and the challenges of capturing the world’s state and applying it to virtual objects. Is it still possible?

Google found an interesting approach, which is based on using Artificial Intelligence to fill the missing gaps. In this article, we’ll take a look at how ARCore handles this. The practical implementation of this research is available in the ARCore SDK for Unity. Based on this, a short hands-on guide demonstrates how to create a sphere that reflects the real world – even though the smartphone only captures a fraction of it.

Google ARCore Approach to Environmental HDR Lighting

To still make environmental HDR lighting possible in real-time on smartphones, Google uses an innovative approach, which they also published as a scientific paper . Here, I’ll give you a short, high-level overview of their approach:

First, Google captured a massive amount of training data. The video feed of the smartphone camera captured both the environment, as well as three different spheres. The setup is shown in the image below.

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Environmental HDR Lighting & Reflections in ARCore: Virtual Lighting (Part 2)

FOV of a smartphone

In part 1, we looked at how humans perceive lighting and reflections – vital basic knowledge to estimate how realistic these cues need to be. The most important goal is that the scene looks natural to human viewers. Therefore, the virtual lighting needs to be closely aligned with real lighting.

But how to measure lighting in the real world, and how to apply it to virtual objects?

Virtual Lighting

How do you need to set up virtual lighting to satisfy the criteria mentioned in part 1? Humans recognize if an object doesn’t fit in:

The left image shows a simple scene setup, where the shadow direction is wrong. The virtual object doesn't fit in.
In the ideal case on the right, the shadow and shading is correct.
Comparing a simple scene setup to environmental HDR lighting. Image adapted from the Google Developer documentation.

The image above from the Google Developer Documentation shows both extremes. Even though you might still recognize that the rocket is a virtual object in the right image, you’ll need to look a lot harder. The image on the left is clearly wrong, especially due to the misplaced shadow.

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Environmental HDR Lighting & Reflections in ARCore: Human Perception (Part 1)

Screenshot of the reflective sphere placed in the real world, based on the Environmental HDR lighting by Google ARCore.

Realistically merging virtual objects with the real world in Augmented Reality has a few challenges. The most important:

  1. Realistic positioning, scale and rotation
  2. Lighting and shadows that match the real-world illumination
  3. Occlusion with real-world objects

The first is working very well in today’s AR systems. Number 3 for occlusion is working OK on the Microsoft HoloLens; and it’s soon also coming to ARCore (a private preview is currently running through the ARCore Depth API – which is probably based on the research by Flynn et al. ).

But what about the second item? Google put a lot of effort into this recently. So, let’s look behind the scenes. How does ARCore estimate HDR (high dynamic range) lighting and reflections from the camera image?

Remember that ARCore needs to scale to a variety of smartphones; thus, a requirement is that it also works on phones that only have a single RGB camera – like the Google Pixel 2.

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Using Amazon Sumerian in Trainings and Classrooms with AWS IAM

In this article, we’ll configure AWS Identity and Access Management (IAM) to easily use Amazon Sumerian with multiple users. This is especially important for classrooms or trainings. You often don’t want to loose time by having attendees set up and activate their own AWS accounts, including their personal credit cards.

Instead, by setting up sub-users in your account beforehand, you have complete control over the experience and can get started right away. Additionally, it helps with troubleshooting for exercises.

Right now, no ready-made AWS Educate classrooms are available that support Amazon Sumerian. If that changes, the classrooms would be a good alternative, as it gives students their own free AWS credits instead of everything billed to a central account.

Securing Your Account

The first step is making sure you own root account is properly secured. A major part is enabling Multi-Factor Authentication (MFA) for your root account. Especially when working in teams and with source control, it’s an easy-to-make mistake to upload your credentials somewhere; you don’t want others to have full control over your whole AWS account, as this can incur major charges to your credit card. Therefore, it’s best to enable MFA before you continue.

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Hit Test & Augmented Reality Anchors with Amazon Sumerian (Part 3)

Three call-backs to get from a touch event to a registered AR anchor in Amazon Sumerian.

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.

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Augmented Reality Anchors and Amazon Sumerian’s ArAnchorComponent (Part 2)

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:

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Augmented Reality Object Placement with Amazon Sumerian (Part 1)

Repositioning your AR objects on the floor with Amazon Sumerian

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.

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Create engaging Healthcare Experiences with Augmented Reality

Create engaging Healthcare Experiences with Augmented Reality - Amazon Sumerian

Download hands-on workshop slides and material for a complete getting-started guide to your first 3D experience – with a background in digital healthcare!

Conference Session

The build.well.being conference is an annual networking event for the doers in Digital Healthcare. The fast-paced event compresses a lot of useful information into a short day: sessions from health professionals (including a keynote from Brian Anthony, associate director at the MIT.nano). Student project pitches. Plus: hands-on workshops.

Amazon Sumerian Workshop @ build.well.being, © FH St. Pölten | Tobias Sautner
Amazon Sumerian Workshop @ build.well.being, © FH St. Pölten | Tobias Sautner

Together with Anna Runefelt, I was running a challenging workshop: introducing attendees with a healthcare background to the world of Augmented / Virtual Reality. The aim of the hands-on workshop: creating your first live 3D experience in about 1 hour. This was possible thanks to the easy-to-use interface of Amazon Sumerian. Most of the attendees who followed along indeed managed to get a fully working 3D scene running on their laptops.

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Download, Export or Backup Amazon Sumerian Scenes (Part 6)

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?

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Animation & Timeline for AR with Amazon Sumerian (Part 5)

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.

Animations in the Digital Healthcare Explained prototype, captured in Augmented Reality running on a Google Pixel with ARCore

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.

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