Causes of discomfort in VR, and how creators resolved them — Part 1
I’ve been learning about XR during this Pandemic for a while now. This article will be the first of many where I aggregate all my learnings of XR design best practices with real-world examples and my personal experiences.
One of the most intriguing aspects of Virtual Reality is its immersiveness and it for sure comes with a problem — simulation sickness.
The main reason for this discomfort comes from the conflict between what you see and what you feel. Another similar conflict that we’re more familiar with is motion sickness: When you look down at your phone in a car, your body tells you that you’re moving but what you see is relatively still. That still-moving conflict is what causes motion sickness.
When we’re talking about virtual reality, with providing an immersive experience as the primary goal, I’ve categorized all causes of simulation sickness into these 2 categories:
- What you see does not live up to what you feel
- What you feel does not live up to what you see
It might look like these 2 are referring to the same thing but they’re not. With building an immersive virtual reality as the goal, each of them has different tactics for resolving the problem.
What you see does not match what you feel
In this category, the visual is the one to blame and to fix.
1. Frame rate can’t catch up with the head movement
When the framerate drops below 60 FPS, users will notice the lag between their body movement and the image shown which causes discomfort.
This caught people’s attention when the first generation of 6 DoF VR headsets got launched and companies were still optimizing the hardware：
Nowadays it happens more often when apps/games are under development and creators and engineers are pretty good at discovering and resolving it.
2. 360 3D content can’t respond to 6 DoF movement
When viewing 360 3d movie content in a 6-DoF VR headset, one will definitely notice something is off when moving their head around.
One of the cool features for VR headsets is viewing 360 3D videos. When viewing these videos, as your head moves on x/y/z, the whole “world” will unnaturally move with you.
This particular type of discomfort is rarely mentioned but I personally feel it pretty strongly. What’s missing from the experience is the parallel movement of objects in the virtual world.
When wearing a 6 DoF headset, people are used to utilizing these 2 things to generate the perception of depth: Stereopsis(Binocular) and the Motion parallax. Most 360 3D movies can create the former but not the latter. Because of the way our eyes are positioned in the head, it’s nearly impossible to only make the yaw/roll/pitch movement without changing the x/y/z position. That’s when the conflict happens: what you see does not match what you feel.
It got really amplified when I was trying the Space Explorer where spatial UI elements are also present:
In this particular view shown below, it has natively generated UI elements surrounded by an immersive 3D 360 video. The gif shows my head making forward and backward movements. What’s causing my discomfort is the clashing of these 2 types of content. the human floating in the background is actually collapsing with the title text while in reality, I know when I’m making movements like this, this would not happen. And that’s how it causes my sickness.
How people resolve this:
There is some amazing work going on from Google to upgrade the capability of shooting 360 3D videos to include light field information so people can actually experience the motion parallax while watching the video:
Before that tech becomes more accessible, it’s best to avoid displaying a frame of a 3d 360 video with objects positioned too close to the viewer, especially when 3D UI elements are also present.
As you can see from the graph below, the effectiveness of motion parallax creating the depth contrast will drop as objects are positioned further away. So the further the objects are, the fewer people will notice the parallax is missing, minimizing the discomfort.
What you feel does not match what you see
In this scenario, visuals are pretty realistic, almost too realistic that your brain is confused with signals from your body sensors from the real world…
I’m glad you’re interested in this topic! Please find part 2 here:
