Ergonomics of People and Places

Ergonomics of People

Physical Human Embodiment

One of the most interesting areas of study is that of human proportion. In order for our content to adapt to human needs an behavior, we need to be aware of the extent of the physicality of humans. Below are two really great schematics that showcase that a lot of human movement happens in arcs around us and ranges in length between different types of people.
The Measure of Man and Woman: Human Factors in Design, by Alvin R. Tilley, Henry Dreyfuss Associates, 1993.
The Measure of Man and Woman: Human Factors in Design, by Alvin R. Tilley, Henry Dreyfuss Associates, 1993.
A more common understanding of the range of motion on the human body can be seen by observing the types of joints that make up our skeletal structure, and the musculature of the human body. I would highly recommend checking out these types of resources if you're interested in elevating your understanding of how to prevent fatigue.

Design for Curves

As physical ability is based on arcs of human movement, and spatial design is based on the volumetric sphere around the user, we can see a pattern emerge on the types of interfaces that work best within the confines of spatial computing: curves.
One of the most called upon structures in current interface design is that of the screen directly in front of the user. However, when we put said screens into VR/AR environments and enlarge them for comfortable viewing these screens tend to clip at the edge of a user’s comfortable FOV. Because of this, large interfaces that are placed directly in front of the user, like televisions or control panels, are placed in an arc to curve around the user. Content at the top of this curved screen is also often tilted downward to face the user, and content at the bottom of this curved screen is tilted upward to face the user.

Common Ergonomic Issues in VR/AR

Ergonomics is a key aspect of user comfort. Muscle fatigue is common in spatial interfaces as we are requiring our user to contribute to the digital content in ways they have not been asked to previously. It can be taxing for muscles to support mobility (moving about in space), dexterity (precision and flexibility), and stamina (prolonged or retained movement) at the same time. For brevity’s sake, I will be focusing on shoulder, arm, wrist, neck, and eye movement as those are oftentimes the most taxed in VR/AR systems.

Shoulder, Arm, and Wrist Ergonomics

Human hands are incredibly well built for micro-interactions (like typing on a keyboard), as well as arms and shoulders macro-interactions (like swinging a tennis racket). However, problems occur when we over-tax muscle groupings for stamina, mobility, and dexterity concurrently. Engaged positions for shoulders and wrists over long periods of time are not advisable for a positive user experience.
For arm and shoulder comfort, keeping interactable content at low torso height is advisable so that we aren’t over-extending the user's muscles. There are many variables for wrist comfort that depend on the selection of input, as hand input utilizes the wrist in a different way than controllers or other peripherals do. A core concept to remember is that we want game mechanics to be repeated in multitude over time, so make sure to take into consideration resting positions to help usability.

Neck Ergonomics

Necks are an incredibly complex muscular infrastructure connecting your head to your shoulders, but these muscles do have limitations. Although the neck is flexible, maintaining this flexibility over time can be exhausting for neck muscles.
Illustration provided by Dr. Ken Hansraj, Spinal and Orthopedic Surgeon
Avoid placing content for long periods outside the defined center of the field of view (FOV), because users might have to engage their neck to hold this turned position.

Eye Ergonomics

Eye strain is a common occurrence as we digitally attempt to convey depth. Not many think of the eye when considering human movement but your eye is actually composed of an intricate grouping of muscles all working in succession and collaboration with one another.
Diagram from article entitled “What are survey accurate visual simulations?” by buildmedia
Many users will want to closely inspect objects or read text on top of content. However, this is fatiguing to the eye as it might induce double vision, disturb head space, or even break immersion if the object has a large volume and starts clipping into the device.
To help with this, when users bring objects close to them, lock at a distance from the user’s head. If the object is incredibly large and still clips through the device, it might also be beneficial to have a 2D render replace the 3D model and scale that render instead of the object itself.
Many VR/AR games employ interfaces and interactions at multiple locations around the environment. Be mindful that when this happens at a variety of depths, like in the foreground, midground, and background, you are requiring your user to perform constant refocus operations. Have interfaces that are associated with objects, next to those objects. If that can’t be done, then designing an interface that has the ability to be manually placed by the user that moves between coordinate spaces is the best option.

Ergonomics of Places

Considerations towards Physical Environment

This This is more a stereotypical practice for AR, but I think it couldalso be valuable for environmental design in VR as well. The activity is similar to that of personas, but to consider specific places of interaction for your content and how that environment might change the experience itself.
Example: When creating an augmented reality app, what is the ideal location? How might these interactions change between someone who is viewing it in their living room, outside in a park, in an elevator, in a cafe, or in an auditorium?
These locations have contextual meaning based on size of the space available, but also the potential for objects and people occupying them. Considering a non-typical playing environment, or even the impact of architecture and city planning, is important as this medium evolves.

Acclimating to a Virtual Environment

Users now have digital objects that persist spatially in front of them that are engaging, but users consider this to be a new environment. Due to this, your user might succumb to freeze factor. Freeze factor is an overwhelming feeling due to the amount of information (or lack thereof) that a user is receiving, and thus they stand in the same location.
Give the user time to process visual information, onboarding cues to help them understand the input schema, visual affordances and effects that distinguish digital content from the physical scene, and auditory feedback to encourage a continuation of interaction.

The Scale of Experience

One of the largest shifts in thinking is that we as designers are not relegated to the confines of dimensionality any longer. Content in VR/AR could be anywhere, in any environment, in any form. This game could be at Object-Scale, Tabletop-Scale, Room-Scale, or City or World-Scale Experiences.​
Regardless of types of scale, pieces of content that populate within a user's environment should still maintain safety for the player and respect the bounds of the physical world.