Virtual Reality Design Principles: Starting Up, User Attention, and Comfort Zones
When designing for virtual reality (VR), it is important to follow best practices to improve the user experience. The term design principles refers to a set of ideas or beliefs that are valid in all projects of this type. For virtual reality, these principles differ from traditional design.
Some examples of design principles within 2D design include designing on a grid or creating a visual hierarchy of information to direct users to the most important information first. These principles, or agreed-upon standards, are created over many years, after much trial and error. And while these principles can be broken, they should be broken only for good reason.
Since VR is a new field, those who develop VR content are still in the process of discovering its design principles. Often times, in order to figure out which design principles work well, you have to figure out what doesn’t work well. Best practices and standards will emerge over time as the VR community grows and more consumer VR applications are produced. In the meantime, there are a number of generally agreed-upon standards for virtual reality, no matter what platform you might be designing for.
Best practices for starting your own VR experience
When initially entering into an experience, users often need a moment to adjust to their new virtual surroundings. A simple opening scene where users can adapt to the environment and controls can be a good way to help them acclimate to your experience. Allow the user to familiarize themselves with your app and only go to the main app experience when they are ready.
Focusing the user’s attention in virtual reality
Virtual reality is much less linear than experiences inside a traditional 2D screen. In virtual reality, you should give the user the freedom to look and explore the environment. This freedom of exploration can make it tricky when you need to draw the user’s attention to certain parts of your app.
The director in a 2D movie can frame the user’s vision exactly where they want it. As the director in a 3D space, you have no idea if the user might want to face your main content or focus on another part of the scene. You can’t force the user to look in a particular direction – forcing users to see virtual reality is one of the quickest ways to trigger mimesis.
However, there are a number of ways to focus the user’s attention where you want it. Accurate 3D audio cues can direct the user to the area where the procedure is taking place. Lighting signals can also be used. For example, you can catch the user’s attention by lightening the parts you want them to look at and darkening the parts you want to deemphasize. Another approach is to redirect the same content within the app to match the direction the user is facing.
In what may be the easiest solution, some applications simply place messages in their 3D environment to instruct the user to turn around and face where they want to focus the user’s attention. This technology is also used in room level games where the user may have only a limited number of sensors available to track their movement in the real world. It can be easy to get around in virtual reality at a room scale, and placing a message can help the user reorient themselves in relation to sensors in the real world.
No matter how you choose to deal with user focus, be aware that in virtual reality users should have freedom of choice. This freedom of choice can conflict with what you would want them to do. Finding ways to allow this freedom of choice while also focusing on the user where you want them is a vital part of a well-designed VR experience.
Understanding the comfort zone in virtual reality
With the traditional 2D design, the user interface (UI) was restricted to certain canvas sizes. Whether it’s browser size or screen size, something has always put a limit on the dimensions your UI can be. Virtual reality removes those limitations. Suddenly a 360-degree canvas is at your disposal to design! The user interface can be anywhere and everywhere!
Before you start rolling out 360-degree interface elements around your users, there are a number of best practices to keep in mind to make your experience comfortable. If a user has to rotate their head a lot, make an effort to read the text of the interface, or move their arms in an attempt to use your UI, it will most likely result in a poor VR experience and cost you users.
Alex Chu from Samsung Research, in his presentation “VR Design: Moving from a 2D Design Paradigm to a 3D Design Paradigm,” provides a number of measurements for the minimum, optimal, and maximum distance that should appear away from the user. In the presentation, Cho discusses the optimal distances for viewing a 3D object.
As objects get closer to your face, your eyes will begin to strain to focus on them. At a distance of about 0.5 m from the user and closer is the distance at which this strain begins to occur; Oculus recommends a minimum distance of 0.75 meters to prevent this strain. Between that minimum distance and about 10 meters is where the strongest sense of stereoscopic depth perception occurs. This effect begins to fade between 10 and 20 meters, and after 20 meters, the effect basically disappears.
These restrictions give you 0.75-10 meters of space in which to display the main user content. The closeness of the content will strain the eyes of the users, and anything further than that will cause you to lose the 3D effect you are trying to achieve.
As the accuracy of VR headsets improves, the stereo effect may be kept further away from the user, 20 meters or so away as the effect disappears today. For now, the 20m mark is still a good base for content design.
In his presentation “Pre-Visualization Methods for VR Interface Design,” Google VR designer Mike Alger also discusses the range of motion that users can comfortably rotate their heads both horizontally and vertically. Chu and Alger report that the range in which users can comfortably rotate their heads horizontally is 30 degrees, with a maximum rotation of 55 degrees. Combined with the field of view (FOV) of top-level tethered headphones (with an average of 100 degrees), this gives the user a range of about 80 degrees to each side for comfortable viewing of main content, and about 105 degrees to each side for surround content. When displaying content to users, focus on keeping your main content within the user’s comfortable horizontal viewing area.
As the headphones’ field of view improves, the values will change to allow more visibility to the side. However, it should be noted that most headphones (with a few exceptions such as the Pimax) seem uninterested in significantly improving the field of view in the next second generation of devices. Regardless, you will be able to use the same calculations to determine your comfortable viewing area yourself in the future.
Likewise, there is a comfortable range of motion for users to rotate their heads vertically. The comfort zone here is about 20 degrees upward comfortably, a max of 60 degrees up, and down comfortably about 12 degrees and a max of 40 degrees.
Although horizontal head movements are a minor annoyance, vertical head rotation can be very stressful for the user to hold for extended periods of time. The vertical field of view of headphones is also not usually deployed, so it is rounded here. On some headphones, it may be smaller. As a best practice, try to keep the user’s vertical head rotation to a minimum to achieve a more comfortable user experience.
Using the above information, you can create a set of instructions for placing VR content that is relevant to the user. You can place content anywhere you want, of course, but important content should stay within areas where horizontal and vertical comfort zones and viewing distance converge. Content in areas outside of these areas is less likely to be seen. If you are creating content that is meant to be hidden, or can only be discovered through deep exploration, areas outside your comfort zone can be good areas to place that content. However, avoid keeping your content there once you discover it. If a user has to click on your content, it won’t stay in your app for long.