Virtual User Experience (VX) General Guidelines

Introduction

What is User Experience?

International Organization for Standardization defined user experience or UX as a person’s perceptions and responses resulting from the use or anticipated use of a product, system or service. The product need to be designed centered on the users in order to have a great user experience. Product with a great UX required to have these components:

  • Useful: Product should be original and fulfill a need
  • Usable: Product must be easy to use
  • Desirable: Product design, such as image, identity, brand, and other design elements are used to evoke emotion and appreciation
  • Findable: Product should be navigable and locatable
  • Accessible: Product should be accessible to people with disabilities
  • Credible: Product must be trustable.

Complete guide of UX can be seen here: https://www.interaction-design.org/literature/topics/ux-design 

Source: https://www.usability.gov/what-and-why/user-experience.html

What is Virtual Reality?

Oxford defined virtual reality or VR as the computer-generated simulation of a three-dimensional image or environment that can be interacted with in seemingly real or physical way by a person using a special electronic equipment, such as helmet with a screen inside or gloves fitted with sensors. Currently, virtual reality application have been developed for education, training, simulation, entertainment, gaming, etc. Virtual reality bring the user to the virtual environment where they can experience a lot of things like a real things. The example of virtual reality application are VRChat where people can socialize with each other using a virtual avatar, and Beat Saber which is a rhythm game in virtual environment. To access a VR application, user need to have a high-spec computer and a VR Head-Mounted Display (HMD) such as Oculus Quest and HTC Vive.

What is Virtual Experience?

Virtual Experience or VX is a user experience inside a virtual environment. Combined with International Organization for Standardization definition, VX can be defined as a person’s perceptions and responses inside a virtual environment resulting from the use or anticipated use of a virtual reality application. To create a VR application with a great VX, the application need to be designed centered on the users need. VR hardwares and softwares is still developing, so it is a challenge to design a VR application which maximize the user’s perception and immersion without causing a cybersickness.

VR Important Component

Visual – Sense of Sight

This is what users can see inside the virtual environments. The important aspect of the visual component on the virtual reality are listed below:

1. Interpupillary distance (IPD)

The distance between the centers of the pupils of the eyes measured in millimeters. Everyone has different IPD value. The modern HMD such as Oculus Quest and HTC Vive have a setting to adjust the IPD value for each user. IPD value is important to prevent eye fatigue and headaches — since the center of the lenses of the HMD is positioned correctly relative to the centers of your pupils. If the VR application plays with 3D distances and perception, IPD value is really important. However, for other types of applications, IPD value usually was set to be 63mm which is the average value of adult IPD. Click this link to see the tutorial on how to measure your own IPD: https://www.wikihow.com/Measure-Your-Interpupillary-Distance. There are some Android and iOS applications that can help you to measure your own IPD such as GlassifyMe.IPD

Fig 1 illustrate the IPD distance of the person eyes. Image courtesy of https://endmyopia.org

2. Text and Button Sizes

The text and button size for virtual reality applications should be consistent. The text and button should be readable and not too small. The picture below explains the recommended text size and button size using a unit called distance-independent millimeter (dmm). 1 dmm can be described as 1mm out of 1m away, or 2mm out of 2m away, or 0.5mm out of 0.5m away. Click this link for more detailed information: https://youtu.be/ES9jArHRFHQ?t=480

dmm definitiontextsize & hitsize
Fig. 2 the recommended text and button sizes for VR application. Image taken from https://youtu.be/ES9jArHRFHQ?t=1205.

3. UI Screen in VR

The interesting part of screen design in VR is that we can contour the screen as what we would like it to be and place it wherever we want it to be as shown in Figure 3.

3 types of UI screen inside VR
Fig. 3 The variation of the screen contour in VR. Image taken from: https://youtu.be/ES9jArHRFHQ?t=790 

4. Visual Feedback

Visual feedback is really important in virtual reality user experience. Visual feedback can help with:

  • To make sure that the user knows what they selected of inside a virtual environment
  • Increase the immersion of the user inside a virtual environment
visual feedback
Fig. 4, The example of the visual feedback of a screen menu. GIF taken from: https://youtu.be/ES9jArHRFHQ?t=854

5. Converting Images into VR assets

  • 1px image = 1dmm
    pixel in dmm
    Image taken from: https://youtu.be/ES9jArHRFHQ?t=1073 
  • Keep primary UI elements within 60 degrees, since no matter how wide the field of view is, if the user did not move their head around, they will see things comfortably within a 60 degrees area horizontally and vertically.
  • The outer circle which is around 120 degrees is the comfortable area where the person’s eyes can move including the neck.
  • Usually, a person’s head looks down at around +10 degrees to +15 degrees (horizon line) and our eyes tend to look up. So a comfortable visual center ends up being around +6 degrees below the horizon line.
  • If the UI center on the horizon line, the user will feel that they have to look up to see the UI
    visual centerImage taken from: https://youtu.be/ES9jArHRFHQ?t=1157.  
  • Example of prototype UI design for VR:
    ui design prototypeImage taken from: https://youtu.be/ES9jArHRFHQ?t=1284

6. UI Position in the Virtual Environment

Auditory – Sense of Hearing

1. Human Comfort Sounds Level

References: https://safetyguide.web.cern.ch/SafetyGuide/Part3/25.2.html

  • Hearing threshold 0 dB
  • Quiet conversation 25 dB
  • Comfortable sound level 40-60 dB
  • Noisy restaurant 70 dB
  • Intense street traffic 90 dB Lower limit of possible injuries
  • Jet engine at 25 m 120 dB Threshold of pain

2. 3D Spatial Sound

The complete guide can be seen at https://www.youtube.com/watch?v=IAwFN9sFcso

Important point: Do not use Unity Audio settings since it does not simulate properly in VR! Use whatever Spatialize plug-in that available in the market (Oculus Audio SDK, Steam Audio VR, etc)

  • Must using Head Related Transfer Function (HRTF)
    The effect is that the user can tell from which direction the sounds come from. Possible with head tracking. HRTF will increase realism and immersion. HRTF settings are different for each person due to different distances between the left ear and right ear. However, the current technology has not been able to adjust the ear’s distance. All HRTF Content must be mono since it comes from a different source point.
  • The sound source must be located in the correct position.
    mono soundImage taken from: https://youtu.be/IAwFN9sFcso?t=539
  • The attenuation curve of the sound source must be correct.
    Therefore the user can tell how far away the sound source is.
    attenuation curveImage taken from: https://youtu.be/IAwFN9sFcso?t=653.
  • Dialog has to come from the people’s mouth. (Place the sound source on the avatar mouth)
  • For voice over, try to make the sounds come from something (for example from AruBot)
  • Reflection settings are important for indoor environment
  • Music comes out from an object (e.g. a speaker) in the virtual environment
  • Non-spatialized music — most suitable for background music, which is a stereo but not too loud.

3. Oculus Audio SDK

Haptic – Sense of Touch

Olfactory – Sense of Smell

Sense of Taste (Not yet commercialized)

  • Still in the early stage of development
  • Sense of taste feedback can increase the user’s immersion
  • Until the time this guide is written, there is no commercialized product available in the market.

Locomotion

Explain how users navigate themselves within virtual environments.locomotion

References: https://ieeexplore.ieee.org/abstract/document/8446620

Steering (Natural Walking)

Jumping

Teleport

Cybersickness

Effort to reduce cybersickness

(Riska Wilian T. P. – News)