Part 5: Common Problems and Causes

Christiane Snyder
7/4/2016

Screen Door Effect(SDE):

Also known as fixed-pattern noise(FPN) is a visual artifact or error found in VR headsets, as well as other displays like projectors. Fine lines between each pixel are visible, creating a grid-like effect over the image.

Cause:

Generally caused in HMDs with low resolution. Due to increased resolution quality, this issue is becoming less frequent. Can still be seen in Oculus Rift DK1 and DK2, as well as the Samsung Gear.

Solution(s):

Sadly, this is caused by the headset itself and cannot really be fixed for the older headsets that have it.

Latency:

The delay between action and reaction. Visual lag between when a user moves their head and what they see with the HMD.

Solution(s):

This can be solved or improved by improving the refresh rate, creating some type of system to predict when your user will turn their head and using it to pre-render the images they are about to see ahead of time, if you’re using the Oculus Rift make use of Timewarp or decreasing Pixel switching time.

Simulator Sickness:

Motion sickness that occurs during a VR experience that is caused by visual stimuli. This is one of the largest issues in the VR field and HMD companies are working very hard to eradicate it from their products. The symptoms associated with simulator sickness can be very uncomfortable for users, so designers and programmers should always avoid the practices that cause it.

Cause:
occurs when the user’s head movement does not match up with the visuals being provided by the HMD.

Possible Direct Causes:
  • Large changes in velocity or uncontrollable acceleration or jerkiness
  • The system lost track of the headset position
  • Lack of control from user
  • Using VR headsets for extended periods of time
  • Users field of view is lower than it should be in-experience
  • Too large of FOV
  • Excessive lag or high latency
  • Flashing images or sudden significant contrasts in light
  • Each individual has difference tolerance of simulator sickness and some may have differing reactions to certain stereoscopic stimuli.
  • Solution(s):
  • Avoid quick or large changes acceleration and deceleration. Try to use constant velocity when possible.
  • Head set tracking should always be active, there is a risk of simulation sickness if isn’t calibrated even for a very short time. If your application loses track of a players head at any point in the experience, it is extremely likely that what they see will not match up with what their brain is expecting to see.
  • Try to make sure that game mechanics move the camera from the player’s control as infrequently as possible, if at all.
  • Encourage appropriate time usage.
  • Ensure users field of view is not directly on the ground.
  • Ensure your experiences display field of view is not too wide.
  • Make sure your app does not lag or drop frames on systems that is should be able to handle it. (If is currently doing so then it’s an issue in your design or programming)
  • Avoid bright contrasts of light (black to white) and flickering colors or images.
  • Ensure that the screen never freezes during gameplay or in-experience, if a transition is needed, make sure to maintain audio.
  • If the hardware you are using only allows seated experiences, ensure that the mechanics of the game fit with the player remaining seated. (i.e. they don’t see themselves running in VR when they are stationary)