Richard Yao - Human Visual System & the RiftSeptember 19, 2014
Reminder from Richard: you should read the Best Practices guide
Human Visual System
Visual perception is active - constantly perceiving, resolving objects
Rift provides all of your visual perception - big responsibility - have to consider the experineces you’re building for people
how we perceive:
bottom up processes (raw information coming in from the world) - points of light etc. built into lines, shapes
top down processes - originate in your brain, act on information, help you parse/interpret it.
interpretation - turning all this information into something sensible, making sense of what you’re looking at.
images grouped into discrete objects
start to notice things when objects become ambiguous - illusions of duck vs/ rabbit, etc.
illusions are interesting, because we learn things when perceptions break down.
table illusion - 2 tables w/ same shape but look different sizes
change blindness - don’t notice when mountains change in background of city image. because there’s a gray image flashing in between, we don’t notice. if it flickers immediately we notice immediately.
lesson #1: perception is interpretation. a lot escapes awareness - stuff happening in your head/the world, you don’t know it or notice it. ‘metacognition’ - cognition about cognition
- really important to test everything for the rift - don’t know what we don’t know.
Bodily Sensory Information
vestibular system detects acceleration - “sense of balance” - tells you which way is down.
proprioceptive system - receptors in your muscles/joints, help your brain compute where your body is, how it’s positioned.
vestibulo-ocular reflex (VOR) - bodily senses drive eye muscles, drive what your eyes are doing.
VOR disagreements - what gets displayed on the screen must update when your head moves.
Tons of ways this can go wrong - bad distortion, bad head model, static image, lost position tracking, judder, dropped frames, etc.
your mind expects taht visual information at the point of gaze will stay still - if you have problems, your visual information will wiggle. your brain interprets this as the entire world moving -> sickness
lesson #2: small rendering issues become very very important
vection - illusory perception of self-motion from vision. “Vision tells you that you’re moving through space, body perceives you sitting in chair, this causes discomfort.”
- Head based control - Head movements can steer your avatar. provide a vestibular input to line up the senses
avoid using head tilt to rotate in place - induces “coriolis effect” when your body rotates on one axis and your head is tilted. causes dizziness - same effect as dizzybat.
even in a perfect VR implementation, sensory disagreements will cause discomfort. camera movement is the primary cause. non-player-controlled camera movement is worse
acceleration is the main culprit of vection
More comfortable experience if you can prevent conflict between senses, vision
“Optic flow” causes vection - coherent movement in your visual field that suggests movement.
Keeping people engaged with a task, keeping mind occupied reduces vection.
Effortful re-interpretation: the cockpit is a frame of reference, reminds you that you’re sitting stationary in a chair.
blocking off periphery in a demo. didn’t help much, still felt like you were moving through space.
2nd try - put it on a TV in a virtual room in the Oculus. much more effective tool at fighting vection
provide an “inertial reference frame”
player locked skybox - you flip the interpretation your mind defaults to. “I must be moving through the world” becomes “I must be sitting and the world is moving around me”
demo with background staying rock solid as player moves head - seems to help a little bit. might not make sense in different types of content. cons - not clear what the best practices are. what’s the best locked background, etc.
you can see the gridlines through the ground, it’s a little transparent
brain interpreted the gridlines as stuck inside a cage & flying around in a yellow cage.
challenges and opportunities
content design - easy to make people very uncomfortable
creative solutions - yet to be discovered, things that haven’t been tried or things we don’t know that can hurt/help comfort.
Everything is still evolving… stay tuned.