Welcome to the presentation of our paper "Kaboom !!! Visually Exploring Latency Measurements for XR"
So what is latency?
it is defined as a delay
in a system
in XR we most often look at the motion to photon latency
which is the time between a motion
which gets tracked
fed into a simulation
to render the next image
which is then shown
on the screen
latency becomes a problem if it is too big
like
if you walk in VR
see that there is a wall approaching
but your virtual image lags behind
so
the wall is closer than you anticipated
or
also unpleasant
latency can make you sick
to know that latency is too high, we need to measure it
there are many approaches
some easier to conduct than others
some more precise
our paper provides a visual overview
of how to measure latency
the visual representation allows to quickly understand the concept of an approach
and compare similarities and differences between approaches
let's dive into some selected approaches
to understand them
to measure motion to photon latency
you need to observe a motion
and its respective counterpart on a screen
you either do this
with one camera
or
you observe the motion and its effects
with two different, synchronized devices
the most simple approach is frame counting
as described by He et al.
they move a tracked wand in front of a screen
the screen shows the virtual counterpart
a camera records the scene
the video is analysed to find when the wand overlaps a line on the screen
and when the virtual wand overlaps the same line on the screen
the time
that has passed between the events
is the motion to photon latency
alas
frame counting is limited by the camera's temporal and spatial resolution
Sine Fitting overcomes problems caused by a lacking camera resolution
by using the predictability of a pendulum
Steed attaches a tracked object to a pendulum
and its position is rendered on the screen
a camera records both
the real and the virtual pendulum
the positions are extracted via thresholding
he fits a sine curve
to each to correct inaccuracies
the motion to photon latency
can be calculated from the phase difference
alas, Sine Fitting is limited
for example
when using virtual reality head mounted displays
their screen's image is distorted by lenses
preventing a clear recorded image
if a camera needs to record both a real motion and a screen
see our paper to find more illustrations of latency measurement approaches
we were asked
in the reviews, why we chose
the visual style
we research latency in XR systems and how to measure it
part of it is to read scientific papers of other researchers
remembering what each paper is about becomes harder
the more there are
so you write notes
the problem is how to write notes to remember
because many papers means many notes
one thing is special
with those papers
there is always some physical apparatus in the center of attention
we created sketches
which helped to see how the approaches are similar to one another
and how they differ
the sketches allowed to compare
sort and categorize latency measurement approaches
the visual overview helped us in our research
and we want to make it available to others
to help them as well
it is important to note
that this paper is no substitution for an in-depth written literature overview
it is more an addition to the more textual treatments
it may ease entering the topic for scholars not yet familiar with it
and we believe that this topic is important for many