overview of virtual reality, vr, and stereoscopic image recording and viewing.
recording devices are still rare in 2023.
an attachment to lenses or dual lens
two horizontally offset openings that direct the light onto halves of the image sensor
side-by-side: two cameras mounted next to each other
half-mirror: two cameras mounted horizontally offset and also at a vertical right angle (atop or below) with an added mirror to redirect the frontal image to the second camera. a half-mirror lets light pass on one side and reflects it on the other.
for cameras that are too large to be mounted side by side
mirrors necessarily decrease image quality, at least by a small amount, and will require some extra care to be kept clean
the interpupillary distance and the ratio to the distance between stereo images as recorded and displayed has a major influence on realistic depth perception.
if the distance between stereo images is not correctly aligned to the viewers pupil distance, prominent objects may appear similar to looking with crossed-eyes.
near- or far-sightedness persists even with stereoscopic images. glasses or other types of correcting lenses have to be used when viewing so that images do not appear blurry.
required for basic human depth perception are two images taken side-by-side with a horizontal distance close to the interpupillary distance of the viewer. 65mm is a common compromise.
the combined image will retain the same frame dimensions of each individual image. a rectangular image with depth is possible. images can also be taken with a greater field of view using so-called fisheye lenses. this can be used to simulate standing in front of or in a space that wraps around, and allowing the viewer to move the head to look around. this requires a resolution high enough so that the image portion that is actually viewed at any given moment is still detailed enough. a common format for videos with 180 or 360 degrees of view is side-by-side with barrel projection.
the same image compression and file formats as for monoscopic videos are used. the difference to monoscopic videos is that two images are encoded side-by-side.
by image placement
barrel: 180 or 360 degrees of view projected on bent rectangular surface. see distortion
fisheye: 180, 190, or 360 degrees projected onto circles or (half-) spheres
it has to be noted that the full information of the three-dimensional world is not captured by the recording of two two-dimentional images from separate viewpoints. the recording can only reproduce the position and direction of the camera when recording. this means, for example, that when looking at an image, moving the head will not reveal more of the sides of an object. this is also the reason why "stereoscopic" photography is often the preferred term, as saying "3d" recording might be ambiguous.
if the content is actually generated from three-dimensional information, then it is possible with stereoscopy to simulate realistic three-dimensional visual experiences. for example, monoscopic 3d video games calculate the three-dimensional shapes of objects, and project them onto a two-dimensional display relative to the players in-game position and viewing direction, and ideally also considering distance dependent ipd.
more generally called head-mounted displays.
tracking refers to the continual determination of the spatial position of three-dimensional objects. this information can be used to simulate the visual changes perceived when moving through a three-dimensional environment.
two tracking systems have been established:
cameras or other types of sensors inside the headset receive the light or other signals from the controllers to calculate their position
usually requires a well lit room
controllers usually have to be in view of the headset sensors/cameras
the headset builds an internal model of the room to calculate the headset position in the room
full-body tracking refers to tracking the position of the head, arms, and legs at once.
standalone and hybrid
very limited processing power comparable to smartphones
promising upcoming device: bigscreen beyond
directed at apple users because it requires a 200+ euro iphone to buy
extremely compact and lightweight. ~143x52x49mm, 127g
exact dimensions of the parts are public. 3d printed modifications are possible
note that most software assumes and requires two controllers and active tracking.
after comparing the vive pro with vive controllers, the hp reverb g2, and valve index:
htc vive pro 1
hp reverb g2
inside-out tracking which is really not on par with outside-in tracking
vive pro 2
weight and size
field of view
since cables can usually be lead to go behind the head, this is not the biggest issue. however, rotational movements are significantly limited. the players position in the real room can also rotate slowly over time while playing and the cable gets in the way or is moved around. the cable also adds weight
applications where added depth works well: landscapes, waves, caves, interior design, viewing products online, anything where the volume of objects is of interest, 3d animated movies
applications where added depth does not work as well: fast moving objects towards the viewer, unsightly views displayed too close, empty rooms