Asynchronous reprojection is a class of
computer graphics
Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...
technologies aimed ensuring a
virtual reality headset
A virtual reality headset (or VR headset) is a head-mounted device that provides virtual reality for the wearer. VR headsets are widely used with VR video games but they are also used in other applications, including simulators and trainers. VR ...
's responsiveness to user motion even when the
GPU
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...
isn't able to keep up with the headset's target
frame rate
Frame rate (expressed in or FPS) is the frequency (rate) at which consecutive images (frames) are captured or displayed. The term applies equally to film and video cameras, computer graphics, and motion capture systems. Frame rate may also be ca ...
.
Reprojection involves the headset's driver taking one or multiple previously
rendered frames and using newer motion information from the headset's sensors to
extrapolate
In mathematics, extrapolation is a type of estimation, beyond the original observation range, of the value of a variable on the basis of its relationship with another variable. It is similar to interpolation, which produces estimates between know ...
(often referred to as "reprojecting" or "warping") the previous frame into a prediction of what a normally rendered frame would look like.
"Asynchronous" refers to this process being continuously performed in parallel with rendering, allowing reprojected frames to be displayed without delay in case a regular frame isn't rendered in time.
The use of these techniques allows for a lowering in the video rendering
hardware specifications required to achieve a certain intended level of responsiveness.
Variations
Various vendors have implemented their own variations of the technique under different names. Basic versions of the technique are referred to as by
Google
Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...
and
Valve
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
,
while
Oculus Oculus (a term from Latin ''oculus'', meaning 'eye'), may refer to the following
Architecture
* Oculus (architecture), a circular opening in the centre of a dome or in a wall
Arts, entertainment, and media
* ''Oculus'' (film), a 2013 American ...
has two implementations, called
and . Asynchronous timewarp uses the headset's rotational data to extrapolate a new rendered frame based on the last frame it received. Asynchronous spacewarp additionally uses
depth information to help compensate for perspective and other geometric changes.
Valve's early version called ''interleaved reprojection'' would make the application run at half frame rate and reproject every other frame.
A later variant by Valve is ''SteamVR Motion Smoothing'', which builds upon regular asynchronous reprojection in being able to reproject two frames instead of one.
See also
*
2D to 3D conversion
2D to 3D video conversion (also called 2D to stereo 3D conversion and stereo conversion) is the process of transforming 2D ("flat") film to 3D form, which in almost all cases is stereo, so it is the process of creating imagery for each eye from ...
References
Virtual reality
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