VR headset with or without cable? When do I need wired or mobile VR glasses? What is tracking anyway, which variants are there? What performance differences do VR glasses have? And how is all this related to each other?
VR headsets have the following distinguishing features
- wired and standalone
- 3DoF and 6DoF
- external und internal tracking
Distinguishing features of VR-Headsets
VR headsets are either wired or standalone. Wired VR headsets always require a workstation, i.e. a PC or notebook with the corresponding power. These headsets are usually lighter, since processors and batteries for the power supply do not have to be integrated. Image signal and power supply take place via the cable. However, some wired headsets can be upgraded with batteries and wireless modules to operate without cables, but a PC is still needed as a base station. A standalone headset can – as the name suggests – be operated without an additional workstation. The entire technology is built into the headset and is used according to the plug-and-play principle. However, a standalone headset can optionally be connected to a workstation in most cases to get an improved performance.
The decisive difference between the two variants is the performance. Wired headsets always rely on the power (processor and graphics card) of the workstation. The image signal is then sent to the headset via the cable (via the wireless module if upgraded accordingly). Tracking information (i.e. the current room position) of the VR goggles is sent back to the workstation via the cable. Standalone goggles can only rely on the limited computing capacity of the internal processor. Therefore, the performance, battery life and thus also the resolution of standalone headsets is limited.
We have explained the two different degrees of freedom of movement 3DoF and 6DoF in detail in this blog article. If you use a 3DoF headset, you do not need any tracking. If you use a headset with 6DoF, the position of the VR goggles has to be detected by internal sensors or external tracking systems: In VR tracking, the real user movements are detected by sensors and transferred to the virtual world. The required sensors are partly integrated in the VR glasses (see comparison in the table below) and track the head movement there (so-called head tracking), among other things.
To determine the position in space (6DoF), there are two tracking variants:
With external tracking, “devices” are set up in addition to the VR goggles and the PC, which “observe” movements in the tracking area. The base stations of the Valve Index [or HTC Vive] can be mounted on the wall or on tripods, for example.
Bild 4: Infrared transmitter for an external tracking system on tripod.
These base stations send a dense network of infrared laser beams into the room at millisecond intervals (these class 1 lasers are harmless to humans). The infrared beams strike the sensors, which are placed at different locations on the VR goggles. Based on the measurement data, the current position and movement of the glasses in space can be triangulated.
The VR glasses and the PC software continuously synchronize the movement data in real time. Thus, the real movement is converted virtually and you can walk through a computer world like through reality. Valve’s SteamVR tracking currently delivers the most reliable and accurate external tracking on up to 20 square meters. With SteamVR tracking version 2.0, even much larger tracking areas can be covered.
The advantage of external tracking is the comparatively high tracking accuracy and the size of the playing area. In addition, the stability of the tracking is very high. The biggest disadvantage of this tracking system is the relatively complex installation: The infrared transmitters have to be placed at certain points in the room and individually supplied with power. In addition, the system is difficult to take to other locations.
In this variant, the tracking is built directly into the VR goggles. External devices are not necessary. The tracking of the Oculus Quest 2, for example, is done via infrared cameras in the VR goggles that track the user’s position and movements relative to the environment. The VR goggles take care of all tasks themselves, which means that non-professionals can put the headset into operation quickly and easily at any location.
The biggest advantages of internal tracking are the ease of use and high mobility: An Oculus Quest, for example, can be used in almost any room and – if the lighting conditions are right – even outdoors. However, depending on the system, tracking dropouts can occur if the controllers are moved outside the camera’s field of view – behind the back, for example – or if it is very bright or too dark. However, developers are getting better and better at minimizing these dropouts, for example with AI-supported motion predictions.
VR Systems in comparison
If you want a high resolution, stable tracking and do not want to compromise on the graphics, you should go for wired VR headsets. For example, Valve’s Index or HP’s Reverb G2 can be mentioned here, which offer the highest-quality VR experience with the corresponding PC performance. However, the price is much higher because a powerful high-end PC is needed in addition to the professional VR headset.
Standalone headsets are much cheaper and mobile, but only specially developed experiences can be played on them and some compromises have to be made in terms of graphics and resolution. In the standalone sector, the Oculus Quest 2 is recommended due to the price-performance ratio. The price of these glasses is unrivaled because it is subsidized by the parent company Meta (Facebook). Standalone headsets can usually also be connected to a PC via cable or WLAN, so you can access higher computing and graphics power for the VR experience. A standalone is a great way to get started in the virtual world, and if needed, you can upgrade your VR setup later with a PC.
In this final graphic, we give a brief overview of some selected VR glasses available on the market, categorized according to the criteria mentioned in the article.
Further decision criteria for buying VR glasses can be found in the blog article “Quickly explained: The VR headset jungle“. And a more detailed explanation on the topic of tracking can be found on the website mixed.de: Virtual Reality: Everything you need to know about VR.
Categorization of VR-headsets (27.11.2021)
Titelbild: © Collage Pablo Dornhege – Photos by cottonbro and Michelangelo Buonarroti (Pexels)
Autors: Vincent Kaufmann, Pablo Dornhege, Franziska Ritter