Movement to Photon, the Presence in Virtual Reality

Virtual reality is a medium in itself with its own rules, and one of them is telepresence : the feeling created by finding ourselves in the remote place shown by our virtual reality glasses. We explain what photon movement consists of, the objective that all virtual reality systems pursue and what are the hardware requirements to achieve it.

Presence is the ultimate goal of virtual reality , it is its philosopher’s stone, its holy grail and therefore what is tried to be achieved in any environment based on VR since without it then it ceases to make sense.

Movement to Photon

It consists in making the spectator’s brain believe that he or she is really in the virtual world , in suspending the sensation of disbelief of the user and that therefore he or she acts unconsciously as if they were present in that virtual world.

The photon movement of Virtual Reality

tiempo de fotón

The key is the motion-by-photon concept: the time it takes to perform an action in the virtual world until the result reaches our eyes, and that time to overcome the effect of disbelief for the entire process is less than 20 milliseconds . We are not talking about rendering the frame in less than 20 ms, but rather that the entire process takes less than that time:

  • The user makes a movement or presses a button.
  • The system reads the user action and interprets it.
  • From the interpreted input information the system generates a new frame.
  • The frame is sent to the virtual reality unit.
  • The VR headset updates the image and displays it to the player.

All this process has to be done in the shortest time possible and never break the imposed limit, which is why new systems always seek to carry out the entire movement-to-photon process in an increasingly lower time.

Additional limitations to obtaining presence

abismo vr

It must be understood that there are a series of added latencies that we cannot control, such as the speed at which the data is transmitted from the motion sensors and the controller or the sending of the image from the system to the reality helmet screen. virtual.

This is the reason why, for example, we have not yet seen wireless virtual reality systems with connectivity for PCs and consoles, due to the fact that the latency in sending the data would make the screen take too long to arrive and be processed. .

This is the reason why the only way to generate presence is by having extremely powerful hardware, which cuts the photon time as much as possible and the process can be carried out in less than the stipulated time. For this, screens with a high refresh rate are used, with speeds much higher than 90 Hz.

The relationship between high-frequency displays and virtual reality

frecuencia imagenes

The appearance of high-frequency panels in the PC world has as its origin the use of high-frequency LCD panels to function properly. The need for the process to take less than 20 milliseconds is what has caused these panels to appear, which could then be used in gaming monitors.

This also means that there are two competing trends, the first one seeking the highest possible resolution and image quality, the other trying to achieve the highest possible speed. One is in competition with the other, but it also creates a number of additional problems such as the fact that a higher resolution is required in virtual reality glasses than in a normal environment.

But the preference, the problem to be solved initially is the speed and the appearance of the high-frequency panels has made many old games are adapting to work at a high rate of frames per second.