VR is very cool but dizzy how broken

Editor’s Note: this article by the music and technology feeds, Web editing of Lei Feng did not change the intent of adjustment.

With the VR industry came into sight, VR early boom is in the outbreak. Domestic several VR field of cutting-edge businesses, China VR hardware is not low compared with international standards. If the “international standard” Oculus VR hardware, it could be said to be flat. For the majority of regular users is no doubt good news for domestic team of VR on the premise of maintaining hardware technically, high cost performance.

However, even the most sophisticated VR products, still has a fatal “mishap”: Dizzy feeling is too strong. Many VR experience that, over a period of time using the VR products, discomfort, nausea and even vomiting. This became the VR development one of the largest stumbling blocks, solve dizziness problems as the VR’s pressing problems.

One, why VR dizziness?

VR dizzy principle is very simple, because the eye sees (VR) images received from the ear (actually) does not match the information, leading to cerebral burden, resulting in a sense of dizziness.

There are two main aspects of this problem:


On one hand and 3D dizzy sense somewhat similar to 3D special effects blockbusters will make the audience feel dizzy, because outside of large numbers of actual Coke image, 3D movies, and rich defocus background image of an element. Moschino Galaxy Note 3 case

Picture elements are too rich, like distant defocus in the depth of the leaf is part of many elements. But when watching a 3D movie, the audience must abandon defocus images of these elements. Because these elements will make the eye focus again, and often failed to focus, it is easy to produce 3D dizzy, which is similar to eye in the snow snow blindness caused by long-term Visual focus cannot be searched.

Simply picture so realistic, so immersive you feel, your body thinks you are doing strenuous exercise, or a picture in the State, but in fact you are sitting on the seat did not campaign. This is a protective instinct, most people can exercise reduce dizziness, but one can’t really move at a distance.

Other VR hardware delay time sync, when man rotation angle or move when screen rendering speed to keep up, in VR, full view of the screen, and dizziness caused by such delay is the biggest problem, is currently the principal means to reduce latency is now weakened VR Vertigo. Moschino Samsung Galaxy case

-Reduce dizziness, delayed–VR field method

Purchase virtual reality devices, are an important indicator from the delay turns the head to rotate the picture.

But delay is to a large extent depends on the refresh rate of the display. The world’s most advanced virtual reality equipment refresh rate in 75Hz, including the famous Oculus DK2 and friends of music technology in Shanghai.

75Hz means that the render finish to display on the screen, you need at least 1 second divided by 75 equals 13.3 milliseconds at a time, including safety, time, generally a delay of 19.3ms. So any claimed delays in 19.3ms the following is false advertising.

Delayed 19.3ms is made up of what?

(19.3ms delay)

1, first of all from the head to read sensor data about 1ms of time, if we adopt the world class sensor, then the sampling rate in 1KHz, which means that can read up to 1000 data per second, then each data is 1ms, also reached the 1ms delay.

2, then the data needed by single chip computer and transmitted to a computer. Because their interface is different, just like air conditioning power plug not inserted into the small table lamp in, needed some conversion work, SCM is responsible for such conversion. Data from the sensor to the microcontroller about 1ms. Because the preceding data 1ms, so without these data to the microcontroller within 1ms, then data will be discarded.

3, followed by single-chip computer through a USB cable to transfer data to PC. USB cable has a very high rate of transmission, but entirely by the Host-side (that is, the PC-side) control transmission. In other words, if the Host does not receive data from single chip, then the data is discarded. HID cases, Host-side will often check for data transfer, and store the data into memory, so the time in 1ms. At this point, the data has reached the PC memory, covered all of the hardware. Restrictions such as the data bandwidth, communications protocol, takes up the time between 3ms~4ms, it’s hard to reduce.

4, after the transfer is complete in hardware, is the process of software algorithms.

Due to the analog signal noise and drift into digital signals, data exists in a lot of noise and drift. Complex digital signal processing method of noise and drift out. In this way, 9 axis data coming from the sensor becomes required for rendering game head rotation quaternion rotation data. This data is typically less than 1ms. When rendered as long as the rotation quaternion multiply the coordinates of the camera, view direction is obtained, can be used to render the scene. Through a special algorithm (for example, Time-warp, the fastest algorithm), according to previous data image, real display pictures. Thanks to the Time-warp algorithm, we can ignore the rendering delay.

5, when the scene needs to be done after the anti-distortion anti-dispersion process. These processes generally require GPU 0.5ms. For security reasons, this time set to 3ms, to ensure ready to transmit the next frame to the monitor, that is, before the next vertical sync signal to, GPU will be able to bring against the distortions and the dispersion.

6, and then transfer the image to the display of the time. As mentioned earlier, calculated in accordance with 75Hz, then you need 13.3ms. To this end already? No, the monitor also displays an image of the time. As the LCD monitor is crystal by the rotation of the electric field control of physical processes, ranging from traditional LCD display needs to 15~28ms time to respond. While the latest OLED technology would reduce this time to a microsecond.

Well, let them add up, 3ms + 3ms + 13.3ms = 19.3ms. This is the ideal situation, of course, also possible CPU performance, USB packet loss issues could lead to up to low latency.

Domestic and the “international standard” Oculus products are based on this algorithm, minimum delay is consistent, in the context of the world, 19.3ms delay is the most scientific, most credible delay calculation time.

Oculus looking forward delay can be reduced even further is not boasting. As can be seen from the above formula, the main bottlenecks in the 13.3ms on this delay. Through some special methods could be reduced by half, or even less. But this requires joint efforts of hardware manufacturers, operating systems, game developers.

Currently, VR hardware to improve latency is improving Vertigo the best solution, all the time you need the compression to lower picture delay, from the hardware to address the problem of dizziness. Secondly like 3D Vertigo as before, users through a period of adaptation, to make VR real virtual reality product.


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Originally published at folkartsblog.wordpress.com on December 15, 2015.