Why do people get headaches and nausea when playing 3D games?

Patient's question:

Main symptoms: Headache
Onset time: While playing CF
Laboratory test results: Not checked

Doctor's answer:

Symptom Analysis: It can be temporarily referred to as "3D Syndrome," where frequent movement of 3D images causes dizziness and a sense of nausea. However, this requires a prior history of playing a 3D game for an extended, uninterrupted period.
Advice: First-person perspective 3D games like World of Warcraft (WOW) and Counter-Strike (CS) may cause this sensation if played continuously for a long time. However, it varies from person to person—most people do not experience it, only a few, including myself, are affected. For example, I can't play CS continuously for more than 6 hours without issues. During the open beta of WOW, I once played for dozens of hours straight, which led to one night where I felt terrible—dizziness, nausea, stomach pain, discomfort in the stomach and stomachache, followed by headaches and coughing. Additionally, hunger may exacerbate this reaction.
Lifestyle Care: Dizziness and nausea while playing 3D games are similar to the causes of motion sickness and seasickness. Below, I will explain the reasons:
Humans obtain information about the external environment through hearing, vision, and touch. Over long-term evolution, our sensory organs have become highly coordinated. For example, the inner ear contains an organ called the "vestibular apparatus," which senses the body's balance, such as movement direction and acceleration. The eyes also have specialized nerves to detect motion. These motion-sensing organs are very sensitive, transmitting the detected motion information to the central nervous system, which then controls the body to respond appropriately to the effects of motion.
When the perceived motion amplitude or frequency exceeds a certain threshold, the central nervous system may cause discomfort, such as dizziness and nausea, objectively preventing the current motion from continuing. This is actually a self-protection mechanism, as large-scale, high-frequency motion can potentially harm the body. Over long-term evolution, this fact has been encoded into human DNA. However, the intensity of this self-protection mechanism varies significantly among individuals. Some are more sensitive, like those prone to motion sickness, while others are less sensitive, like those who are not easily affected by motion sickness.
Another possible cause of motion-induced dizziness is that when the motion frequency is too high, the sensory organs for motion detection do not respond at the same speed. This leads to differences or even contradictions in the motion signals sent to the central nervous system. As a result, the central nervous system becomes confused, unsure which signal to trust, and may issue dizziness signals to make the body feel uncomfortable, thereby slowing down or stopping the motion.
In summary, the reasons for dizziness and nausea while playing CS are roughly as follows: The visual nerves perceive large-scale, high-frequency motion. Normally, if the CS graphics were less realistic, the central nervous system would automatically identify the motion as fake and suppress the neural impulses from the visual system. However, because the graphics are realistic, the central nervous system believes it is real, while other motion-sensing organs (such as the vestibular apparatus) do not detect any motion. This creates a highly contradictory and unpredictable situation for the central nervous system, leading it to strongly issue dizziness signals, hoping the body will stop to escape this unfavorable scenario.