1. Your brain recreates the 3D environment from physical objects and is "trained" to certain distances and movement, etc. When you use 3D glasses, either movie or VR, the "stereo" effects are anything but natural. There's a lot of stuff flying around at "non-natural" distances, especially near you. The effects are exagerated otherwise at some point you will "stop noticing it's 3d unless you pay attention". The exagerations are compensated by your brain and also causes eyestrain. Look at a pen, closer, closer, at some point you see 2 pens, now do that back and forth for 30 minutes, You will have the same pain.
2. Perceived movement vs. internal ear and balancing your body. VR is awesome at screwing everything up. I love VR but can't stand it for a long period because of that. Your brain expect you falling, or this thing comming at you to hit, you walking should have some motor feedback, driving too. Nope. No G's, no wind, no nothing. To put it in simple terms... brain tilts
I had problems playing Quake on a 2D screen. It went out with intense exposure. I would do 30 minutes, get sick, start the next day, eventually I've managed to pull out 12 hours in a row. Life was fun and simple back then ;). I don't have that luxury anymore for VR but I'm sure it would be the same process to desensitise through gradual increased exposure.
1. Your brain recreates the 3D environment from physical objects and is "trained" to certain distances and movement, etc. When you use 3D glasses, either movie or VR, the "stereo" effects are anything but natural. There's a lot of stuff flying around at "non-natural" distances, especially near you. The effects are exagerated otherwise at some point you will "stop noticing it's 3d unless you pay attention". The exagerations are compensated by your brain and also causes eyestrain. Look at a pen, closer, closer, at some point you see 2 pens, now do that back and forth for 30 minutes, You will have the same pain.
2. Perceived movement vs. internal ear and balancing your body. VR is awesome at screwing everything up. I love VR but can't stand it for a long period because of that. Your brain expect you falling, or this thing comming at you to hit, you walking should have some motor feedback, driving too. Nope. No G's, no wind, no nothing. To put it in simple terms... brain tilts
you can look up a lot of stuff about this on the internet with VR sickness, motion or 3D sickness... lots of articles, i.e. https://en.wikipedia.org/wiki/Virtual_reality_sickness
I had problems playing Quake on a 2D screen. It went out with intense exposure. I would do 30 minutes, get sick, start the next day, eventually I've managed to pull out 12 hours in a row. Life was fun and simple back then ;). I don't have that luxury anymore for VR but I'm sure it would be the same process to desensitise through gradual increased exposure.