World Scale: Cameras vs. Your Head
One of Virtual Reality’s main features is the immersion, which is hard to achieve when things don’t quite “look right”. With so many different devices to watch videos on, and so many different heads watching them, things aren’t always going to be correct before you make some adjustments. Here are the major things you can set in many of the popular players that will help you tweak your VR experience.
Inter-pupillary Distance (IPD)
The distance between the center of your pupils, IPD, is probably the biggest factor in VR looking correct. It’s also a technical hurdle in building a camera setup, as most high quality cameras are just too big to get the centers of two lenses as close together as your eyes. The male average is about 65mm (2.55 inches), while around 70% of the population is between 61 and 69mm, but it ranges from the low fifties to the high seventies (about one inch).
If your IPD is lower than the camera’s, then everything tends to look too small in VR, and if your IPD is higher than the camera’s then things look too big. Unfortunately this distance is fixed when the scene is shot, and can not be adjusted very much with software without warping or seriously lowering the quality in other ways.
Many playback apps will let you adjust playback IPD, also known as Stereo Separation. The primary function of this is to solve double-vision problems and your eyes straining to be able to focus on things. Once you’ve found the setting where you can comfortably focus and see a single image, you probably won’t be able to adjust it much more than a few millimeters from that point before you bring back the double-vision. Making small adjustments towards what the camera setup used, as long as they don’t cause eye strain, can help make the world-scale seem more realistic. We strongly recommend adjusting this setting where available, even if you do not have any issues with the way the scenes look, as it will greatly decrease the amount of strain on your eyes.
60fps scenes are shot using an IPD very close to the male average. Our older scenes were shot with a setup that had the IPD too high, which is the main cause of the world scale issue in those scenes. Our new setup is designed to give as close to a realistic scale as possible for as wide a range of our audience as we can reach.
Zoom / Render Distance
Zoom is simply how big or how small to display an image in your headset. In VR, however, it can get pretty weird as your brain tries to correct things that don’t quite make sense. This is why if you attempt to fix a small world scale by just zooming in, it can make you feel like your head is in the wrong place when you look straight ahead, and can be disorienting when you look around. Small adjustments, though, can help everything look more realistic.
Distance is how far in front of you the 3D focal point is placed. It has a visual effect similar to zoom but is more complex in how it’s rendering the change. Some players will have both available to adjust, and the difference between the two is usually most apparent in the menus that you adjust them from. Because it is a properly rendered change, changes to distance are less likely to cause disorientation when you look around, but more likely to make you feel like your head is in the wrong place when watching a POV scene. Like zoom, large changes should be avoided, but small tweaks can help you feel like you are placed properly in the virtual space and objects are the correct distance away.
In players that allow changing both zoom and render distance, the two settings can be combined to better adjust world scale. For example, if what you are looking at seems too small, you can zoom in to fix the general size, and then move the distance further away to correct where your head should be. This combination can be a little disorienting though, and may cause some distances to look worse, or motion sickness when looking around.
Field Of View (FOV)
Our VR scenes are filmed and meant to be viewed with a 180-degree FOV. In some players, or for some people with glasses it can be more comfortable to make slight adjustments. Adjusting it too much will make everything appear stretched.
Horizontal FOV is the most common to adjust, but some players may also have vertical. Increasing both horizontal and vertical FOV by the same amount will have an effect similar to zooming in if you’re looking straight forward, but will warp in different ways near the edges.
Some players use FOV to refer the just what is visible on the screen, so the number will be much smaller than 180. You can use the player’s default setting as a starting point, but the adjustments should work the same.
In Short
If your IPD is too far from the one the cameras used when shooting, then you’re going to have a tough time getting world-scale to look correct without impacting the quality of the experience in other ways. Small adjustments to zoom, distance, stereo separation, and FOV can all help, but can also introduce other issues if adjusted too much. You can adjust things a bit more if you are planning to mostly look forward, as most problems come up when you look near the edges.
Part of how things look to you is also subjective, so the numbers given here may not exactly line up with your perception. Adjusting settings up or down should have the same effects, but try to trust how it looks to you rather than the raw numbers.