VR glossary

We are going to be hearing about VR more and more, and with new technology comes new vocabulary. There’s a lot to learn, so let’s get started!

Presence: The feeling that what you are seeing is real, and you are in that reality. It’s a feeling of “being there”.

Field of view: The height and width of your vision. Basically how much you can see around you.

Near Field: Objects close to you are said to be in the Near Field. Because of the way vision works, the closer the object, the more three dimensional it appears.

Far Field: Objects far enough away that they don’t need to be as visibly detailed as objects close to the subject.

Mid Field: Objects that are close enough that they need to be detailed, but far enough away that stereo vision has minimal effect. These objects don’t have to be as detailed as objects in the near field, but more then far field objects.

HMD (Head Mounted Display): This is the part that you put on your head. It contains two separate screens, one for each eye, with each having a lease in front of it that provides magnification and focus.

Latency: This is the amount of time it takes for information to travel out and back. In VR, high latency can cause a delay between head movement and what is displayed on the screen, which can cause nausea in many people.

Resolution: How many pixels make up the image. Usually described by width and height, such as 1920×1080, which means the screen has 1,920 pixels going across its width, and 1,080 going up and down.

Pixel Density: This is a ratio of how many pixels a screen has in a square inch. Usually abbreviated as PPI, for Pixels Per Inch. Two screens can have the same resolution, but drastically different pixel densities. For instance, a 21” computer monitor and a 50” TV can both have a resolution of 1920×1080, but the pixels on the 25” screen are packed much closer together, and are frequently smaller. This results in a clearer image because the blocks of color are closer together. 

Refresh Rate: How frequently the image is replaced on the screen. In VR, a high refresh rate is very important because the image has to be updated frequently, otherwise the human brain becomes uncomfortable and becomes disoriented or nauseous. 

Screen Door Effect: When the images on the screen are magnified like they are in VR, somethings it is possible to see the individual pixels. This gives the effect of looking though a screen door, where there are small out of focus lines in your vision. The higher resolution the screens are, the less noticeable this effect is.

Frame Rate: Frame Rate is the number of times a brand new image is displayed on the screen per second (also known as Frames per Second, or FPS). This is reason this is important for VR is because a low frame rate will cause nausea, due to the delay between what the brain expect to see as the head moves, and what the eyes are seeing. A high frame rate also means smoother movement. For VR to not cause nausea and headaches, the sweet spot seems to be 90-120 FPS. Because the image is being split up, with alternating images for each eye, that means each eye is going to see 45-60 FPS. Any lower and we run into problems.

Room Scale: Room scale refers to a VR experience where you can walk around. Some headsets work better for this then others right now, although updates are coming fast. Right now the HTC Vive is the goto room scale experience to have. Games like Budget Cuts allow you to move around a building, taking out robot security guards in a quest to steal your termination papers. It’s more immersive, but can cause discomfort in some people. 


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