So I'm currently learning about Virtual Reality (VR) in Coursera (https://coursera.org/specializations/virtual-reality), and I thought I would share some of the most relevant lessons that I'm learning. In this post, I will talk about the so-called 3 illusions of VR. These illusions, combined, allow us to feel present in the VR experience, and consist of the following:
- Place Illusion: this illusion refers to the feeling that the user has of being somewhere else. This virtual place may be a realistic place or a fanstasy place. In both cases, if the user feels transported to this other location, place illusion has been successful.
In VR, this is achieved with the interactive rendering of the scene (e.g., if the user rotates the head, the scene will be shown accordingly) and high-quality graphics. Obviously, the different degrees of freedom (https://xinreality.com/wiki/Degrees_of_freedom) of the different types of Head Mounted Displays (HMDs) allow different levels of place illusion (e.g., mobile VR HMDs support head rotation, but not head tracking). Moreover, HMDs allow the user to isolate visually from the environment, in contrast to a common screen, eliminating any distractions from the surroundings.
- Plausibility Illusion: this illusion refers to how much the user believes that the events happening in the virtual scenario are actually occurring (despite knowing the he or she is in a virtual place).
This illusion may be broken if those events do not seem realistic or natural. For instance, let's assume a scene that is shared between the user and other virtual characters. If the user interacted with them and the virtual characters did not respond at all (as if the user was a "ghost"), this would not be considered a realistic event and hence plausibility illusion would be broken. It is possible to enhance plausibility illusion by designing interactive behaviours in the scene (e.g., you cross a street and cars stop to allow you to cross it).
An important difference between place illusion and plausibility illusion is how they can be broken and recovered. In the case of place illusion, considering that it refers to our feeling of the realism of a place, it is a perceptual illusion. This illusion may be broken, for instance, if the graphics are not good enough (pixelated areas). However, this illusion may be recovered as soon as we look around and see other parts of the scene that have been properly rendered (or not pixelated). In contrast, in the case of plausibility illusion, it is a cognitive illusion, considering that it refers to our feeling of the realism of an event. If we see a virtual character that shows non-natural behaviour (e.g., repetitive movement patterns), it becomes hard to believe again in the realism of the events after we turn around.
- Embodiment Illusion: this illusion refers to the feeling that user has of being in a different (virtual) body. This is usually achieved by placing appropriately an avatar under the camera and displaying it after the user rotates the head downwards. Just like with place illusion, it is possible to achieve different levels of embodiment illusion, depending on the degrees of freedom that the HMD offers. For instance, a high-end HMD may offer hand tracking with the use of controllers, allowing us to control the arms of the avatar and, therefore, feeling that we have more control of the virtual body. In contrast, mobile VR HMDs do not offer this possibility and, therefore, allow a lower level of embodiment illusion.
This is just my first post on VR, but I expect to keep writing more while I keep learning. :)