Carl Callewaert, head of evangelism at Unity Technologies, told at Unite Europe 2016 how to make a VR game not cause seasickness in users.
The main difficulty with VR projects is that the user can literally start to feel sick. One way to avoid this, says Callevert, is to remember about the physiology of human eyes. We have binocular vision. This means that the eyes get a slightly different picture each. If the information is very different, then the person will start to feel sick.
At the same time, Kallevert notes, partly due to the fact that the information is different, the human brain is aware of the volume of things. VR images face a difficult task: you need to simultaneously get a sufficiently voluminous picture and not make the player feel sick because of too much difference in images. In addition, you need to give the player an idea of the characteristics of the surrounding world – the distance to objects, their height, and so on. To do this , Callevert suggests relying on several basic principles:
1) use the laws of perspective;
2) apply lighting and shadows correctly;
3) remember that the brain determines the size of things by comparing them with each other.
To remember the laws of perspective means to understand that even if the picture is flat, lighter and dimmer objects are always perceived by the human brain as more distant.
The picture shows two satellites of Saturn – Epimetheus (left) and Janus (right). Due to the fact that Janus is brighter and better lit, it seems that he is closer to the observer. In fact, he is further away
In addition, if we see lines converging to a point, then the figures that are closer to the point of convergence are perceived as more distant. This should also be used in creating a picture for VR.
With the help of shadows, the brain also gets an idea of the volume. To illustrate this principle, Callevert gives this example: if we see smooth columns, we can hardly understand where the shadow ends and the column begins.
But when a column consists of faces, the brain easily understands the volume.
The third principle of Callevert means that if you need to let the player understand how big an object is, you need to place some familiar detail next to it, which the brain can easily identify. For example, in the image below, we can see that the bush is quite large. Understanding is achieved due to the fact that we compare it with the tree next to which it grows.
To understand whether it was possible to create a volume or not, Callevert advises closing one eye. If depth and volume are not perceived by one eye, then the image is not suitable for VR.
