Archive notice: This article was originally published on March 20, 2019. Links and embedded videos are preserved as part of the historical record.
Another aspect is haptic perception. In conventional VR games, this is often limited to the functionality of traditional game controllers. It would be desirable to allow the user to explore the visually perceived virtual environment haptically by touching virtual objects or physically interacting with them. The central questions addressed in the study on “Saltar VR” are:
- Which game mechanics are relevant for VR platform games?
- How much movement is even possible in a VR platform game?
- How can elements of VR be made tangible for the player?
Using a human-centred design approach, a total of 17 different game mechanics were implemented and combined and strung together in ten stations of increasing difficulty. During the investigation, two topics emerged as particularly relevant: passive haptics and movement in VR.
Passive haptics
Passive haptics is a simple and cost-effective way of enabling haptic perception in VR. Here, a real object is used for which a virtual equivalent is created in VR that corresponds to the dimensions, texture or other properties of the real object. Ideally, it is therefore a one-to-one replica of the real object. If these objects are to be moved, for example by lifting them, additional tracking is required in order to adequately represent the position and orientation of the real object in the virtual world. Studies have shown that passive haptics increase presence (i.e. the feeling of actually being present in a virtual world), improve orientation in virtual space and increase training performance.
The first passive haptic in “Saltar VR” is a 3D-printed lock, whereby the front part of an HTC Vive controller acts as a counterpart and can therefore be used like a key. When the player turns the controller (key) in the passive haptic (lock), a process is initiated that is a prerequisite for mastering the station. The next haptic element is a wooden board. This lies at a certain position on the floor in the tracking area and is intended to give the player the impression of actually walking across a narrow bridge. The last passive haptic is a movable box whose position is tracked by the VR system so that its virtual image moves with the player as they move.
Locomotion
One of the biggest challenges in the design and implementation of “Saltar VR” was the realisation of continuous movement, which is an important feature of a platform game. It had to be ensured that the player is never limited by the playing area and that all areas in the virtual world that need to be actively played in are accessible at all times. Several types of locomotion were used for this purpose. Standard locomotion is mainly based on real walking technology. The player’s physical movements are transferred one-to-one into the virtual world, allowing them to run, jump, crawl or duck by performing the same movements that the player is familiar with from the real world. The player has an area of 4 x 4 metres at their disposal. At the end of each station is a portal that transports the player to the next station when they pass through. The player can also use a beam cube or move across moving platforms. A beam cube can be created and thrown using a controller. The player then teleports to the position of the stationary beam cube by pressing a button.
As the player moves through the stations, they must be careful not to fall off the platforms. The conditions under which the player falls are implemented as closely as possible to reality. Additional HTC Vive trackers have been attached to the player’s feet and, based on the position of the feet, their movement and the position of the head, conditions have been defined that lead to the player falling off a platform in the game. This activates Unity’s physics engine and thus simulates free fall. The HTC Vive trackers also enable a representation of the feet, which supports the feeling for one’s own body and helps the player to place their steps in the right position.
Results
An evaluation revealed that passive haptics, provided there are no discrepancies (between the real object and its virtual counterpart) and the player is prepared for them, lead to an increase in presence. At the same time, various aspects of passive haptics are identified that influence the player’s sense of presence. This includes the use of passive haptics to which the player’s body reacts. The wooden board in combination with virtual height fulfilled this requirement and increased the player’s presence. The movable box also had a positive effect due to its mobility and the associated large radius of action as well as its manipulation via the hands. A reduction in presence occurred above all when discrepancies were present.
Overall, it was shown that the final prototype is a positive experience and generates joy of play. The developed game mechanics were largely rated positively. Based on this, a list of individual and combined game mechanics was created that could also be used in the context of a VR platform game in the future. In particular, the game mechanics of dodging in various combinations with moving platforms, appearing or disappearing platforms and jumping over platforms should be emphasised positively. A representation of the feet seems indispensable for this. Smaller puzzles, such as memorising platforms that can be walked on, also challenge the player’s mental abilities and add variety to the game.
In general, it can be assumed that the basic elements and mechanics of a two-dimensional platform game can largely be transferred to a VR platform game. Balancing over a bridge (wooden board as passive haptics) at great heights proved to be particularly suitable for a VR platform game. The three-dimensional representation allows the player to experience the height in VR in a special way. The beam cube proved to be an exciting alternative to the teleportation that is common in the majority of VR games, which includes the additional mechanic of throwing and thus forms a form of locomotion that in its entirety represents a game mechanic of its own and offers the player a further challenge.
One starting point for future research is the size of the required playing area: a minimum size of 4 x 4 metres makes it difficult to establish the game in the consumer sector. A dynamic approach that allows the game to be played on different sizes of playing surface could provide a remedy. Since a platform game in VR is based on the representation of the body and the transmission of the player’s physical movement, the attempt at more precise tracking could be a further starting point for subsequent studies, which could refine the falling behaviour and improve the detection of collisions with obstacles.
