While Monument Valley and Superliminal have shown that it is interesting to use optical illusions in the video games, little is known about how to make the next games with illusions. Therefore, we propose a workflow and provide an illusion database and 6 specific illusion editors to help game designers without illusion expertise to build the illusion games.
This is our workflow. It consists of 5 steps: (1) choosing an object, (2): searching for an illusion with our database, (3): selecting a mechanic, (4): integrating the illusion into the game, (5): and optional revealing the illusion.
I will use NS-Shaft as an example to elaborate how to use our workflow to apply an illusion.
Step 1: Choosing an object
To apply illusions, we have to choose an object from the game.There are many objects to choose from, such as the platforms, the character, the remaining life, and so on. Different objects result in different candidate illusions later. Here, let’s choose the platform.
Step 2: Searching for an illusion with database
We look for matching illusions from our illusion database based on the object. Our database contains 163 illusions in total.
Here is the link of our database: http://hci.csie.ntu.edu.tw/illusiondb
Our database provides two meta-level tags: visual elements and effects. By selecting these tags, we can find corresponding illusions. The visual element tags describe what the game object looks like, while the effect tags describe what kind of effect the user wants to achieve.
In this example, we search related illusions from visual elements. Let’s observe the standing platform. It is rectangle, and parallel to each other, so how about we choose the tags rectangle and parallel.
Our database then returns a list of related illusions. Each contains a short animation and its name. We can click the illusion for more info such as a short description and related tags. In this example, we pick the Zollner Illusion. The Zollner Illusion makes parallel lines seem askew.
Step 3: Selecting a mechanic
After picking the illusion, now we have to think about how to apply the illusion to our game. We propose 2 illusion mechanics to think about, Misleading and Swapping realities.
Misleading
Misleading increases the game’s difficulty. To mislead players, we put both objects with and without illusions into the game. In this example, since the Zollner illusion makes the platforms seem tilted, we can put both the illusionized platforms and the real tilted platforms into the game. Now players are hard to distinguish whether the platforms are indeed tilted or not.
Swapping Reality
On the other hand, Swapping realities creates different gameplay. To swap realities, players need to turn illusions into the reality of their games. In this example, we disable the player’s movement and allow players to add stripes to the platforms to make the platform look tilted, making the character slide from the platform to reach the goal. By doing this, illusion becomes reality.
Also, this can be done in a reversed way. Players remove the stripes by themselves to bring the reality back.
These two mechanics lead to different designs of illusion games. In this example, we take the misleading one.
Step 4: Integrating the illusion into the game
Before this step, we have a game design with illusion. Now we have to implement it.
To help game designers, we provide 6 specific illusion editors for rapid prototyping.
Our illusion editors integrate prior knowledge about illusions and help developers to apply illusions to their game objects.
Illusion editors: https://github.com/PoYaoCosmosWang/Game-Illusionization
To use our illusion editors, just simply download and import our Unity Package from the link above, and then assign the game object to add illusion. For more details, please refer to readme in each illusion editor.
Step 5: optional revealing the illusion
Lastly, we have suggestions for designers to reveal illusions. Revealing explicitly makes players realize that there are illusions, rather than just glitches or bugs. However, some designers do not reveal illusions because they want to use illusions as Easter eggs for players to find out. So, we leave this step optional in our workflow.
There are three ways to reveal: Adding an indicator, changing perspective, and removing the interference. We have more details about these in our paper. In this example, let’s choose removing the interference.
By removing the interference from the platforms, we can see if the platforms are really tilted or not.
After our workflow, the classic mini game has been illusionized to puzzle players and increase its difficulty.
In this project, we also presented (1) other illusion game examples, (2) illusion game evaluation to have a preliminary understanding of illusion games, (3) workflow evaluation to understand how our workflow helps game designers, and (4) in-depth interview to know how the remaining workflow, especially our illusion editors, facilitates the implementation of illusion games.
In conclusion, we propose a workflow to integrate optical illusions into video games.We provide an illusion database and 6 illusion editors.With our work, we hope more game designers without illusion expertise to join us to create more illusion games.