Developing a Virtual Reality Video Game to Simulate Rip Currents

All methods used were approved by the Hofstra University Institutional Research Board (IRB). The VR video game developed was used to survey 64 individuals.

NOTE: Scripts were written in the C# language, and are available for download at: https://github.com/Jasebern/HofstraVR.

1. Creation of VR rip current video game: Virtual environment and user input/output

1. Open VR development platform (e.g., Unity¹⁸). This procedure was completed in Unity 2018.3.1f1.
   1. Start a new 3D project entitled ‘Rip Current.’ A 3D project contains one or multiple scenes comprising of ‘game objects’ that can appear as solid objects¹⁹. Scripts can be added to game objects allowing for interactivity and real time changes to the environment. This project will contain four scenes and numerous game objects.
   2. Open the Unity Asset Store tab. This contains ‘prefabs’– already-created collections of 2D and 3D game objects and audio files — developed by other users that can be added to the project²⁰.
   3. Import the ‘Oculus Integration’ asset from the Unity Asset Store that provides foundational assets for VR development.
2. Create the first new scene: Main Menu (Figure 1).
   1. Use Assets | Create | Terrain Layer and then add appropriate coloring to create a hilly green terrain asset as an appealing background for the main menu scene.
   2. Use GameObject | UI | Canvas to add a new canvas, entitled Main Menu, with a text box for the title VR Simulation. A canvas is a game object that stores text and buttons allowing user interaction and specified events in the simulation based on that input⁴.
   3. Attach scripts, written in the C# language, to a game object. Add the script by selecting the desired target game object in the scene hierarchy. Then, in the Inspector tab, select Add Component | New script, and enter the desired script title.
   4. Follow the above procedure to add the script entitled MainMenu to the Main Menu canvas.
      NOTE: Please see Table 1 for title and function of all scripts used.
   5. Use GameObject | UI | Button to add four text buttons to the canvas: Start, Options, JoVEについて, and Quit. Call appropriate function from MainMenu and MouseHover scripts when a button is selected.
3. Create the second new scene: Buoy Test (Figure 2).
   1. Download the Realistic Water asset from the Unity Asset Store and add the Sea prefab to the scene.
      1. Add an audio file of ocean waves to the Sea prefab on loop. Add from the Inspector tab by selecting Add Component | Audio Source.
   2. Use the terrain layer tool as above to create a Game Object named Beach. In the Terrain options in the Inspector tab, use the Paint Terrain and Terrain Settings tool to style and color as sand.
   3. Download the Standard Assets package from the Unity Asset Store and add the Player prefab to the scene. The Player prefab includes a Camera that is embedded within the Player, thus following its movements to create the sensation that the game participant is controlling the Player.
      1. As performed above, add the PlayerController, PlayerMotor, PlayerMotor2, and FloatObject scripts to the Player prefab. Those scripts allow the game participant to control the Player prefab by using Oculus VR Controllers.
      2. Add an animation to the Camera by selecting Assets | Create | Animator Controller. Use the Animator Window to record an animation of the Camera bobbing up and down and set it to loop continuously. This simulates a person keeping afloat in the ocean.
      3. As performed above, add a Canvas entitled TextCanvas. Child TextCanvas to the Player by dragging it into Player in the hierarchy. A child game object inherits the movement and rotation properties of the parent game object. Add the text “Swim through the buoys” to TextCanvas. Record an audio file reading that text, add it to TextCanvas as performed above, and set it to play at the start of the scene.
      4. Set the player location by navigating to the inspector tab and adjusting the 役職 in the Transform options. Set player location to X=-23.44, Y=1, and Z=5.97.
   4. Download the VR Hands and FP Arms Pack from the Unity Asset Store and as above child the ‘FP_Character’ prefab to the Player. This will allow the arms to move with the Player and also bob up and down with the Player Camera.
      1. Choose the desired prefab by selecting it in the hierarchy and checking the box next to its name. The FP_Character prefab contains both male and female prefabs, each containing two arms, left and right.
   5. Add a new Game Object by right clicking in the Hierarchy and selecting Create Empty. Name the Game Object Checkpoint.
   6. Download the Simple Buoy asset from Unity Asset Store and add the Buoy prefab to the scene as a child of the Checkpoint. Duplicate the Buoy prefab by right clicking on it and selecting Duplicate. Name one ‘buoy L’ and the other ‘buoy R,’ and place them 4 units part in the X axis by adjusting the transform position of each as above. Set the location for buoy L at X=-2, Y=0, and Z=0, and location for buoy R at X=2, Y=0, Z=0.
      1. In the Inspector tab for the Checkpoint Game Object, select Add Component | Physics | Box Collidor. Then, select Edit Collider and draw the collider between the two buoys.
      2. As above, add the Checkmark script to the Checkpoint Game Object. The script exits the scene once the Player enters it (i.e., swims through the buoys) and transitions to the next scene.
4. Create the third new scene: Wave Test (Figure 3) by selecting File | Save As while still in the Buoy Test scene and renaming it.
   1. Delete the Checkpoint Game Object by right clicking on it in the Hierarchy and selecting Delete.
   2. Add a simple wooden boat to the scene by downloading the Old Wooden Row Boat v2 asset from the Unity Asset Store and add the Boat prefab to the scene. Adjust the Transform position of the boat as above to X=-12, Y=-0.16, and Z=14.66.
   3. Download the Low Poly Animated People asset from the Unity Asset Store and add the Kid prefab to the scene. Duplicate the Kid prefab as above and child both to the Boat prefab, renaming the Game Object に Boat with kids, and locating the two kids on top of the two seats in the boat.
   4. As above, add an Animator to the Boat with kids Game Object, and record an animation of the boat slowly circling around the water, emulating a rowboat slowly moving around.
   5. Navigate to the Player prefab and its children in the Hierarchy window and rename the left hand to ‘wave hand.’
      1. As above, add an Animator to the wave hand and record an animation of the arm and hand moving up and down simulating a hand wave.
      2. As above, in the Inspector tab for the Player Game Object, add an Audio Source with an audio clip of a hand splashing in water, distinct from the clip of two arms splashing in the water added earlier.
      3. As above, add the FemaleAnimate script to the wave hand, to allow the game participant to control the hand wave using the Oculus Controllers.
   6. Adjust the text in TextCanvas to read ‘Wave to the people on the boat!,’ record an audio file reading that text, and set it to play at the start of the scene.
   7. Based on the PlayerMotor2 script, as soon as the participant sees the boat and waves, Unity transitions to the Rip Current scene.
5. Create the fourth new scene: Rip Current (Figure 4).
   1. Adjust the text in TextCanvas to read ‘You are being pulled from shore!’ and as above, record an audio file reading that text, add it to TextCanvas, and set it to play at the start of the scene.
      NOTE: Do not explicitly state that the participant is experiencing a rip current, in order to most accurately simulate being unexpectedly caught in a rip current. 
   2. As above, create a new Game Object in the hierarchy named rip_collider and add a Box Collider. To use rip_collider to emulate a rip current as a narrow channel of flow extending from the beach into the ocean, use transform to set the position to X, =251, Y=1, Z=251, and change the scale to X=8.2 and Z=35.7 to create appropriate dimensions. The PlayerMotor2 script also simulates a rip current by constantly pulling the Player perpendicular (away) from shore (i.e., beach terrain). This rip current is a constant force 1.25 times stronger than the normal player swimming motions.
      1. Select GameObject | Effects | Particle System to add a new particle system, entitled ‘Rain Basic,’ and child it to rip_collider. A particle system emulates liquid entities in 3D such as rain and clouds. The particle system is used to simulate foamy water, which helps demarcate a rip current in ocean water. To do so, in the Inspector tab set the transform position to X=0, Y=3, and Z=0.97, and scale X=0.1 and Z=0.1, in order to embed the particles within the rip current channel.
   3. As above, use the Inspector tab to add the RipExit script to the rip_collider Game Object. The script records whether the Player escapes the Rip Current (i.e., exits the rip_collider collider).
      NOTE: As described in Table 1, the PlayerMotor2 script controls most aspects of the Rip Current scene, by exiting the scene and returning back to the Main Menu scene once any of the following conditions is met:
      — Player waves
      — Player exits rip_collider
      — Stamina reaches zero
      The script also writes out the results of player interaction in the scene to a file, used for later data analysis on overall participant interactions with the rip current.
6. To build the final project, select File | Build Settings and ensure all four scenes created are checked off and in the proper order. Then, select the platform PC, Mac & Linux Standalone and select Build. This will prompt a selection window for a build output folder. Select a suitable folder (i.e., ‘Desktop’) and then build. This will create an executable file shortcut in the desired folder entitled ‘Rip Current.’

2. Survey individuals with the VR rip current video game

1. Open up the ‘Oculus’ software using the desktop shortcut, and then set up the hardware through the program. Ensure that the headset, two sensors, and two controllers are all showing as green (Figure 5).
   1. Determine a survey location and recruitment method. In this study, convenience sampling was employed. The researchers visited a public beach two times per week for eight weeks during July and August and solicited potential participants while they walked along the beach promenade. Besides being at least 16 years of age, there was no other requirement besides willingness to participate.
2. Administer survey part one (consent form and demographic questions) on a separate iPad.
3. Hand the VR controllers to the participant and make sure they are holding them properly in the correct hands, and are familiar/comfortable with the controls, and then fit the headset on the participant.
4. Select and run the Rip Current shortcut from the Desktop.
5. Allow the participant to proceed through the simulation, providing coaching/advice only when necessary. They should complete the main rip current scene on their own.
6. Once they finish, remove the headset and begin part two of the survey, the interview portion.
7. Plug a microphone into a tablet and begin recording. Ask questions regarding prior knowledge and experience with rip currents and the efficacy of the rip current simulation at demonstrating the proper actions to take, as well rating of its realism and immersive nature.
8. Once the interview is complete, stop recording, thank the participant, and provide compensation as desired. Save the interview file with name corresponding to date and player number as recorded in the Rip Current scene.