Download - FPSpaceInvaders: a VR game for the Oculus Rift

FPSpaceInvaders: a VR game for

the Oculus Rift

Tiago Augusto Engel

Department of Computer Science

Swansea University

This Project Report is submitted in partial fulfillment for the

Science Without Borders Programme

September 2014

Declaration

This work has not previously been accepted in substance for any degree and is

not being currently submitted for any degree.

September 4, 2014

Signed:

Statement 1

This dissertation is being submitted in partial fulfillment of the requirements for

the Science Without Borders Programme.

September 4, 2014

Signed:

Statement 2

This dissertation is the result of my own independent work/investigation, except

where otherwise stated. Other sources are specifically acknowledged by clear

cross referencing to author, work, and pages using the bibliography/references. I

understand that failure to do this amounts to plagiarism and will be considered

grounds for failure of this dissertation and the degree examination as a whole.

September 4, 2014

Signed:

Statement 3

I hereby give consent for my dissertation to be available for photocopying and for

inter-library loan, and for the title and summary to be made available to outside

organisations.

September 4, 2014

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Abstract

Virtual Reality (VR) is becoming every day more accessible. New

technologies such as head mounted displays (HMDs) are finally avail-

able to the public at an affordable price, increasing the power of en-

gagement and immersion into the virtual world. These devices aim

for an immersive experience, specially in games, and the applications

vary widely. Such devices use stereoscopic 3D images and rendering

them is nowadays a simple task, however the accuracy of the final

result is key. In a synthetic environment dangers of poor stereoscopic

renderings range from eyestrain and headaches, to users feeling nox-

ious in the virtual world, to rapid loss of interest. In this project

we look at the issue of rendering accurate stereoscopic images alone

and within the augmented reality device called Oculus Rift. From

the study of this new technology, we developed and evaluated a Space

Invaders-based game. The preliminary results show that the HMD

provides a more engaging and immersive experience, enhancing the

sense of spatial presence, focus and enjoyment.

Contents

Contents iii

1 Introduction 1

2 Background Information 3

2.1 Virtual Reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Stereoscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.1 Rendering Stereo Images . . . . . . . . . . . . . . . . . . . 6

2.2.2 Health Concerns . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3 The Oculus Rift 10

3.1 Technical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4 Game Development 13

4.1 Development Environment . . . . . . . . . . . . . . . . . . . . . . 13

4.2 FPSpaceInvaders . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.2.0.1 Design Level . . . . . . . . . . . . . . . . . . . . 15

4.2.0.2 The Player . . . . . . . . . . . . . . . . . . . . . 17

4.2.0.3 The Enemies . . . . . . . . . . . . . . . . . . . . 19

4.2.0.4 Oculus Rift Integration . . . . . . . . . . . . . . 19

4.2.0.5 3D Audio Implementation . . . . . . . . . . . . . 20

4.3 Empirical Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 21

5 Results and Discussion 23

iii

CONTENTS

6 Summary 25

6.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

6.2 Future Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

A Questionnaire 27

References 32

iv

Chapter 1

Introduction

Since the release of the movie Avatar in 2009, the world started to realize the po-

tential of 3D technology and its applications. One of the latest ground-breaking

inventions is the Oculus Rift [1]. It represents a new era on the gaming expe-

rience, the first head mounted display (HMD) to be affordable for the general

public, bringing virtual reality to a whole new level.

HMDs rely on 3D stereoscopic images to enforce the sense of depth. Stere-

oscopy increases the experience of immersion and spatial presence [2]. However,

such images arent natural to our eyes because the stimulus they produce dif-

fer from the ones of the real world [3]. This effect happens because the image

provided to each eye is produced on a flat surface. Most common symptoms

associated are eye strain, disorientation and nausea.

The challenge nowadays is to create realistic images in a way that minimizes

the problems it may cause to the users. Therefore, game designers have to take

in account several factors when designing games for such devices, having in mind

that an immersive experience depends on how the application is adapted to the

new environment. For instance, the relation of size between objects must be re-

alistic, otherwise the perception of depth may be inconsistent. Furthermore, the

head tracking device must be able to reflect the same sings given by the player in

the game, for instance if the player moves its head at a certain speed, the game

must do it the same way, otherwise the brain may lose the sense of movement

1

and acceleration, then the player may start feeling dizziness.

We present FPSpaceInvaders, a VR Space Invaders-based game where the

player relies on the Oculus Rift to track the head movements when aiming for the

targets during the game. The view is from a first person perspective, additionally,

the 3D sound system contributes to enhance the virtual reality sense, giving a

more realistic experience during the game.

The report is divided into 4 main chapters. Chapter 2 gives background

information about stereo images and how to render them, as well as applications

on HMDs such as the Oculus Rift, which is detailed in Chapter 3. In Chapter 4

we detail the game we developed and the development process to build it. Finally,

Chapter 5 evaluates the results obtained and discusses possible improvements.

2

Chapter 2

Background Information

This chapter is about defining the necessary concepts that will be used during

this report. Section 2.1 links stereoscopy and its role in the VR world, as well

as within the Rift environment. Section 2.2 gives a basic explanation about

stereoscopy and its drawbacks, while section 2.3 shows some cases where the Rift

was used as VR display.

2.1 Virtual Reality

The term Virtual Reality has been target of the media in the last few years due

to the to the incredible advances we are facing. The release of novel technologies

has brought VR to a level never seen before. VR is by no means an original

concept, as various similar concepts have been commercially available since the

early 1970s [4]. It refers to a synthetic environment created to enhance the user

interaction and immersion with the application, relying on three-dimensional,

stereoscopic, head-tracked displays, hand/body tracking, and binaural sound [5].

VR will be introduced into daily life and serve the people in various ways. Its

applications, going beyond just entertainment, could bring strong contributions

in fields such as: education, military training simulation and remote robot oper-

ation. The VR market is expected to grow exponentially in the next few years

as there are major enterprises interested in investing on these new technologies.

3

The latest deal worth mentioning is the one made by Facebook, who bought the

start-up named Oculus VR for 2 billion dollars. Sony is also working on a HMD

called Morpheus.

Stereoscopic displays play an important role in VR environments. They use

stereoscopic images to improve the users perception of immersion in the virtual

world, enabling a better understanding of the presented data, proportions and

positions of objects. Devices that use stereoscopic displays include head mounted

displays. The HMDs have become particularly popular since the release of Oculus

Rift in the last year. The next section gives a historical and technical background

about the process used to generate images used in these displays.

2.2 Stereoscopy

Ever since the early times, the man has realized that viewing with one eye (left

or right) is slightly different than viewing with both at the same time. However,

this phenomenon was not documented until 1838 when Charles Wheatstone first

explained the binocular vision and invented the stereoscope (Figure 2.1). He

demonstrated that our perception of depth is given by the combination our brain

does of the images seen by each one of our eyes.

Later on, by the end of the 19th and the beginning of the 20th century, stere-

oscopy began to attract interest from the cinematographic industry. William

Friese-Greene registered the first patent, where stereoscopic 3D films were broad-

cast on two separate screens. Viewers could then view the screens through a

stereoscope. In 1922 the first commercial 3D movie was released and the anaglyph

glasses were released. In the decades that followed, the high costs and the effects

of the Great Depression on film studios prevented large investments and the stu-

dios faced several ups and downs. The Polarized lenses were released in 1934, but

they only became popular in 1986 when IMAX released the movie Transitions,

this new technology introduced several advantages over the anaglyph glasses. It

was in 2009 when James Camerons Avatar was released that the public was truly

4

Figure 2.1: Wheatstones stereoscope

amazed with the experience. The movie was one of the most maybe the most

expensive movies ever made, due to the fact that the technology was entirely

new. Commercially however, it was worth the investment because the movie is

the highest grossing film so far, proving that the viewers are willing to pay since

the experience is worth the price.

Stereoscopy is a technique to create or enhance the illusion of depth in images.

Most methods use two images rendered with a slight horizontal offset mimicking

the different perspective through which our eyes see the world. (see Figure 2.2).

Our brains combine these images giving the feeling of spatial depth. Stereoscopic

vision probably evolved as a means of survival [6]. In games, it increases the

experience of immersion, spatial presence, and also what is known as simulator

sickness [2]. Results related to attention and cognitive involvement indicate more

direct and less thoughtful interactions with stereoscopic games, pointing towards

a more natural experience through stereoscopy. However, these advantages come

with a health concern. Section 2.2.2 discusses the possible side effects stereo im-

ages can cause to users.

5

Figure 2.2: Example of Active Stereo Image

2.2.1 Rendering Stereo Images

Rendering stereoscopic images using a graphics toolkit is a straightforward task.

There are two main ways to display the images on the screen: Passive and Active

stereo. In Passive stereo mode, two images are rendered using different polarizing

filters, and projected superimposed onto the same screen, viewers are required to

wear polarized glasses. This is the model used in cinemas. On the other hand,

Active stereo consists of vertically splitting the screen in half, left and right, and

displaying on each half an image as perceived by the left or right eye respectively,

see Figure 2.2. This mode will be emphasized on this section because it is the

mode HMDs use.

The simplest way is to render the scene once for each eye, though it isnt the

fastest way. There are several ways to render a stereoscopic scene, normally they

depend on the hardware and toolkit available. Nowadays, it is possible to find

specialized hardware to speed-up the rendering task. They usually have a quad-

buffer system, which provides front and back buffers for each eye. This hardware

6

is common in high-end applications [7].

In general, the idea to set up two virtual cameras mimicking the behaviour

of the left and right eye respectively. The virtual scene is rendered through each

virtual camera and stored in a buffer. With the screen split into two halves, left

and right, at each refresh of the screen the scene from a buffer is projected on the

respective half of the screen, with one half of the screen rendering what seen from

the left eye and the other half of the screen rendering what seen from the right

eye. To achieve an optimal effect in the final rendering three important aspects

must be taken into account:

1. distance between the cameras called Inter-pupillary Distance (IPD)

must be scaled in human proportions;

2. camera projection axes must be parallel to each other, with the left and

right views independent of one another; and

3. perspective projection mode should be used [8].

The Figure 2.3 shows how the camera model that should be adopted.

Figure 2.3: Cameras with respective projection cones [9]

2.2.2 Health Concerns

One of the biggest drawbacks of devices that use stereo images is the adverse

effects it may have on users. Recently, we see game developers being concerned

7

about the future of such technologies due to simulator sickness. Aaron Foster,

developer of the Routine [10] horror game, wrote recently on a Steam Commu-

nity update that the development team had to slow down the VR integration

due to motion sickness, arguing that though his team is very excited about the

immersion level it brings to the game, they are sceptic and, using his own words,

for now, we cant fully commit to a VR version of Routine.

Indeed, the way our brain processes a regular scene is different from a stereo

image of the scene. In the natural world, objects at different distances will pro-

vide certain amount of stimulus to the accommodative system. On the other

hand, in a computer screen there will be always the same stimulus because there

is only one focal distance, even when objects are placed at different distances

inside the scene. In other words, in the real world when we focus our view on

an object, the others around appear blurred. While on a screen, there is only

one focal distance and the entire scene is always on focus. Howarth [3] describes

in depth these topics and explains how movement, IPD, discrepancy and focus

influence the user experience.

One of the recurring side-effects reported by stereoscopic displays users is the

Visually Induced Motion Sickness (VIMS). When people are exposed to motion

e.g. traveling by car, plane, or in a cruise they may start having symptoms such

as pallor, sweating, nausea and, in some cases, vomiting [11, 12, 13]. As the

source of this sickness is our sight, the same can be induced by moving images in

displays. The VIMS is introduced when the movement in an image gives a sense

of vection (illusion of self-motion). Bles [11] defined motion sickness as follows all

situations which provoke motion sickness are characterized by a condition in which

the sensed vertical as determined on the basis of integrated information from the

eyes, the vestibular system and the non-vestibular proprioceptors is at variance

with the expected vertical as predicted on the basis of previous experience.

8

2.3 Applications

Due to the relative novel release of the technology, devices have been available for

only a year, research involving the Oculus Rift is currently limited. Contributions

are in the form of open source projects, under development, or short publications.

In this section we list the most significant contributions existing in literature.

Bolton [14] presented PaperDude, a VR cycling based exergame system in-

spired by the Ataris Paperboy. The implementation was made using an Oculus

Rift VR headset, a Trek FX bicycle attached to a Kickr power trainer and a

Kinect camera. The idea is that the user rides the bike and throws papers in

mailboxes. The Kinect sensor is used to capture the players arm movement,

providing a natural input interface. While the HMD increases the players im-

mersion in the environment.

Pittman [15] used the Rift combined with other input devices for robot navi-

gation. The results show a preference of head rotation motions other than head

gestures. The subjects found that though it could cause nausea, the head move-

ment was a very effective input movement.

Ikeuchi [16] joined a drone, Kinect and a HMD to simulate flying. A video

stream is captured and shown in the HMD, while Kinect tracks the movements

of the player. Players can control the drone through natural gestures, promoting

a realistic experience of flying.

Halley-Prinable [17] compared the level of immersion on Rift with traditional

monitors using fear. A game was developed and the subjects submitted to play

half time with the traditional screen and the rest wearing the Oculus Rift. The

players hearth rate was recorded during the experiment. From the 56 subjects,

results show that 2 people found the screen more immersive, 3 people found both

options equally immersive, and the remaining 51 people found the Rift to be

the most immersive. The author also concluded from the questionnaire and the

hearth rate data that fear level was increased when using the Rift.

9

Chapter 3

The Oculus Rift

The Oculus Rift is a virtual reality HMD developed by Oculus VR. The project

received support from the community in the Kickstarter [18] to release its first

version. Currently, only the Development Kit (DK) version is available, as the

consumer version is expected to become available in 2015. Rift is seen as the

mark of a new era for virtual reality, it is free of most of the restrictions applied

to previous products such as Nintendos Virtual Boy, CAVE environments [17]

and Nvis SX60. Virtual Boy was reported as a commercial failure due to a num-

ber of reasons including price and discomfort to use, CAVE environments are also

expensive and too large. Young [19] compared Rift and Nvis in perception and

action tasks, the results show that though some people felt less simulator sickness

on the Nvis, it is expensive and Rift consistently outperformed the Nvis on all

other aspects.

The Rift has two main components: the headset and the control box. A dia-

gram is shown on the Figure 3.1.

3.1 Technical Aspects

The company offers a Software Development Kit (SDK) [9] for developers to

adapt and build new games for the device. The first release of the development

10

Figure 3.1: Oculus Rift Headset and Control Box [9]

kit was in 2013 with the DK. Finally, the current version of the DK was released

in July 2014. The SDK offers a reliable source of code, samples and documenta-

tion about features and capabilities of the device. It also offers official support

for commercial and open-source game engines. There are normally two ways to

develop for the Rift: to use a Game Engine or to a stereoscopic rendering envi-

ronment anew.

Oculus VR offers official support for the Rift development on Unity and Un-

real game engines. Other non-commercial engines that support the Rift are also

available. On the other hand, for developers who want to create game engines

with native support for the Rift or even simple games without an engine, the

SDK offers an interface in C that can be easily used to setup the device. The de-

veloper also needs a graphic toolkit such as OpenGL or Directx. The interface in

C allows developers to link the code from other languages such as Python or Java.

One important point in the development of applications for the Rift is that

the stereo images cant be used on their own as there is a wide-angle optics in

front of the display. The lenses cause a distortion (pincushion form) and chro-

matic aberration on the edges. Therefore, there must be a post-processing step

called warping, where a barrel distortion is applied to the original image. The

comparison between both distortions are shown in Figure 3.2.

11

Figure 3.2: Image warping for the Rift

The warping is normally done at shader-level and from version 0.2 of the SDK

this functionality has been given to the SDK, which means that the developer

can simply pass the references for the textures and the API will perform the

distortion (SDK rendering mode). Also, there is the possibility for developers to

customize the distortion shaders (client side rendering), as well as combine other

shaders in the process.

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Chapter 4

Game Development

The game development process is complex, time consuming and demands a broad

knowledge of graphics, artificial intelligence, and game design; in the case of

HDMs, knowledge of all aspects related to immersive environments is also needed.

Indeed, the paradigms of game design and user interface components must be re-

vised in order to improve the user immersion and engagement with the game.

This chapter shows the games development process and the challenges we found

to work with these difficulties.

4.1 Development Environment

Before deciding how to proceed, we made a background study to understand the

concepts involved with stereoscopy (section 2.2) and developed some examples

using the OpenGL toolkit. From there, we had a look at some previous studies

involving applications (section 2.3) for the device. Then we entered on the device

itself, studying the SDK and evaluating examples in C/C++ and on the Unity

Engine (section 3.1). After building a solid basis, we decided to build a game

using an engine and apply the concepts studied.

The game was developed to the Oculus Rift DK version 1.1 with SDK version

0.3.2 preview 2 integrated with the Unity Engine Pro 4.5.2f1 [20] for educational

13

use. In this project we chose to use the Unity game engine since to build every-

thing from the beginning would have been time consuming and we wouldnt be

able to focus on the game itself. The Unity support is offered in form of a Unity

Prefab 1 which is attached to a Unity project. The scripting language used is C#

which is also the main programming language used for development in Unity.

The machine used is a laptop Dell with 4GB RAM, processor Intel Core i5-

4200U at 1.60 GHz 64 bits with a NVIDIA GFORCE 740M video card, running

Microsoft Windows 8. We also used a repository for the code maintenance. The

service is based on Git and called Bitbucket [21].

Finally, we had to create an application, having in mind that the time was

limited and the game should be simple enough to be finished and evaluated in

time. In the previous studies we found that applications in space gave very

interesting experiences to the users, then one idea came out: Space Invaders.

The idea was evaluated and validated, then we started the development process.

4.2 FPSpaceInvaders

The game developed is a remake of the classic arcade game Space Invaders devel-

oped by Tomohiro Nishikado and released in 1978. The original version is a 2D

space where the player controls a cannon and can move it sideways to shoot the

alien enemies. The enemies come in waves, attempting to destroy the player by

firing at it while they approach the bottom of the screen. If the enemies arrive

to the bottom of the screen, the alien invasion is successful and the game ends.

Figure 4.1 shows the game design.

Our remake is a 3D version where the player is a spaceship and the environ-

ment is a stellar skybox. The spaceship can move up and sideways, while the

cannon attached is controlled by the HMD sensor, which means that to aim an

enemy spaceship, the player can simply rotate his or her head towards the enemy

1Asset type that allows to store a GameObject object complete with components and prop-erties.

14

Figure 4.1: Snapshot from the original Space Invaders

and shoot with the mouse.

4.2.0.1 Design Level

The design started by looking for ways to create a realistic space environment.

First, we searched for a stellar skybox and found a generator called SpaceScape [22],

where we were able to create a skybox with stars and nebulas. The next step was

to create some planets and a Sun. As part of the environment, there are asteroids

that may hit the Player.

One important aspect in the development process is the object modeling. In-

deed, we were able to model the spaceships on Blender [23] but as this isnt our

expertise, the models turned out too heavy (memory consumption) and the tex-

tures of low quality. Thats why we decided to use the spaceship models provided

in the Unity Demo Space Shooter. They are free and can be obtained on the

Unity Tutorials website.

In order to start the game, the player has to select the options New Game or

Load Game from a main menu. The menu was designed to be different from the

15

conventional style. The player is created as a regular person on a plane and the

menu items are placed on a semi-circle around it. To select an option the player

must walk, using the keyboard, through the item. Then the action selected will

be performed. This interface offers a more natural interaction. Figure 4.2 shows

a segment menu where two options can be seen.

Figure 4.2: Main Menu View (one eye view)

Item selection by movement is an interesting aspect and can be explored in

depth due to its impact on the final user experience. Indeed, the traditional 2D

menus arent interactive and we wanted to give a sense that the player is actually

in the scene, since the moment when the game is launched.

The GameController is responsible for spawning the enemies and asteroids,

as well as manage the game flow. A Finite State Machine (FSM) was created to

handle three simple states: running, paused and idle. FSM is an elegant, simple

and extensible way to manage the game states and actions that must be triggered

16

when changing states. Game controller is also responsible for keeping score.

4.2.0.2 The Player

The player was attached to the spaceship, as if it was manning a cannon on a war

tank. To accomplish its goal, it has to shoot and destroy the enemy spaceships

before they perform the invasion. The cannon aim is attached to the HMD sensor,

which means that when the player wants to shoot a target, all it has to do is to

turn its head towards the target and press mouse left click. Also, the player is

allowed to move vertically (keys W and S) and horizontally (keys A and D) on

the screen. Figure 4.3 is a snapshot that shows the players aim.

Figure 4.3: Players aim (one eye view)

The players most important class is the PlayerController. It is responsible

for controlling audio, cannon, life, collision and movement. The Cameras are

attached to the spaceship, they are wrapped on a Unity Prefab that is given with

the SDK integration. In order for it to work in our game a few modifications were

necessary, though it was a straightforward task. The PlayerController uses the

17

cameras position and rotation to spawn bullets when the mouse is clicked, there-

fore the shot and the cross-hair will always be synchronized with the HMDs

sensor.

Another important component related to the player is the HUD (heads-up dis-

play), which consists of several pieces of information about the character. This is

important for the user experience and differs from the traditional style because

it isnt simply about positioning components on screen coordinates. We found

that components on the 3D space were better to access and created a higher level

of immersion. Here we found a lack of guidelines to such environment on the

literature, and due to time constraints, we werent able look closer into this issue.

However, there is no mandatory formula to good results, as there are multiple

ways to achieve it.

Our game contains a very simple HUD with two components: the life bar

and the level progression bar. The first was designed in a curved shape and lo-

cated on the left-hand side of the screen to follow eyes curvature, while the last

was positioned on the top of the screen. Both were designed using GIMP editor

[24]. Note that, different from the traditional paradigm, these components are

positioned in world coordinates. Game designers must analyze beforehand the

impacts the components may cause on the games course. Specially when pop-up

menus or more detailed HUDs are required, as this may cause confusion and bad

user experience if not well designed.

The player is destroyed when: (1) the enemies perform the invasion; or (2)

players life ends due to collisions with asteroids or shots by enemies. The player

has a percentage of damage it can take before being destroyed, so the incidents

mentioned in (2) may happen several times before the player is destroyed.

18

4.2.0.3 The Enemies

The enemies are spaceships whose goal is to destroy the player. In the original

game, the enemies dont have artificial intelligence, they simply are spawned on

top of the screen and fly in a zig-zag path towards the bottom. Our remake is

very similar, except that they are randomly spawned in a plane in front of the

player and fly towards a plane behind the player. If any enemy arrive to the latter

plane, the invasion is completed and the player is destroyed.

Different from the player, the enemies dont have any tolerance to damages.

Therefore, when hit by an asteroid or the player, the enemy ship is destroyed im-

mediately. For future works, it would be interesting to have some special ships,

who demand more than one hit to be destroyed, as well as special weapons.

4.2.0.4 Oculus Rift Integration

The integration for the Rift environment is one of the most important steps in

our process. Some issues were mentioned already, such as menu and user interface

components design (sections 4.2.0.1 and 4.2.0.2). Others arise such as creating

the crosshair so the player could aim the targets easily. The problem in this case is

that the crosshair cant be placed in screen coordinates, which is the conventional

way. We also added a feature to detect when a target is on the aim, changing the

crosshairs color. The last feature can easily be implemented in Unity by casting

a ray of length D from the cameras forward vector, then detecting whether it

collides with any object. This technique is known as raycast.

The Oculus VR provides two Prefabs ready to be attached on an object or

scene. The OVRPlayerController consists of a regular player controller with

a stereo camera attached. This means that it has already the attributes from

a regular player such as walking and gravity, as well as the camera controllers

already set-up for the Rift. This Prefab was used on the main menu. The second

Prefab is the OVRCameraController which consists of two configured cameras

ready to be attached to an object. This Prefab was used on the player spaceship,

19

as we have an object with different capabilities (e.g. there is no gravity in space)

and the movements are different from a first person controller.

4.2.0.5 3D Audio Implementation

An important feature added to our game is the 3D audio or stereo audio. A

3D sound simulation can improve the capabilities of VR systems dramatically.

Unfortunately, realistic 3D sound simulations are expensive and demand a signif-

icant amount of computational power to calculate reverberation, occlusion, and

obstruction effects [25]. As evidence of the computational cost, there are only a

few commercial games that use this technology.

However, as our application is not computationally heavy, we considered this

feature. First, we made an example application, in order to evaluate if it was

something worth to be added to our game. The example showed remarkable

good results, the level or localization is high anywhere the audio source is lo-

cated. Having this good experience, we decided to add the feature to our game.

Implementing 3D sound in Unity is a straightforward task, which consists of

adding the sound to the object as a Audio Source, set it as 3D sound and adjust

the parameters. Then, an audio source was attached to the three main compo-

nent of the scene (player, enemies and asteroids). It is important to notice that

this technology requires a stereo headphone, otherwise the effect will not be felt.

Figure 4.4 shows a snapshot from the unity environment, with the player and the

3D audio source.

The experiments show a really new experience when dealing with objects in-

dividually, however when several of them come at the same time, the level of

perception is lowered. To this date, the enemies and asteroids come from only

one direction and it is an open space, so the 3D sound doesnt play a decisive role

in the game. But for other styles such as first person shooters, this functionality

should have a really good effect. The combination of the Oculus Rift with the

stereo audio has the power to bring an extraordinary experience to the user, and

20

Figure 4.4: Unity 3D sound parameters and player

studies on this field must be encouraged.

4.3 Empirical Evaluation

As part of the game evaluation, we invited 10 participants to try the game and

complete a short questionnaire. Appendix A shows the questionnaire used. In

developing our questionnaire we followed the approach used by Jennet [26]. We

aimed at collecting information about users background and gaming experience,

their evaluation of our game in terms of level of engagement, immersive experi-

ence and interaction with menus and controls.

The evaluation form therefore was divided into three main sections: (1) de-

mographics, (2) game experience and immersion and (3) interactions. The first

section, demographics, regards information about participants, such as age, sex

and previous game experiences. The second section is focused more on the game

21

itself, we gather information about the participants experience during the game,

factors such as immersion, focus and sense of spatial presence are evaluated. Fi-

nally, we evaluated the players interaction with the game regarding access to

controls, performance and menus, as well as suggestions and comments.

Participants were welcomed in the laboratory and verbally informed about

the procedure, then played the game for 10-15 minutes. Finally, each participant

filled the questionnaire and was thanked by the test administrator. Please notice

that participants wore stereo headphones during the whole test in order to take

advantage of the 3D sound, as well as to prevent distractions and noises.

Most participants invited are friends with the test administrator, others are

students of the laboratory where we developed the game. All of the participants

were students, male, nine of them were 18-24 years old and one of them 25-

34. Six of them have Intermediate and one of them Expert gaming experience.

Evidencing that 70% of the participants have relevant experience in games. The

other three are Beginners. The platform most used is Desktop (9 participants),

followed by Smartphone (7 participants) and Playstation (4 participants).

22

Chapter 5

Results and Discussion

Results obtained give us a feedback about what we have done and serve as guid-

ing factor to future works. However, in-depth studies with more participants are

needed to enforce and detail the results.

Preliminarily results show that for most players the sense of spatial presence

was enhanced, and they lost track of time while playing because the game was

able to hold their full attention. These results match with [2]. Subjects reported

they felt as the game as an experience rather than simply a task, showing that

they enjoyed the activity. Subjects also reported a feeling of actually being in the

virtual world, stating that this experience was more engaging than their previous

ones.

The interactions with the game were an interesting point of this project. Tra-

ditionally, aiming for targets is done with the mouse cursor. However, as shown

in Section 4.2.0.2, our game uses the tracking device from the HMD to control the

aim. This new paradigm caused confusion on the beginning because players were

trying to move the aim with the mouse instead of the head. This phenomenon

is understandable when having the first experiences within the new environment

because participants were used to aim with the mouse, and none of them had had

any experience with HMDs.

The main menu was target of both complains and compliments. While some

23

participants pointed that the walk-through selection provided an interesting inter-

action, other thought that it could be done by approaching the item and pressing

a key to select or using mouse click. Therefore, more studies are needed to find

out which one provides the best experience.

Though most players found the game easy to control, some of them had diffi-

culties finding the right keys to press, specially at the beginning. This happened

because they cant see the keys they are pressing. A study using joysticks would

be interesting to evaluate whether it could be used as an effective replacement

for the keyboard. The stereo audio experience could be clearly noted when en-

emies were nearby, however the effect was diminished when several objects were

emitting sounds at the same time.

The general complain among the participants was the screen resolution, re-

ferring to the evident individual pixels that can be seen. Indeed, this problem

was reported by other authors [14, 15, 17] and contributed for VIMS symptoms.

Oculus VR claims that the DK2 fixes this problem by having a resolution of 960

x 1080 per eye (against the 1200 x 800 of DK1).

The minority of the participants suffered from early symptoms of VIMS after

the tests. We associated these effects to the fact that the game was designed with

continuous waves of enemies, therefore there was no intervals. It was noticed that

an unnecessary effort was demanded, and may have contributed to the symptoms

when they stopped playing. Future works should allow moments of rest, such as a

small interval between waves, when the player can relax during the game instead

of being constantly focused. Also, studies are needed to create interactions in a

way to prevent the players from moving the head too fast and abruptly. This

may cause the symptoms mentioned before, as well as neck discomfort.

24

Chapter 6

Summary

6.1 Conclusion

Recent advances on the virtual reality have brought it to a new era. One of the

most expected device was the Oculus Rift, that is the first affordable HMD to

the general population, bringing the power of the virtual world to a market not

previously explored. The applications of such devices can be found on the most

different fields of study.

In this project we developed an application to the Rift environment. Starting

by studying the stereoscopic images used on such devices, we evaluated methods

of rendering them and the dangers of poor quality. Later, we studied the Rift itself

and previous applications developed for it in order to understand what changes

in relation to the common design principles. Finally, we developed a game based

on the classic Space Invaders where the player can control the spaceships weapon

aim with the tracking sensor of the HMD, this input mode was associated with

the mouse input for shooting and the keyboard to move the spaceship. We con-

ducted a small experiment with subjects and drew some conclusions over it.

As previous mentioned, the overall experience depends on several factors al-

together. We can say that our game fulfilled its goals and good results were

achieved. The Oculus Rift indeed is a very powerful device that should become

25

widespread in the next few years, bringing immersive experiences to the con-

sumers. Efforts are being done by the game industry to adapt and build games

for this new environment. This report can be used as a starting read for beginners

on the topic, as well as to point some items that should be looked out to allow

more immersive game experiences within the Rift.

6.2 Future Works

The Rift is still on its early developments, however the perspective is very promis-

ing. The field of study created about this technology is still on its early stages,

therefore, there is a lot to be done in order to improve the user experience. Gen-

erally speaking, we found a lack of guidelines on how to create user interfaces (i.e.

menus, GUIs, HUD) that take advantage of this environment. Another challenge

is to create efficient input methods, in part prevent the users from having adverse

effects from using Rift, as well as to create interactive and immersive experiences

associating devices such as the HMDs sensor, mouse, keyboard, joysticks, cam-

eras such as the Kinect and leap motion sensors.

Specifically about the developed game, there is room for improvements and

extensions. We found the need to create a mechanism to allow the user to rest

between waves of enemies, as the lack of it may have caused an unnecessary

demand of effort from the players. Furthermore, the aspects mentioned before

about input methods apply here as well. It is possible to extend the current

game by adding special spaceships and weapons, as well as creating different

space environments. The results encourage us to carry on the work.

26

Appendix A

Questionnaire

27

Immersion Questionnaire

Please answer the following questions by circling the relevant answer.

Demographics

Sex:

Female Male

Age group:

12-17 18-24 25-34 35 and over

Occupation (please specify your field of work or study):

Do you play video-games?

Never Seldom Often

How would you rate your gaming experience?

None whatsoever Beginner Intermediate Expert

If you play video-games which of the following platforms have you used? (You can choose multiple

options)

Desktop/Laptop

Smartphone

Tablet

Playstation

Xbox

Wii

Other (please specify)

Your Experience of the Game.

Please answer the following questions by circling the relevant number.

To what extent did the game hold your attention?

Not at all 1 2 3 4 5 A lot

To what extent did you feel you were focused on the game?


How much effort did you put into playing the game?

Very little 1 2 3 4 5 A lot

Assessing Immersion

To what extent did you lose track of time?


To what extent did you feel consciously aware of being in the real world whilst playing?

Not at all 1 2 3 4 5 Very much so

To what extent were you aware of yourself in your surroundings?

Not at all 1 2 3 4 5 Very aware

To what extent did you notice events taking place around you?


Did you feel the urge at any point to stop playing and see what was happening around

you?


To what extent did you feel that you were interacting with the game environment?


To what extent did you feel as though you were separated from your real-world

environment?


To what extent did you feel that the game was something you were experiencing, rather

than something you were just doing?


To what extent was your sense of being in the game environment stronger than your

sense of being in the real world?


To what extent did you feel emotionally attached to the game?


To what extent were you interested in seeing how the games events would progress?


How much did you want to win the game?


Were you in suspense about whether or not you would win or lose the game?


To what extent did you find the immersive experience more engaging than your previous gaming

experiences?


Assessing Controls

To what extent did you find the Menu selection easy to control?


To what extent did you find the game easy to control?


To what extent did you find easy to assess your performances during the game?


To what extent did you enjoy the graphics and the imagery?


How much would you say you enjoyed playing the game?


Would you like to play the game again?

Definitely not 1 2 3 4 5 Definitely yes

Suggestions on how to improve Menus and/or interaction with Menus?

Suggestions on how to improve the Graphics?

Any other comment?

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35

Contents1 Introduction2 Background Information 2.1 Virtual Reality 2.2 Stereoscopy 2.2.1 Rendering Stereo Images2.2.2 Health Concerns

2.3 Applications

3 The Oculus Rift 3.1 Technical Aspects

4 Game Development 4.1 Development Environment4.2 FPSpaceInvaders4.2.0.1 Design Level 4.2.0.2 The Player 4.2.0.3 The Enemies4.2.0.4 Oculus Rift Integration4.2.0.5 3D Audio Implementation

4.3 Empirical Evaluation

5 Results and Discussion 6 Summary6.1 Conclusion6.2 Future Works

A Questionnaire References

Download - FPSpaceInvaders: a VR game for the Oculus Rift

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