Roller Coaster Design Tool
Liliana Kastilio May 5, 2010
Supervisor: Richard Banach School of Computer Science: BSc. in Computer Science

Abstract

This project is a Roller Coaster Design Tool (RCDT) and the aim of this project is to create a piece of software which will help the user to design and simulate a roller coaster. The report will describe some of the major design decisions as well as any problems arising during the implementation of a solution. The rst few chapters are there to familiarise the reader with roller coasters, their history and how they work.

Acknowledgements

I would like to thank my project supervisor Dr. Richard Banach for his help, advice and patience. My colleagues for moral support and my boyfriend help with understanding OpenGL and other technical advice.

Contents

1 Introduction
1.1 1.2 1.3 Project Proposal Motivation 1.3.1 1.3.2 1.3.3 1.3.4. Existing Software. Games. Professional. Previous Projects. Project proposal.
2 Background and Literature Survey
2.1 2.2 2.3 2.4 2.5 2.6 Introduction. Background. 2.2.1 Early Roller Coasters. Types of Roller Coaster Safety 2.6.1.
Roller Coaster Physics. Available Graphics API. Current Software.

3 Design

3.1 3.2 3.3 Overview GUI 3.3.1 3.3.2 3.3.3 3.3.4 3.4 3.4.1 3.4.2 3.5. View Mode Edit Mode. Modes.
Simulation Mode. Physics Mode. Components

Modelling a Track

Editing Components.

Simulation.

4 Implementation
4.1 4.2 4.3 4.4 4.5 4.6 4.7 OpenGL and Java Tools Used Structure.
GUI Implementation. Track Implementation Bezier Curves Implementation. Simulation Implementation
5 Results 6 Testing and Evaluation

7 Conclusions

List of Figures
Roller Coaster Tycoon. Sim Theme Park. Trillville:O the Rails Ultra Roller Coaster Roller Coaster Rush NoLimits 41 42
Roller Coaster Mania. Roller Coaster Creator. Roller Coaster Designer
CAD. Roller Coaster Design Tool (Benjamin London). Roller Coaster Design Tool (Johnathan Dawber) Roller Coaster Components.
Early Roller Coasters. Types of Roller Coasters. Law of Conservation of Energy Screen Mockup. Centripetal Force. Modes. Skybox image. Edit Mode Example Bezier Curve Bezier Calculation.
OpenGL pipeline. Bezier Curve Calculation Cart Edit.
View. Naming the Coaster Edit Component Edit Component Edit Component View Mode

Creating the Coaster.

Third Person View. First Person View

Introduction

Project Proposal
Roller coasters around the world have thousands of visitors everyday, they are the end product of years of designing and precise engineering. Statistics imply that you are more likely to die from accidental poisoning (1 in 193 chance) than due to a roller coaster malfunctioning (chances are 1 in 300 million)[6], yet the safety aspect of the ride is taken extremely seriously. The complex nature of roller coasters make them hard to design and test, which is why computers are used to accurately simulate them before they are built. It is important for the simulation to be as accurate as possible because an amusement park cannot simply pack up and move to another place if somebody gets injured, so you can see why the roller coaster manufacturer's reputation is extremely valuable and worth protecting at all costs. There are millions of pounds invested in coasters so the testing should be done before the they are built to save money and lives.The aim of this project is to create a roller coaster design tool, which will allow the user to create a roller coaster track segment by segment, so that each one is editable in a 3D enviroment but is user friendly and intuitive. After the track is complete an accurate simulation should be run on the coaster to analyse it based on physical laws (e.g. gravity, friction). If the coaster is deemed unsafe at certain points, they should be highlighted in some manner and the user should be informed. The interface should be highly usable and ecient once the user has learned it. The project concerns creating a Roller Coaster Design Tool which combines features of Roller Coaster Tycoon and No Limits. Currently roller coaster related software is only available in the form of games or professional software. As such, a space exists in the market for something in between; an application that is fun to use whilst adhering to important laws of physics with an emphasis on safety. The aim is to create a simple, user friendly software that will allow the user to create a roller coaster from scratch and be able to edit it in an intuitive manner.

View statistics (ride length in minutes and the amount of Gs the ride is subjected to during various points on the ride)
Background and Literature Survey
The following is a short description of the history of roller coasters, how they work, their structure and some fundamental physics. Some of the popular roller coaster games and professional software is shown in 2.6. The dierent features of the available applications justify several of the functional requirements for this project detailed in 1.3.4.

Background

Roller coasters are a thrilling ride, where the passengers are usually secured into their seats during the ride which has twists, turns, hills and sometimes loops and various other elements. In order to understand what a roller coaster is the individual components must be discussed and comprehended. In general a coaster consists of a chain of connected cars which move on tracks, it has no engine or power as such of its own and is moved by gravity and momentum. Figure 13 shows some of the main roller coaster components, which are :
The track is similar to train rails and denes the overall shape of the

coaster.

Train cart
The train cart is part of the train and carries passengers. It may
be attached to the track in several dierent ways depending on the type of the roller coaster, the dierent types are described later (section 2.3 ). The cart can be attached to the track from above, be inside the track or rest on top of the track.
Course/Circuit Chain lift
The circuit denes the complete track from start to nish.
The chain lift pulls the train up the rst hill so that the train can
gain enough momentum as it accelerates down the hill to complete the course.
Figure 13: Roller Coaster Components

Early Roller Coasters

Early 19th century roller coasters were called Russian Mountains ( The Incredible Scream Machine: A History of the Roller Coaster , Robert Cartmell (1987), page 19) which refer to slides made of ice, this along with French toboggan slides and switchback railways are considered the predecessors of modern day roller coasters (The Golden Age of Roller Coasters, David W. Diane (2003), page 7). These thrilling slides have sparked the idea of a theme park with rides where customers can pay to enjoy the experience and the rst coaster to be patented was the Gravity Switchback Railway (g 14a) by LaMarcus Adna Thompson in 1885, who is known as the father of the Gravity Ride. By 1817 at least two more rides were constructed in France; Les Montagues Russes a Belleville (The Russian Mountains of Belleville) and Promenades Aeriennes (The Aerial Walk). These rides featured cars that locked to the track A History of the Roller in some manner ( The Incredible Scream Machine:

is the rate of change in velocity, which is measured in
Gravity is a force of accelration.
is the speed of an object travelling in a specic direction and is

measured in

is the energy stored withing an object as a result of its When an object starts moving away

Potential energy

height relative to the starting position.
from the ground (upwards) kinetic energy decreases as potential energy increases (gure 16). Potential energy can be calculated as follows:

P E = mgh

where:

PE m g h

is the kinetic energy (Joule)
is the mass (kg) is the gravity (

m s2 )

is the height (m)

Kinetic energy

is the amount of energy an object has depending on its mass
and velocity. Any object which has motion has kinetic energy. It can be calculated using the following formula:

1 m v2 2

v is the velocity ( m ) s m is the mass of the object (kg)
The law of Conservation of Energy states that energy can be changed from one form to another, but it can not be created or destroyed (gure 16).
Figure 16: Law of Conservation of Energy

Friction

this force acts in the opposite direction of an object that is moving
along a surface (http://www.funderstanding.com/help) and can be calculated with the formula:
is the coecient of friction is the mass of the object

Centripetal force.

Along with the seatbelt (which is sometimes almost ir-
relevant) this force helps keep the riders in their seats. When going around the loop the centripetal force pulls you towards the center of the circle created by the loop which changes the direction of the train car. At the very top of the loop gravity is acting on the rider in the downwards direction but the rider still experiences a force that pushes into the track (upwards) as opposed to downwards. This force is the reason the cart continues to move around the curved path. A loop is part of a circle and the centripetal force continuously pulling towards the centre of the circle keeps changing the direction of the car(Figure17a). The rider feels pushed into their seat due to inertia (the cart constantly changing direction and the rider not moving at the same velocity). The roller coaster is designed such that the imaginary path goes higher than the constructed loop ( Figure 17b). This imaginary path is the threshold for the centripetal force to be enough to carry the cart around the loop and as such the loop must be constructed below this threshold.

Figure 17: Centripetal Force

Safety

The reason this type of project is important is that if implemented well it can help prevent accidents by letting the user know if there are any safety issues in
the track design. By displaying warnings when any of the structural components are dangerous or if the design is unfeasable the system can quickly and eciently alert the user to important issues and guide their correction. accurate nothing could go wrong. Most people experience the feeling of weightlessness when the car goes over a bump or when the roller coaster goes over the top of a hill, this is all part of a thrilling experience. It occurs when there is no force to support your body and This can also prevent any problems when building the coaster as if the simulated design was
m s2 ). The reason you dont feel it all the time is because when you are standing on the oor or
you are eectively freefalling (accelerating downwards at 9.8 sitting down, the oor or the chair is pushing up at you whilst you are pushing down on it. This is what we perceive to be the feeling of weight. G-forces along the spine are the most dangerous ones, they push the blood away from the organs; especially the brain and the eyes. Graying out, loss of vision and blacking out are the dangerous eects of experiencing high g-forces and g-induced loss of consciousness and possibly death are the worst that could happen to you on a ride. (Best Life magazine, October 2007, page 125) G-force feels exactly the same as the force of gravity, in fact 1g is equal to the acceleration you feel due to gravity near the Earth's surface ( 9.8
m s2 ). At 0 g's the rider would experience the feeling of weightlessness, 1g is the normal
tug of gravity on the body, at 6 g's the rider would have a nose bleed, above 8 g's the rider would pass out and as the g's increase a higher risk of death is introduced. There are a few fundamental rules to ensure the ride is as safe as possible:
the rst drop must be higher than any other part of the roller coaster, this ensures that the train has enough energy to make it all the way to the end of the circuit.
the passengers must not be subjected to more than 3.5 g's there must be 3 sets of wheels on every roller coaster:
running wheels, which are responsible for the speed of the coaster and lie on top of the track (or below if the coaster is of an inverted type) friction wheels, which are located on the side of the track and help with side to side motion so that the cart doesn't y o the track. up-stop wheels, which keep the cars from falling when upside down in a loop ( due to the physics behind the loop this would not happen anyway unless the coaster did not have enough energy to make it all the way through the loop, but the wheels are included as an additional safety component)

Current Software

Available Graphics API
is the most widely used graphics libraries for interactice 2D and 3D applications. The advatages of using OpenGL are that it is an industry standars, it is easy to use and the documentation is very informative and complete. OpenGL can be used on any platform which makes it perfect for commercial and mobile applications.

OpenGL

DirectX
is produced by Microsoft and proved a set of API's video and sound Is compatable with.NET and has a graphics API Direct3D for

cards.

visualisation and interaction in a 3D enviroment.

Design

Overview
The idea behind this project is that the software is powerful and ecient yet user friendly and easy to use, as much of the work as possible should be taken away from the user and the software should make correct assumptions and predictions or at least suggest them. For example, instead of the user worrying about the safety of his model RCDT (Roller Coaster Design Tool) will simply output a warning when there is a safety issue with a meaningful message. This way the user doesn't have to know much about the structure of roller coasters or how they work but still end up with a model which is safe and rational. In this chapter some major design decisions are discussed as well as any ideas on how to implement them.
After researching the currently available tools for designing and simulating a roller coaster (mentioned in sections 1.3 and 2.6) it was clear that the GUI for this project would have to be more like the simple interfaces seen in the games rather than the professional tools in order to make it simple and user friendly, capable of accommodating novice users. As seen in Figure 3.2 (a wireframe mockup of the GUI) the number of buttons is kept to a minimum, they are not too small (unlike CAD and NoLimits) and later on after the implementation stage the icons on the buttons reect their intended use. The design is clean and not confusing, which makes it more user friendly and not intimidating. When hovering over the button the user will be able to see the name of the tool as a tooltip, which should be as descriptive as possible. There are two working views:
main view - where the user can view/edit or watch the simulation depending on what mode they are in ( discussed in 3.3) small view - where the user can see the model from a dierent angle if he is in

View/Edit mode.

This will make previewing and editing of the model easier, without having to switch to a dierent view or move around the scene too much.

Figure 18: Screen Mockup

It was decided that the software should have the following modes:

View Edit

displays the empty three dimensional world if no track has been created
yet, otherwise displays the track that has been created in the

Edit mode.

in this mode the user can create and edit a roller coaster component by component. ware. This along with
View mode are part of the Design mode,
which is an abstract concept that does not directly exist within the soft-

Simulate Physics

in this mode the user can see the cart move along the created track,

this also has

First Person View so that the user can view the simulation
as if on the front row of the ride. this mode can be toggled on and o, it simulates the ride with con-
siderations of speed, friction, gravity taken into account.

Figure 19: Modes

View Mode
When in this mode for the rst time the user simply sees an empty scene, before any more can be displayed the user would have to either load a coaster, open a le or go into edit mode and create a coaster or part of it. The user can look around the three dimensional scene with basic, user-friendly controls and view their design from the top, side or straight on. In this mode the cart is not diplayed as only the coaster track is important at this stage. This would improve the rendering times of the program as less polygons need to be rendered per frame. For simplicity the initial implementation does not have scenery, which later can be simulated by adding textures to the oor as grass and a sky box around the whole scene. A sky box is simply a cube with textures on each side, such that when the user looks around it seems that he is in a simulated world with a sky and sun or possibly a landscape depending on an image. An example of an image that can be used as texture for a skybox is shown in Figure 20

Figure 20: Skybox image

Edit Mode
Within this mode the user is able to view their design in 2d perspective and edit t. It has been decided that the view in this mode is directly from the top which would mean that the user can only edit in this mode in 2 dimensions and the height of the the track would be edit in the View mode or by using a tool. The side window at this point would display the 3d version of the track as it is designed with a coded in height. Figure shows what the user screen may look like, where the curved track consists of segments all of which have control points (discussed in more detail in 3.4.1) and in the smaller window the 3d model of what is designed in this 2d mode is shown.
Figure 21: Edit Mode Example

Simulation Mode

Simulation mode, these are:
where the user can watch the cart go around the track as
There are dierent views in the
First person view Third person view
if at the front of the train of the roller coaster. where the user simply watches the cart go around the
track from a distance and can move around the scene to get a dierent
The implementation of this is discussed in more detail later on.

Physics Mode

In this mode the dierent forces discussed earlier in section 2.4 are modelled during the simulation. If all the forces are turned on, then the train cart whould speed up when going down the hills and loops and slow down due to friction or the cart running out of potential energy, which means that it would stop naturally and not due to braking system. Braking system could be implemented at a later stage, its purpose is to force the train cart to a stop or slow it down to keep the speed and g's within a safe limit.

Components

In this project it has
In order to understand how the components of the track are modelled, a data structure for those components needs to be described. 22 shows the structure of a bezier curve. end points of the curve and points Points been decided to use Bezier curves to model the curves within the track. Figure

are the start and The

are the control points of the curve,
which means that the position of these denes the shape of the curve.
coordinates of all teh points are used to calculate the distances between

p1 (line

A) and between

(line B).

Figure 22: Bezier Curve
In order to calculate the curve each point's position is calculated separately, Figure 23 shows how that calculation is done. When the length of line A is known the number of steps need to be coded into the software, this determines how smooth the curve is going to appear. For a shorth curve as few as 20 look very smooth, for a longer curve anything up to 200 steps is needed. By taking very small steps we can make a triangle and using geometry calculate the length of all the sides. After that calculation is done we know where to draw the next curve point, this is done repeatedly until we reach the end point (p4 ). The end result is a smooth curve between the start and end points
Figure 23: Bezier Calculation
One of these curves makes a track component. In order to have a full track many of these components need to be added one to another and edited separately. To simulate the tracks continuity every proceeding component's start point is the same as the preceeding component's end point. When the shared point between components is edited the curve is recalculated for both components. Doing this enables the track to look like a continuous curve due to The coordinates of each point are stored as a the nature of the calculation.

Implementation

OpenGL and Java
RCDT is in Java it uses JOGL (which is an OpenGL implementation).
The IDE chosen for this project is Netbeans since it makes creating GUIs and testing the application easier. Figure 4.1 represents the structure of OpenGL pipeline (Khronos Group, http://www.khronos.org/opengles/2_X/img/opengles_1x_pipeline.gif ):
Figure 24: OpenGL pipeline

Tools Used

Tools that have been used to create this project an the report:
NetBeans ( Java + JOGL) L X Y Sequence Diagram Editor For UI OpenOce AC3D Adobe Photoshop SmartDraw

Structure

The 3D world is modelled in a 3D coordinate system, where the

x and y axis

correspond to the pixels on the screen. This is so that when interaction occurs translating between screen coordinates and world coordinates is easier. The structure of an interface between the
RCDT is such, that the RollerCoasterModel class acts as MainWindowManager (GUI) and the ThreeDWindow-
Manager (OpenGL) classes. This is done so that no unncessary operations are
done in the class which does not have the information required. In general the GUI and the main application need to be kept separate as to improve the scalability of the software, the changes in the GUI do not require direct changes in the whole of the program. The
RollerCoasterModel class passes information be-
tween the classes when required and does any preparatory work and checks. For example, when the user wants to add a new component and presses the
AddComponent button the RollerCoasterModel class does all the required computation that is needed before calling the relevant method in the TrackComponent class.
There is only one track array at any one time, and to make sure that the array is properly maintained all the adding and deleting from the array can only be done by accessing the relevant methods in the
RollerCoasterModel class, this
way there is no duplication of track array data or any inconsistencies.

GUI Implementation

There is a grid with in the
Edit mode which is implemented in the main display
loop of OpenGL, this is only drawn when the user is this mode. Otherwise the 3d scene is drawn, which consists of a plane which acts as the ground for the roller coaster. The view can never see below negative
z coordinates as restrictions are
placed. When in 3D view the grid is not drawn any more and instead the 3D scene along with the track components are drawn. Since it is almost impossible to sucessfully design a roller coaster by manipulating all 3 coordinates (x, at the same time, only coordinates Edit view and the
y, z ) x and y of the component can be edited in
z coordinate is coded in.

Track Implementation

The track has been implemented as an array of components, each of those components is an object which consists of four points. There are two types of points: end point and control point. and A point is an object which has an x, y z coordinate. Each component has two End points and two Control points.
When a new component is created the system simply generates the position of those points in relation to the last point of the track or if the component is the rst component in the track array then the position of those is always the same. So every time a new track is created the rst component is always in the same position but it can be edited or moved after it is created.
Figure 25: Bezier Curve Calculation
Bezier Curves Implementation
Each OpenGL loop while the program is running the track is drawn by going through each component in the component array and retrieving the associated points, after that is done the points are used to calculate each little bit of the curve to be draw, using the code shown below. This is done for every single segment of the curve as well as every component. This is alot of computation to be running constantly at slows down the whole program.
Simulation Implementation
For every loop RCDT checks what mode the user is currently in, if the mode is changed to
Simulation mode, the teapot ( which is used to represent the cart
as the code for importing 3D objects has not been implemented, the picture of the cart can be seen in Figure 26) is moved one point from the track array at a time. Unfortunately the cart will seem to be accelerating or slowing down depending on whether the points are dierent distance apart. This could be solved by computing new points, using the already stored coordinates, an equal distance apart and storing them in a new array which is to be used for simulating the cart movement

Figure 26: Cart

Results
Figure 27 shows the default state of the program after the user has loaded the application. This state depicts the view mode with no coaster components visible (as none exist as of yet). Four menu items exist down the left hand side of the screen representing the view mode, the play mode, the edit mode and the simulation mode. In order to begin development the user must enter the edit mode by clicking the edit button.

Figure 27: View

Figure 28 shows view is switched to a top-down alternative and a grid is shown for reference. Menu buttons are available on the right side of the screen. Their functionality is add course/component (plus), delete component (cross) and traverse between components (arrows). The user can begin by adding a course and clicking on the add course menu button.

Figure 28: Edit

Figure 29 shows a dialogue box appear prompting the user to input a coaster name. After a name is input and conrmed the user may begin creating a course.
Figure 29: Naming the Coaster
Figure 30 shows the rst component appear in a default state (a quarter circle) with dened control points. At this point the user may view the component in three dimensions, continue editing or add another component. In this use case the user continues to edit the component.
Figure 30: Creating the Coaster
In Figure 31 he user left clicks in the left sector of the edit grid to place the start point. Note that the control points and end points do not move. In order to move on to the next point the user now double clicks on the placed point.
Figure 31: Edit Component
In Figure 32 the user now has the same control as the previous use case step but now the rst control point is manipulated as opposed to the start point. This control point aects the shape of the bezier curve between the start and end points but does not move either one. In order to move to the next control point the user, again, double clicks a chosen location.
Figure 32: Edit Component
The user now continues to manipulate the second control point (the bezier curve from the side of the end point). This works in much the same way but instead modifying the half of the curve closer to the end point. The user may now double click a location for the end point if desired. Instead of placing the end point the user keeps the default and clicks the view button to return to the view mode (Figure 33).
Figure 33: Edit Component
The user is now in view mode and traverses the scene using the W (forward), A (left), S (backward) and D (right) using the mouse to pan and look around. The user can see the constructed coaster in three dimensions but no cart is visible until the user switches to simulation mode. The user clicks the simulation button on the menu on the left and moves to the simulation mode (Figure 34).

Figure 34: View Mode

As you can see in Figure 35 the user can now see the cart (represented here by a red teapot due to problems importing the cart object le) moving at a constant speed around the track. the scene in any way. The view follows the cart several vertices behind on the same course as the cart. In this mode the user cannot traverse

Figure 35: Third Person View
In contrast in Figure 36, the user is much closer to the cart object due to the dierence in spacing between vertices along the constructed course. In simulation mode the user is constantly several vertices behind the moving object. As such, if those vertices are separated by dierent amounts this has the eect of the user moving closer and further away from the object (depending on whether the spacing decreases or increases).
Figure 36: First Person View

Testing and Evaluation

1. Create a roller coaster track segment by segment - this feature still needs improving, adding teh next segment works unless the user edits any of the subsequent segments which calculates the bezier curves between points incorrectly due to accessing the data in what seem s to be the wrong order due to the point between segments being shared. 2. Edit each segment in all 3 dimensions - thsi has only been implemented in the 2D view and the user can drag the points to a new position, RCDT records the new coordinates and edits them in the array. 3. Imply whether each segment is to be a curve or a straight line ( the user should not have to select a dierent tool if possible) - the straight line has not yet been implemented as the creation and visualisation of the bezier curves is still buggy. In order to add this feature a tool would have to be created where the user can select the type of line that they require. Due to the way teh RCDT is implemented at the moment simply letting the program make the decision for you is not feasible. 4. Conrm that each segment is connected to the previous segment seamlessly - this seems to work well unless there are more than two segments, the error is due shared point between segments which can easily be xed once objective number 1 is xed. 5. Select a start and end point to the roller coaster track ( full circuit or not) - at the moment the user could in theory have a full circuit, although the rst point is not actually shared with the last point of teh track. 6. View a simulation of the ride from third or rst person view points - this has been implemented but can be improved in quality by adding more polygons to the track and making it look more realistic. track would be an improvement. Also a better frame rate and a more accurate simulation of the cart going along the
Here is an evaluation of the key objectives mentioned in Chapter 1:
The rest of teh features mentioned below have not yet been implemented, and have been moved to the wishlist: 1. Save, load, edit and delete roller coaster tracks 2. Experience an accurate physics simulation (some implementation of gravity, acceleration, friction) 3. Save a coaster 4. Load a coaster 5. Be informed of critical safety problems and be able to view non-critical problems

6. Make use of a help system when the method for performing a certain task is not immediately apparent 7. Traverse the scene in the presence of a realistic environment (with scenery and a skybox) 8. View statistics (ride length in minutes and the amount of gs the ride is subjected to during various points on the ride)

Conclusions

Each requirement that was fullled, however,
Overall RCDT has not been as sucessfull as expected, the tasks were found to be alot harder than originally predicted. Modelling the curves of the track have proven to be a real challenge. gave immediate rewards when implemented correctly.

References

[1] Amazon.co.uk: video games. rollercoaster video games: PC & http://www.amazon.co.uk/rollercoaster-
1/s/qid=1271976757/ref=sr_pg_1?ie=UTF8&sort=salesrank&keywords=rollercoaster&rh=i:videogames,k [2] Atari video games. http://www.atari.com/games/rollercoaster_tycoon. [3] LucasArts.com | thrillville: O the rails.
http://www.lucasarts.com/games/thrillvilleotherails/. [4] NoLimits - rollercoaster simulation. http://www.nolimitscoaster.de/. [5] Reactor software | ultra coaster. http://www.reactorsoftware.com/. [6] Reality check: Odds of dying. http://www.squidoo.com/oddsdying. [7] RollerCoaster mania (PC) : Read reviews and compare prices at ciao.co.uk. http://www.ciao.co.uk/RollerCoaster_Mania_PC__7117250. [8] Sim theme park for PC - sim theme park PC game - sim theme park computer game. http://uk.gamespot.com/pc/strategy/simthemepark/.

Appendix