rcoaster

An OpenGL-powered roller coaster simulator with configurable spline-based tracks.

Description

• Catmull-Rom splines are evaluated via recursive subdivision to determine the camera pose and track model along the spline.
  • Each spline is defined by the control points found in the input spline file.
  • The camera moves in a continuous path and orientation.
• The track model consists of a pair of rails and a sequence of crossties.
  • A rail has a T-shaped cross section.
  • All neighboring pairs of crossties are separated by the same distance.
• Textures are mapped to the models for the sky, ground, and crossties.
  • The image files corresponding to the textures are designated via command-line parameters.
• The scene was displayed at 60 frames per second on the Retina display of a 13-inch Macbook Pro from early 2015.
  • Vertical synchronization seemed to be enabled by default on the Macbook Pro.

Build Requirements

• Operating system: macOS or Linux
• C++ compiler supporting at least C++17
• CMake >= 3.2
• OpenGL >= 3.2

My development environment and tooling:

• Hardware: MacBook Pro (Retina, 13-inch, Early 2015)
• Operating system: macOS Mojave == 10.14.16
• C++ compiler: Clang == 10.0.01
• CMake == 3.25.1
• OpenGL == 4.1

I built rcoaster on a Linux machine as well:

• Operating system: Debian == 11.7
• C++ compiler: gcc == 10.2.1
• CMake == 3.26.3
• OpenGL == 4.5

Make sure to install the following packages on Linux:

• libglew-dev
• freeglut3-dev

Build Steps

The build system must be generated before the project can be built. From the project directory, generate the build system:

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE:STRING=Release ..

The -G option is omitted in cmake -DCMAKE_BUILD_TYPE:STRING=Release .., so CMake will choose a default build system generator type based on your platform. To learn more about generators, see the CMake docs.

After having generated the build system, go back to the project directory:

cd ..

Build all the targets of the project:

cmake --build build --config Release

The built targets are placed in the directory build. There is only one executable target: rcoaster.

Usage

./build/rcoaster [options...] <track-file> <ground-texture> <sky-texture> <crossbar-texture>

Options:

• --max-spline-segment-len <length>
  • The maximum length of each spline segment generated from recursive subdivision.
  • The default option argument is 0.5.
• --camera-speed <speed>
  • The camera movement rate in spline segments per second.
  • The default option argument is 100.
• --screenshot-filename-prefix <prefix>
  • The filename prefix of any screenshots generated.
  • Screenshot filenames follow the format <prefix>_<count>.jpg, where count is formatted as a 3 digit integer.
    • For example, if prefix is "screenshot" and count is 17, then the filename would be "screenshot_017.jpg"
  • The default option argument is "screenshot".
• --screenshot-directory-path <path>
  • The directory path where any screenshots taken will be saved.
  • The default option argument is ".", which is the current working directory.
• --verbose <verbose_output>
  • An option argument of 1 enables verbose output to stdout, and an option argument of 0 disables it.
  • The default option argument is 0.

Any screenshots taken are saved as JPEG files. Video is a series of screenshots. To take a single screenshot, press i. To start recording video, press v. To stop recording video, press v again.

To exit the program, have the window in focus and press ESC. You can also terminate the program by pressing CTRL + C in the terminal.

Example

./build/rcoaster track.txt textures/grass.jpg textures/sky.jpg textures/wood.jpg

Track File

A track file lists the spline files to load to create the track. The first line is the number of spline files to load. Each subsequent line is a path to a spline file. Paths may be absolute or relative. Relative paths are relative to the current working directory of the rcoaster process.

Currently only the first spline file listed is used.

An example track file is track.txt.

Spline Files

A spline file contains the control points of a spline. The first line consists of two space-separated fields: the number of control points and a number indicating the type of spline. Each subsequent line is a control point.

Currently the only supported spline type are Catmull-Rom splines. Use 0 in the spline file to indicate a Catmull-Rom spline.

Example spline files are in the directory splines. I tailored the spline file custom.sp to produce a track optimized for my hard-coded scene size, ground size, and sky box size. The other spline files were for initial testing testing and unfortunately produce tracks that are too small for my current configuration.

Texture Files

Textures are provided as either JPEG or PNG files. Example texture files are in the textures directory.

References

• Calculation of Reference Frames along a Space Curve
  • By Jules Bloomenthal
  • Bloomenthal gives credit to Ken Sloan for the technique I implemented to propagate reference frames along the spline.