Ray Tracer Challenge (Crystal Language)

Gregory N. Houston

To learn and practice using Crystal language, I've started the Ray Tracer Challenge (book by Pragmatic Pub).

Feedback is welcome.

Installation

TODO: Write installation instructions here

Usage

run the specs

crystal spec

Some chapters have exercises which are run separately. see below.

Work In Progress:

• Chapter 1
  • scope: Point, Vector
  • exercise simulates a projectile, writes report to STDOUT
  • crystal run src/exercises/ch1.cr
• Chapter 2
  • scope: Color, Canvas, PpmWriter
  • exercise simulates a projectile, writes ppm format file
  • crystal run src/exercises/ch2.cr -- <file_path.ppm> # defaults to ch2.ppm
• Chapter 3
  • scope: SquareMatrix
  • no exercise
• Chapter 4
  • scope: Matrix transforms: translation, scaling, rotation, skew. Fluent chaining of transformations.
  • exercise: draws a very simple clock face, 12 white dots in a circle
  • crystal run src/exercises/ch4.cr -- <file_path.ppm> #defaults to ch4.ppm
• Chapter 5
  • scope: Ray, Intersections, Sphere
  • exercise: raycasts a sphere, and several variations after transforming the sphere
  • crystal run src/exercises/ch5.cr -- <output_directory> #defaults to "."
• Chapter 6 - 16
  • TODO.

Development

TODO: Write about development experience.

I've been happy with the experience learing and using Crystal.

• very easy to learn since I already know ruby. (much easier than go, rust, and elixir which I've explored recently.)
• the compiler found some unwanted nil/null cases. which I easily eliminated.
• fibers and csp are very easy to use (see adapters/sub_pixel_stream.cr which is responsible for streaming individual elements of an RGB value. adapters/ppm_writer.cr which reads the sub_pixel_stream and handles the rules for formating a PPM file.)
• macros are a lot different than creating code at run-time in ruby. I still need to learn more here. Crystal's documentation for macros needs improving. I was expecting marcos to be a text substitution (similar to C macros). Instead Crystal macros have a mini-language and they can manipulate the AST.
• the type system works well. Sometimes I had to create similar methods for different argument types or different return types. Maybe macros could have helped DRY the code here.
• using the book Ray Tracer Challenge for a language learning exercise has worked well. its a well written book. I recommend it.

When developing, use the format tool and ameba:

crystal tool format && ameba && crystal spec

Contributing

1. Fork it (https://github.com/your-github-user/ray_tracer_challenge/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Greg Houston - creator and maintainer