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

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.

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