Note

This is a community-maintained fork of a MIT-licensed student project in the Effective Programming with Effects course in winter semester 2025/2026. Be warned that this is not an officially endorsed project, the code in this repository may be not idiomatic Effekt.

The original repository is https://github.com/mattisboeckle/tracing-effective-rays

Table of contents

• Overview
  • Example renders
• Installation
• Useful commands
  • Effekt commands
  • Nix-related commands
• Example projects
• Repository structure
• CI

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Overview

This project is part of the "Effective programming with Effect" course at the University of Tuebingen. The aim of this project was to implement a simple raytracer based on Ray Tracing in One Weekend in the Effekt programming language.

"src/main.effekt" contains the scene, camera & rendering parameters that can be customized. The program will render an image based on the parameters and produce an image at "out.ppm".

"src/demo.effekt" contains some examples on how this project works. It is recommended to start a repl using effekt --backend llvm, import the demo file with import src/demo and then run one of the demo functions demo1() etc. which will produce an image corresponding to their name in the project root.

Example renders

10 samples, 2 bounces

50 samples, 5 bounces

100 samples, 10 bounces

Installation

Only requires the Effekt language https://effekt-lang.org/docs to be installed with at least one working backend. LLVM is recommended.

Useful commands

Effekt commands

Run the main file:

effekt src/main.effekt

This (like many other Effekt commands) uses the JavaScript backend by default. To use a different backend, add the --backend <backend> flag. The LLVM backend --backend llvm is recommended for speed, but all backends that support writing files should be supported. Only LLVM and JavaScript have been tested.

Run the tests:

effekt src/test.effekt

Open the REPL:

effekt

Build the project:

effekt --build src/main.effekt

This builds the project into the out/ directory, creating a runnable file out/main.

To see all available options and backends, run:

effekt --help

Nix-related commands

While Nix installation is optional, it provides several benefits:

Update dependencies (also runs automatically in CI):

nix flake update

Open a shell with all necessary dependencies:

nix develop

Run the main entry point:

nix run

Build the project (output in result/bin/):

nix build

Example projects using this template

• see the effekt-community GitHub organization
• This very project!

Repository structure

• .github/workflows/*.yml: Contains the CI definitions
• src/: Contains the source code
  • main.effekt: Main entry point
  • test.effekt: Entry point for tests
  • demo.effekt: Contains demo renders
  • lib/: Library code imported by main and test
• flake.nix: Package configuration in a Nix flake
• flake.lock: Auto-generated lockfile for dependencies
• LICENSE: Project license
• README: This README file

CI

Two GitHub Actions are set up:

1. flake-check:

   • Checks the flake.nix file, builds and tests the project
   • Runs on demand, on main, and on PRs
   • To run custom commands, add a step using:
     • nix run -- <ARGS> to run the main entry point with the given arguments
     • nix develop -c '<bash command to run>' to run commands in the correct environment

2. update-flake-lock:

   • Updates package versions in flake.nix
   • Runs on demand and weekly (Tuesdays at 00:00 UTC)