A simple raytracer written in the Nix configuration language using the standard library (builtins and lib). It renders to the terminal using Unicode block characters, but I plan to adapt it to generate actual images (at some point). Currently, the renderer can handle scenes containing meshes with convex faces (though the mesh itself need not be convex) (these are triangulated at render time) and point light sources. Möller–Trumbore is used for ray-triangle intersection when rendering meshes. Phong shading is used by default. As Nix lacks trig function builtins/intrinsics, sine and cosine are approximated using Taylor series; similarly, Newton's method is used to approximate sqrt.
An example scene description (lighting, camera, objects, rendering settings) is given in scene.nix, with the renderer itself in renderer.nix and utils.nix (miscellaneous helper functions and geometry tools). Most of the settings should be self-evident, but those that may not be are (hopefully) commented. No particular units are imposed on geometry/focal length/other distances.
You will of course need the Nix package manager installed in some capacity to use this project (though running NixOS is not necessary). In ANSI mode (scene.camera.useANSI == true), something like the following can be used to render a single frame to the terminal (if the setting is disabled, the printf invocation can be omitted since there are no escape codes to interpret):
printf "%b\n" $(nix --extra-experimental-features nix-command eval --impure --expr "(import ./renderer.nix) { scene' = ./scene.nix; }" --raw)As far as I'm aware, Nix does not have a way to pause execution for a specified length of time (though printing is possible using, e.g. builtins.trace), and the renderer is currently far too slow to run in real time at a reasonable resolution -- so the best option for creating animations is probably pre-rendering via the below shell commands (or something similar):
nix --extra-experimental-features nix-command eval --impure --expr "let R = import ./renderer.nix; lib = import <nixpkgs/lib>; in lib.concatStringsSep ''\n'' (builtins.genList (t: R { scene' = ./scene.nix; sceneParams = { inherit t; }; }) 60)" --raw --show-trace > test-animation
for i in {1..2}; do a=$(cat ./test-animation); n=50; for j in {1..60}; do printf "%b\n" $(head -n$n <<< "$a"); sleep 0.1; a=$(tail -n +$n <<< "$a"); done; doneThis generates 60 frames by passing the timestep/index of each to the function in scene.nix, concatenating the results and writing the frames to test-animation. The second line reads back each frame, with delays interspersed. Note that n should be updated with the y-resolution, as set in scene.nix or equivalent.
(See the objects field in scene.nix for the definitions of these objects and the lighting and camera configuration)
TODO