raytracing-cpp

A from-scratch offline path tracer implementing the full Ray Tracing in One Weekend series in modern C++17.

Follows the three books by Peter Shirley et al:

• Book 1 — Ray Tracing in One Weekend: Lambertian / Metal / Dielectric, defocus blur
• Book 2 — The Next Week: motion blur, BVH, checker / image / Perlin textures, quads, lights, volumes, Cornell box
• Book 3 — The Rest of Your Life: Monte Carlo integration, PDFs (cosine / sphere / hittable / mixture), ONB, importance sampling
• Bonus — Möller–Trumbore triangle + minimal OBJ loader (Stanford Bunny, 69k tris, BVH-accelerated)

Multithreaded row-parallel renderer (std::thread + atomic work queue). Outputs PPM and PNG (via stb_image_write).

Build

cmake -S . -B build
cmake --build build -j

Requires C++17, CMake ≥ 3.16, and a POSIX threads implementation.

Run

./build/raytracer <scene>

Available scenes:

Scene	Output
first_light	first_light.png — Book 1 material showcase
book1_final_preview / book1_final	Random sphere scene
checkered_spheres, earth, perlin_spheres, quads, simple_light	Book 2 feature demos
cornell_box(_preview)	Brute-force path-traced Cornell box
cornell_box_mcmc(_preview)	Same scene with importance sampling
cornell_smoke(_preview)	Cornell with volumetric smoke boxes
book2_final(_preview)	Book 2 all-in-one final scene
icosahedron	Triangle-mesh material showcase
bunny(_preview)	Stanford Bunny via OBJ loader

Rendered images land in output/<scene>.{png,ppm}.

Sample outputs

Selected images (output/):

• cornell_box_mcmc.png — 600×600 @ 1000 spp, 3 min 48 s with light importance sampling
• book2_final_preview.png — motion blur + volumes + emission + textures + BVH
• bunny_preview.png — Stanford Bunny (35,947 verts / 69,451 tris)

Structure

src/
  rtweekend.h    — shared utilities, constants, RNG
  vec3.h, ray.h, interval.h, color.h
  aabb.h, bvh.h                  — BVH acceleration
  hittable.h, hittable_list.h    — scene graph + transforms
  sphere.h, quad.h, triangle.h   — primitives
  material.h, texture.h          — shading
  perlin.h                       — noise
  onb.h, pdf.h                   — Monte Carlo sampling
  camera.h                       — threaded render loop
  rt_image.h, png_writer.h       — I/O
  obj_loader.h                   — minimal OBJ mesh loader
  constant_medium.h              — participating media
  main.cc                        — scenes + entry
external/
  stb_image.h, stb_image_write.h (from nothings/stb)
scenes/
  earthmap.jpg, bunny.obj        — assets

References

• Ray Tracing in One Weekend series — Peter Shirley et al.
• stb single-header libraries
• Stanford Bunny OBJ via alecjacobson/common-3d-test-models