Show HN: I wrote a C++ ray tracer from scratch without AI

by martiano • 1 month ago

155 64 1 month ago

martiano9• 1 month ago

Hey HN,

5 years ago I was 17 and learning to code C/C++ in a coding bootcamp (42). One of the projects was a simple C ray tracer. I really enjoyed working on the project and always loved computer graphics, so I decided to create my own path tracer from scratch, in C++, without using any third-party libraries.

I ended up working on it consistently for over a year, then sporadically when CG excitement hit me again. Recently I polished it and completed some unfinished features and decided to make it public, finally. It's a C++20 Path Tracer with a CPU renderer. It is able to render good-looking images with reasonable performance and sample count.

Btw this was initially coded without AI, but I've used it for the recent clean up and features. This project is a personal favorite of mine, and it can improve a lot, so I'd love to hear your feedback.

ttoinou• 1 month ago

Congrats ! Results look stunning

shinycode• 1 month ago

Congrats on doing 42 and to have worked and shared your project, very nice results !

hresvelgr• 1 month ago

Great work, the examples look fantastic. I will say, it's misleading to put "without AI" in the title for you to then comment on your submission that you have in fact used it. While it may only be in a trivial capacity, you've still used it.

martiano9• 1 month ago

I get your point. I consider it fair with the disclaimer because the "manual" version was very similar to current but missing some love

pixelesque5• 1 month ago

JFYI: Your inverse ray direction calculation is not NaN-safe: if rays are completely axis-parallel in one dimension, so the direction value is 0.0 for that axis, you'll be doing the val / 0.0 which results in a NaN...

Also, as you're using full double/f64-precision all the time, you're leaving a fair bit of performance on the table: transcendentals (sin(), cos(), etc) in particular - can be a lot slower than when using f32, and generally double precision can be special-cased to particular areas of the renderer that need it (curve, sphere intersection, and some situations where volume scattering produces very small distances).

deliveryboyman• 1 month ago

What's the proper way to handle a zero in the direction vector when calculating the reciprocal direction? Should it evaluate to infinity?

adrian17• 1 month ago

Also, as you're using full double/f64-precision all the time, you're leaving a fair bit of performance on the table

There's another issue that popped up on my quick naive profiling run: std::shared_ptr<Material> in the HitRecord/HittableLightSample is assigned/copied and destroyed a lot, and somehow these refcount operations show up as half of all samples on my profile (presumably because even if there's no hit and the pointer stays nullptr, the smart pointer still must check if there's anything to deallocate).

martiano9• 1 month ago

Implemented this and the other improvements suggested on the thread. Performance up by 20%! Thanks for the feedback. https://github.com/themartiano/luz/pull/3

pjmlp• 1 month ago

Congratulations on achieving it.

smartmic• 1 month ago

Btw this was initially coded without AI, but I've used it for the recent clean up and features

Then it makes sense to update the submission title. To me it reads as if the project was written completely without the help of AI (which might be a quality badge to some), but it is not 100% true then.

Anyhow, cool project ;)

martiano9• 1 month ago

Thanks! I get your point about AI, but I think it's fair to say it's almost 100% AI free. I worked on it for ~15 months, vs 1 week now with AI. Previous results were quite similar

manoji• 1 month ago

Hey ! Great work , I wanted to try something like this as well to begin my journey into games and computer graphics . I would love to know what resources you used to learn.

martiano9• 1 month ago

The greatest resource I've found on the internet is the Ray Tracing in One Weekend series. (https://raytracing.github.io/) You can start there and go pretty far. Also you can mix random papers you'll find and eventually just testing and experimenting yourself.

MyHonestOpinon2• 1 month ago

Amazing. What happened with your professional career ? Did this exercise help you out professionally ?

One of my worries about AI is that doing these deep dives are a lot harder to justify.

martiano9• 1 month ago

I just launched the project, so can't say it helped me professionally yet. Almost all of the time invested in this was pre-AI. I agree it's harder to justify those deep dives but still worth it if you do it alongside AI IMO.

yardie• 1 month ago

How did you like 42? Would you recommend it? I worked some great devs who came out of 42. They all wanted to be game developers. The industry is notoriously unreliable. So they pivoted to writing business software where the client actually pays you for more features. LOL.

cultofmetatron• 1 month ago

for anybody else interested in this undertaking, I recommend this book https://pragprog.com/titles/jbtracer/the-ray-tracer-challeng...

Alifatisk2• 1 month ago

without AI

Now this is how you catch attention

glouwbug• 1 month ago

I expect similar headlines like “I saved on token cost by hiring juniors” to come in soon too

gspr2• 1 month ago

Indeed. Until it turns out not to be true: https://news.ycombinator.com/item?id=48541543

Alifatisk2• 1 month ago

Bummer. I fell for clickbait as usual.

eleventen• 1 month ago

A C++ ray tracer from scratch was the course project for my computer graphics class in 2016. I enjoyed the exercise immensely. Not nearly as robust as yours of course.

Quarrel• 1 month ago

I basically was ready to come on and make a snarky comment like this. "I wrote one in the '90s!".

and then I saw the examples, and the feature set. I particularly like the blender-to-Luz export.

It seems great. Good luck to OP.

Phelinofist• 1 month ago

"Without AI" is the new "Written in Rust", SCNR

tmtvl• 1 month ago

'Have you considered rewriting it without AI' seems like something I could see myself saying.

itsthecourier• 1 month ago

for the love of the game, very refreshing good ol' coding

ssenssei• 1 month ago

_" Btw this was initially coded without AI, but I've used it for the recent clean up and features. "_

???

ezekg2• 1 month ago

Wow, I also wrote a game 8 years ago and have been using AI to rebuild upon it. I'm excited to tell people that I wrote it from scratch without AI! Love these new rules!

rameerez• 1 month ago

Look at the commit history.

Out of 557 total commits in the repo, 510 have been done before the past 2 weeks. All those (minus 5 in 2023-2024) have been done on or before July 2022, months before ChatGPT had even launched.

Out of the 47 commits in the last 2 weeks, 26 were README updates / CI / docs. The remaining 21 commits are clearly cleanups, speedups, bugfixes, and tangential features like Blender import/export. Which leaves us with 505/557 commits (90%) if we're not generous --or 531/557 commits (95%) in the best case-- of non-AI commits to the repo.

OP clearly wrote most of the project by hand and has just been cleaning things up for public release the last couple weeks. Exactly as he disclosed in his comment.

wavemode• 1 month ago

To be fair, the title is "I wrote a C++ ray tracer from scratch without AI", not "This C++ ray tracer, right now, contains no AI-written code"

It sounds to me like there is some point in this project's history when both of the following were true:

1) It was a C++ raytracer

2) It was entirely human-written

So technically there is no lie here.

evilturnip• 1 month ago

Ray tracing is one of those problems that is conceptually so simple, yet continues to take so much mindshare because of all the challenges to implementation.

ivanjermakov2• 1 month ago

Me too, but in TS/WebGPU: https://github.com/ivanjermakov/moonlight

Very fun! Packing data for GPU-side BVH was quite tricky.

martiano9• 1 month ago

Wow, pretty good. Why web?

ivanjermakov2• 1 month ago

Thanks! Wanted to tackle WebGPU for making browser games.

socalgal22• 1 month ago

why not web? 1000x easier than native and 1000x easier to share

sharpfuryz• 1 month ago

Have you considered rewriting it in Rust? Not for any technical reason (I say it reflexively now)

martiano9• 1 month ago

Not really, but it would be fun. I really like Rust as well

py93• 1 month ago

Very cool!

rajhphuyal• 1 month ago

Great work on such a technically challenging project.

ddtaylor• 1 month ago

HN ongoing support and disdain for AI is perplexing.

jasonjmcghee• 1 month ago

This is (or at least used to be) a right of passage in the graphics world.

I think many people go through the very popular https://raytracing.github.io/

There was a big influx of this when Sebastian Lague did his video series on building a ray tracer.

pixelesque5• 1 month ago

And if you've decided you want to take it a bit more seriously, move on to:

https://www.pbrt.org/

which is effectively the bible, and has been for years (I wrote mine and moved into the VFX industry when the Second edition was still out! - I feel old now)

brianolson• 1 month ago

yup. me too. once upon a time that was a 2 week assignment in graphics class in college

throwpoaster• 1 month ago

Nice, I once built a ray tracer without using an SQL database.

deadbabe• 1 month ago

I think these kind of projects fail to impress these days, with or without AI.

You need a second order effect, like “I did X using this thing I built Y”, where X is the actual impressive part and the Y is just an implementation detail. Maybe like that Roman Empire Names thing.

ahoka• 1 month ago

Without AI is the new "in Rust".

chadgpt3• 1 month ago

Flagged for misleading title, since you admitted to using AI.

Show HN: I wrote a C++ ray tracer from scratch without AI

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