You should add a section on polarization.
Physically based rendering from first principles
61–70 of 97 posts
Re: Physically based rendering from first principles
#62Earlier quoted context omitted.
I might be a stupid question but how hard would that be to explain, and to understand? If you had to teach an alien from another universe physically based rendering: - In an exhaustive manner and, - You're only allowed to explain something if it derives from something more "fundamental" until we reach the most comprehensive physical models we have How hard would be the math behind it for example? Because realisticall…
The raw mathematics isn't the hardest; most of this is settled by the end of the second year of undergraduate physics—things like Taylor series, ODEs, PDEs, special functions, a bit of linear algebra (no proofs needed, just use the results); perhaps complex analysis which leads to Fourier transforms and all. Maybe a treatment of tensors. The issue is the sheer complexity of micro systems, and the unintuitive nature o…
> The raw mathematics isn't the hardest; most of this is settled by the end of the second year of undergraduate physics—things like Taylor series, ODEs, PDEs, special functions, a bit of linear algebra (no proofs needed, just use the results); perhaps complex analysis which leads to Fourier transforms and all. Maybe a treatment of tensors.
It sounds like the OP is saying you could tackle the article if you just know a little high school calculus and trig, and you're here saying that you need years of post-secondary mathematical education. I think you're making his case that he's dramatically simplified understanding how to compute these things for someone who doesn't have a post-secondary education.
Re: Physically based rendering from first principles
#63I'm not a fan of how people talk about "first principles" as I think it just leads to lots of confusion. It's a phrase common in computer science that makes many other scientific communities cringe. First principles are things that cannot be reduced and you have to have very good justifications for these axioms. The reason the other scientific communities cringe is because either (most likely case) it's being used im…
Thanks for the constructive criticism! A few points I'd like to discuss: Let's suppose the aim of the article was indeed to learn PBR from first principles, what would it look like? Quantum electrodynamics? I think there is merit in exploring different physical models for fun and scientific curiosity (like I mentioned in the first chapter). I (personally) feel that it's boring to just dump equations like Snell's law…
no, the first principles could be reduced to the domain that you're working in, which in this case would be non-relativistic physical optics. that is, the description of electromagnetic waves using maxwells equations. these could be considered true first principles for this problem domain.
you don't need to go to quantum physics or general relativity for everything, that would mean that a description from first principles is impossible for any field that doesn't (yet) directly connect there like biology, psychology, you name it. which may be technically correct but clearly not in the spirit of the idea.
in general this article has a quite surface level focus and narrow scope. there isn't even a description how the most common physical rendering primitive ever, a ray of light, is related to electromagnetic waves in mathematical terms. the article is not very mathematical in general which is disappointing.
Re: Physically based rendering from first principles
#64Earlier quoted context omitted.
I think Musk was the first person I noticed to really abuse this phrase. Not that it's not a useful phrase—of course it is. But it seems like it's an abuse of what should be called "core agreed assumptions" or something.
Yeah he abuses a lot of phrases... He does provide a master class on psuedointellectualism though. Drops enough vernacular that layman think he's smart and even enough that experts might think they're in good company if they don't pay too close attention. But I think the biggest clue that it's fake is how dismissive he is of nuance and detail. It's such a classic defense from psuedointellectuals because they know if…
> Meanwhile, look at any two nerds arguing. It's always nuanced and over minute things that they'll always insist are very important (because often it is, but only at that level).
Sorry, but no, nerds are huge bikeshedders, and often miss the forest for the trees. I think this also explains how dismissive you are of experts who have actually worked with Musk and don't seem to share your low opinion of his expertise in certain areas. Often the importance of nuance is overblown, as it typically only has third or fourth order effects that can be ignored in favour of focusing on the first and second order factors that dominate.
Re: Physically based rendering from first principles
#65The discussion of the difference between metal and non-metal is a bit unclear. When he says that metal has no "diffuse reflection" but non-metals do, I think what he might mean is that metals have no subsurface scattering. Rough (not mirror-like) reflections do certainly also look "diffuse".
Re: Physically based rendering from first principles
#66Earlier quoted context omitted.
Yeah he abuses a lot of phrases... He does provide a master class on psuedointellectualism though. Drops enough vernacular that layman think he's smart and even enough that experts might think they're in good company if they don't pay too close attention. But I think the biggest clue that it's fake is how dismissive he is of nuance and detail. It's such a classic defense from psuedointellectuals because they know if…
> Meanwhile, look at any two nerds arguing. It's always nuanced and over minute things that they'll always insist are very important (because often it is, but only at that level). Sorry, but no, nerds are huge bikeshedders, and often miss the forest for the trees. I think this also explains how dismissive you are of experts who have actually worked with Musk and don't seem to share your low opinion of his expertise i…
> I think this also explains how dismissive you are of experts who have actually worked with Musk and don't seem to share your low opinion of his expertise in certain areas.
It is difficult to get a man to understand something, when his salary depends on his not understanding it.
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I think there's also something of a "gell-mann amnesia" effect going on here. I could buy him being a manufacturing genius or whatever for a while because I know nothing about car or rocket manufacturing. But as soon as he bought twitter, I realized he was an absolute moron who had never built or successfully software himself in his life (or perhaps his brain had simply severely atrophied since his time at PayPal to the point he should be aware), but wanted to sling buzzwords as if he were a coder.
Re: Physically based rendering from first principles
#67Fantastic
Re: Physically based rendering from first principles
#68How was the interactivity achieved? Could you maybe link to the source so I can learn? I have been trying to get something like this working with quarto, but it is getting way too complicated.
I wrote everything from scratch in javascript and webgl. You can check the entire source code of the article here: https://imadr.me/pbr/main.js Beaware though, it's a 8000+ lines of code js file that is very badly organized, it's by no mean a reference for good quality code. However I find writing everything by hand easier in the long term than using already existing libraries for example. The code includes all the m…
Love it! For typescript, esbuild has been my favorite tool for turning typescript into browser-readable js, and then I check type errors separately using the ide plugin.
Re: Physically based rendering from first principles
#69Earlier quoted context omitted.
It isn't just computer science people that do this, either. My gut is it was a common thing in MBA style classes as a way to approach a topic in a field you are not expert in. Specifically, it is common among management talkers, from my experience. I think the idea is supposed to be to go back to the "first principals [that you would have been taught]." Which, yes, sometimes you will learn things that show these earl…
I think >90% of the time I hear the phrase "first principles" mentioned I'm safe in expecting something that is very high level to follow. I'm glad nerds have (kinda) been pushed into celebrity status but I also think there's a lot of cargo culting that has followed. Unsurprising I guess, since one is much easier than the other. I just wish there was more pushback, especially in tech (not because the only abuser of t…
Right, this is why I think people assume "first principals" means "first [learned] principals." It is almost always super high level and used synonymously with "back to basics."
And fully agreed on your reasoning on why these are good phrases to keep in mind. I think I would pile on to the "becomes an iterative process" to highlight that "starting from first principals" is more likely to be where folks start. With advanced solutions expanded to cover more and more details that the initial assumptions could gloss over.
I think this is largely justified, if only because "first principals" meaning "absolute foundation" are almost certainly still being discovered.
Re: Physically based rendering from first principles
#70Earlier quoted context omitted.
I think Musk was the first person I noticed to really abuse this phrase. Not that it's not a useful phrase—of course it is. But it seems like it's an abuse of what should be called "core agreed assumptions" or something.
Lol apparently reasoning by analogy is first principles to him -- see human drivers using only vision therefore no lidar somehow being "first principles".
Maybe I missed it, but I've never seen him claim that using only vision is "first principles" thinking. However, relying only on vision can make sense once you realize that roads and signage and everything is literally designed around vision. Any system that does not prioritize vision cannot deal with unexpected obstacles, like new signage. If your vision is good enough to see obstacles and understand signage, the added usefulness of lidar relative to the cost seems pretty low, and if you don't have vision and have only lidar, then your system will not be flexible enough, and if you have lidar and vision, then your system will be more expensive than a system without lidar.