Live data from Hacker News

Edge detection doesn’t explain line drawing

aaronhertzmann.com

131–140 of 174 posts

Re: Edge detection doesn’t explain line drawing

#131
post #87

Earlier quoted context omitted.

There is one key difference between reality and simulation. In reality you have to spend energy to remove noise. In simulation you have to spend energy to add noise. Or perhaps more accurately, all objects interact in reality and energy needs to be spent to prevent interaction, while simulation requires energy to make objects interact. But it’s even worse than it sounds at first, because you need to spend energy not…

Perhaps a foolish question but does “simulation” necessarily imply calculation or is that just an extension of our current evolution of computing technology as an analogy for what a simulation would be? I’m not convinced the one necessitates the other.

Oh, I don’t know. I mean conceptually a simulation is just a model that changes over some axis, time being a prime candidate. I’ve seen some goofy models that use an axis other than time to create some interesting visuals. There are definitely game makers playing with some of this stuff.

Calculation may be the wrong word for what’s necessary for a simulation, but I don’t think you can have a simulation without something analogous to computing. But the computation may look foreign, think analog vs digital computers. I mean, what would it mean to simulate something if you weren’t interested in finding some measurable thing? How do you seperate the ability to observe the simulation and not be able to measure anything? I may be too steeped in engineering to be able to answer this, since the last thing I simulated was an analog circuit. But I also studied artificial life, and even there the goal was to learn something about life.

Re: Edge detection doesn’t explain line drawing

#132
post #94

Eh. To me it looks like the authors extends "lines-as-edges" explanation of why we can understand line drawings to the claim that the visual cortex works almost only on edge detection, which is obviously bunk and so easily refuted by him. Then later he shows a shillouette image we can understand even though the edges themselves are not understandable, and somehow this is supposed to be evidence against lines as edges…

The word is spelled "silhouette".

Re: Edge detection doesn’t explain line drawing

#133
post #35

Earlier quoted context omitted.

> Calling an image a "representation" or saying that it "has a liking" to the real thing is sort of begging the question. The question to be answered is: "In what way is it a representation? Represenation or having-a-liking is not some hazy notion though. It means there are things in our drawing that map to how those things are in the actual thing. And there are: edges, proportions, shapes. But it's not some close ma…

> That is, a drawing doesn't have to follow the actual edges of the thing depicted with any accuracy for it to be recognized as such This is literally what this link is about, but you do still recognize that there is are "why" and "how" questions to be answered here?

Yes, just not the why and how questions the author asks, or the way he phrases them...

Re: Edge detection doesn’t explain line drawing

#134

Earlier quoted context omitted.

Perhaps a foolish question but does “simulation” necessarily imply calculation or is that just an extension of our current evolution of computing technology as an analogy for what a simulation would be? I’m not convinced the one necessitates the other.

Oh, I don’t know. I mean conceptually a simulation is just a model that changes over some axis, time being a prime candidate. I’ve seen some goofy models that use an axis other than time to create some interesting visuals. There are definitely game makers playing with some of this stuff. Calculation may be the wrong word for what’s necessary for a simulation, but I don’t think you can have a simulation without someth…

What I wonder about from your explanation is how does a simulation know where the noise is coming from. I feeling is that inside the simulation one is unable to differentiate the source of the noise.

Re: Edge detection doesn’t explain line drawing

#135
post #81

Earlier quoted context omitted.

How could at least two cultures without a communication line between them both come up with such a quirky idea? There must be some underlying truth to it.. I'm sold. World turtle is the answer.

"The Turtle Moves"!

I'm sure they stepped on turtles to go back and forth across the bering strait.

Re: Edge detection doesn’t explain line drawing

#136
Huh, right up my alley... a while back I was playing with trying to turn photos into sketches ( https://hachyderm.io/@bazzargh/109928618521729073 ); one of the effects I found really noticeable with my super-naive approach was that it tended to overemphasise very dark areas in a way we don't see.

Then last week I saw this, which also does some fill in shading (but, using ML)-worth the click, it's a project that makes it appear as if paper held over an object causes it to be sketched...but in fact it's all post-processing... https://www.youtube.com/watch?v=vArIkzYtW6I

This got me back to wondering about the shading problem, and I ended up down a rabbithole reading papers like https://www.yorku.ca/rfm/pub/2021annrev.pdf (review article on state of the art), https://www.frontiersin.org/articles/10.3389/fpsyg.2022.9156... (recent markov model, with links to code) about lightness and brightness perception, and how our mental model of how the scene is lit can explain a bunch of optical illusions.

While I was going for a charcoal effect, this approach https://openprocessing.org/sketch/486307 - scribble using brightness as 'gravity' on the pen - is pretty nice.

Anyhoo, I'm not going to critique the article, because I'm a total amateur just doing this for fun, but it _is_ fun, and very satisfying when you get the computer to draw something that looks hand drawn instead of just a sobel filter.

Re: Edge detection doesn’t explain line drawing

#137
post #87

Earlier quoted context omitted.

I believe the universe we live right now is no different than a simulation. Subtle difference in belief but I think it might have a big implication.

There is one key difference between reality and simulation. In reality you have to spend energy to remove noise. In simulation you have to spend energy to add noise. Or perhaps more accurately, all objects interact in reality and energy needs to be spent to prevent interaction, while simulation requires energy to make objects interact. But it’s even worse than it sounds at first, because you need to spend energy not…

I think the reality as simulation camp gets one thing right - reality is virtual. Space and time don't exist, there is only information and relation.

Re: Edge detection doesn’t explain line drawing

#138
post #16

Earlier quoted context omitted.

ah, someone who paid attention in lecture! (incidentally; there’s a fairly deep literature of historians of science that have carefully documented that we describe ourselves as analogous to the most sophisticated technology of the day: see “to lose one’s temper”, “to blow a gasket”, “i got my wires crossed”, “sorry, cache miss”, … as metaphors and idioms of mental state through the centuries that reflect the cool tec…

And also the universe itself is often seen through the lens of contemporary technology. Are we living on an island that floats on a giant turtle’s back? Or are the heavens like giant clockworks? Or maybe it’s all a computer simulation? These cosmological speculations are separated by thousands of years, but they are all simply a reflection of what the person finds most awe-inspiring in their everyday life.

Each of these are true in a sense. There's no turtle, but we are living on an "island" floating through space. The heavens do follow predictable, clockwork rules. Computer simulations are at least a good way to describe the universe.

Re: Edge detection doesn’t explain line drawing

#139
post #37

Earlier quoted context omitted.

The upscaled image stores more information than the original image, so it must be possible to keep all the information while still doing edge enhancement!

Stores more data, but the same information, and if there is any interpolation then some of the data is modified, meaning that you lose a little data. In fact even without interpolation I think you change the data. If you imagine a hard edge that aligns with a pixel [ ] boundary then you imagine upscaling in various ways, I think it's QED. You change data about the sharpness of the edge. [ ] I use an Android phone, wi…

Well consider nearest neighbor upscaling. Since we are upscaling, every pixel in the source image will determine one our more pixels in the result image. Consider one of the source pixels that turns into multiple result pixels. If you manipulate one of those while leaving the other(s) intact you can still recover the source image (assuming you know which pixels are still good), meaning no data was lost.

Re: Edge detection doesn’t explain line drawing

#140

Earlier quoted context omitted.

A manager once told me he'd never hire a PhD because once they complete the specialized work we hire them for, they inevitably get put on something outside their specialty - like your linked xkcd - and then their acceptance as experts along with that behavior causes real problems. Another time I had an older PhD moved to my area (outside his) where we were trying to meet a number of objectives. He said in a meeting t…

Yeah, bad PhDs, bad! Edit: People being arrogant or know-it-all is probably not especially correlated with having obtained a PhD, but more with overall frame of mind, and I find this comment to be a uselessly negative ad-hominem.

Sorry, but I think it's correlated in two ways. One is that very bright people, which I think includes most PhD-havers, are especially used to being right. When they have the rare experience of being ignorant and wrong, they may struggle with it much more than others. Two, academia is a bubble. I think that's great; I love that we have a place where people who are deeply interested in something can focus entirely on that. But it necessarily means that they're less likely to know about things outside that bubble.

That's not to say it's a perfect correlation. I know plenty of people with PhDs who don't have the problem in the XKCD cartoon. But I too am careful hiring PhDs in tech jobs. Professional work is just very different than academic work. It takes time to learn it for people whose main focus is the theory. After all, "In theory, theory and practice are the same. But in practice..."

Post reply on HN