8 ms·

I expected they'd be either visually watching the changing contours of an opaque liquid, or somehow using refraction to get multiple visual angles of the same f

by zellyn 9y ago

I expected they'd be either visually watching the changing contours of an opaque liquid, or somehow using refraction to get multiple visual angles of the same features, but… …they're repeatedly dipping it, and using the volume displacement to reconstruct the shape. Amazing. The site is hammered right now so I can't get more details: anyone see how many dips are required to get the highest-detail models they show on the landing page?

papercrane 9y ago
In their presentation they have a bit more info. For the elephant model they show the results at 100, 500 and 1000 dips. https://youtu.be/yHvyPnkuAiw?t=1m30s https://youtu.be/yHvyPnkuAiw?t=1m30s
- zellyn 9y ago
  Ah, perfect. Thanks!
- 2_listerine_pls 9y ago
  Why is it that all voices sound monotone when presenting a SIGRAP paper.
  - npolet 9y ago
    Not everyone has loud, presentational voices.
    - caio1982 9y ago
      Well... to be fair, if you wanna make sure your study reaches as many people as possible, you must eventually need to improve your presentational skills. Like, you know, we do for everything else. I understand you didn't imply this, but IMHO there is very little pride in wanting to sound introvert forever, intentionally. Now I just hope the parent didn't say that due to misogyny.
      - seanmcdirmid 9y ago
        Voice presenting for a recording is more of a practical art than we really give credit for. Unless you do it a lot, you aren't going to be very good at it.
        annnnd 9y ago
        Which is the same as with anything else really. You need to practice to be good at something.
        seanmcdirmid 9y ago
        Yes, this is another case of the 10,000 hour rule.
  - GuiA 9y ago
    Grad students don't have much budget for voice actors. That being said, they still make efforts. When I was in grad school, I was routinely asked to do voice overs for videos that accompanied paper submissions by students who had strong accents when speaking English.
  - bsder 9y ago
    Why are all the speakers at tech conferences so bad? And why do good presenters get invited to every conference on the planet? Public speaking is a skill. It takes work and practice. Most tech folks have neither the time nor desire to do so.
    - 2_listerine_pls 9y ago
      It's copycat behavior. They are imitating other presentations.
      - Joe-Z 9y ago
        Who does? The bad one's or the good one's? Genuine question.
        bsder 9y ago
        Both. The good ones snarf ideas from other good presenters when they see something useful. A lot of bad ones imitate other presentations as the "minimum standard" because creating a good speech takes a LOT of work. I'm also going to point out that a lot of tech speakers aren't native speakers of English. If you made me, a native English speaker, give a presentation in French or Chinese, I'm guaranteed to be a bad speaker.
falsedan 9y ago
They're using computed tomography techniques, which is exactly the way I would expect.
- samstave 9y ago
  Yeah, super simple. All you do is start with a bath of water and a robot arm, then just scan the rest of the elephant! /s
  - nullc 9y ago
    Thanks for the laugh.
thearn4 9y ago
It's pretty cool. Based on the video, by dipping at various angles it looks like the process is solving an inverse problem in the Radon or Hough transform domains, something similar to what is done in medical tomographic imaging.
dkonofalski 9y ago
I just want to confirm that I understand what's going on here since you seem to get it. I have no background in this but am curious. They're dipping this thing into liquid multiple times in different ways and then measuring how much the volume has changed from the initial touch of the liquid to the volume of the object as fully submersed? Also, it seems that they are first 3D printing a 3D model, dipping, and then comparing the scan to the original 3D model? Is there any chance that the types of models they're choosing are skewing the accuracy of the results? They seem to be choosing models that don't have a lot of surface texture or much fine detail and I'm assuming that's a limit for all 3D scanning tech right now? Edit: Also, how does this thing handle 3D scanning of something like a sponge or box that might absorb the liquid? I imagine that's just not possible with this kind of scan, right?
- zellyn 9y ago
  From the video, it appears that they are dipping by 1cm, measuring volume, dipping by 1cm more, measuring volume, etc. So they end up, effectively, with a set of 1cm slices and the volume of each slice. For one orientation. Then they repeat, getting slices at a different orientation. Not only would it not work with something absorbent, but (per other comments below) does not (currently) work with shapes that trap air or catch liquid. I think they're 3D-printing test shapes because it's the simplest way to generate interesting test structures. Otherwise they'd have to manufacture (for example) a bunch of columns plus a ball using metalwork or wood or something. Some of their models look like they were originally scanned from small sculptures -- although in this day and age, it's possible they were just created as 3D models in the first place.
  - dkonofalski 9y ago
    Yeah... I just wondered why they were 3D printing things instead of getting normal, everyday objects that they could dip like keys, cups, pens, etc. I have a feeling it's not detailed enough for those use cases yet.
    - anoother 9y ago

by zellyn 9y ago

papercrane 9y ago

In their presentation they have a bit more info. For the elephant model they show the results at 100, 500 and 1000 dips. https://youtu.be/yHvyPnkuAiw?t=1m30s https://youtu.be/yHvyPnkuAiw?t=1m30s

zellyn 9y ago
Ah, perfect. Thanks!
2_listerine_pls 9y ago
Why is it that all voices sound monotone when presenting a SIGRAP paper.
- npolet 9y ago
  Not everyone has loud, presentational voices.
  - caio1982 9y ago
    Well... to be fair, if you wanna make sure your study reaches as many people as possible, you must eventually need to improve your presentational skills. Like, you know, we do for everything else. I understand you didn't imply this, but IMHO there is very little pride in wanting to sound introvert forever, intentionally. Now I just hope the parent didn't say that due to misogyny.
    - seanmcdirmid 9y ago
      Voice presenting for a recording is more of a practical art than we really give credit for. Unless you do it a lot, you aren't going to be very good at it.
      - annnnd 9y ago
        Which is the same as with anything else really. You need to practice to be good at something.
        seanmcdirmid 9y ago
        Yes, this is another case of the 10,000 hour rule.
- GuiA 9y ago
  Grad students don't have much budget for voice actors. That being said, they still make efforts. When I was in grad school, I was routinely asked to do voice overs for videos that accompanied paper submissions by students who had strong accents when speaking English.
- bsder 9y ago
  Why are all the speakers at tech conferences so bad? And why do good presenters get invited to every conference on the planet? Public speaking is a skill. It takes work and practice. Most tech folks have neither the time nor desire to do so.
  - 2_listerine_pls 9y ago
    It's copycat behavior. They are imitating other presentations.
    - Joe-Z 9y ago
      Who does? The bad one's or the good one's? Genuine question.
      - bsder 9y ago
        Both. The good ones snarf ideas from other good presenters when they see something useful. A lot of bad ones imitate other presentations as the "minimum standard" because creating a good speech takes a LOT of work. I'm also going to point out that a lot of tech speakers aren't native speakers of English. If you made me, a native English speaker, give a presentation in French or Chinese, I'm guaranteed to be a bad speaker.

falsedan 9y ago

They're using computed tomography techniques, which is exactly the way I would expect.

samstave 9y ago
Yeah, super simple. All you do is start with a bath of water and a robot arm, then just scan the rest of the elephant! /s
- nullc 9y ago
  Thanks for the laugh.

thearn4 9y ago

It's pretty cool. Based on the video, by dipping at various angles it looks like the process is solving an inverse problem in the Radon or Hough transform domains, something similar to what is done in medical tomographic imaging.

dkonofalski 9y ago

I just want to confirm that I understand what's going on here since you seem to get it. I have no background in this but am curious. They're dipping this thing into liquid multiple times in different ways and then measuring how much the volume has changed from the initial touch of the liquid to the volume of the object as fully submersed? Also, it seems that they are first 3D printing a 3D model, dipping, and then comparing the scan to the original 3D model? Is there any chance that the types of models they're choosing are skewing the accuracy of the results? They seem to be choosing models that don't have a lot of surface texture or much fine detail and I'm assuming that's a limit for all 3D scanning tech right now? Edit: Also, how does this thing handle 3D scanning of something like a sponge or box that might absorb the liquid? I imagine that's just not possible with this kind of scan, right?

zellyn 9y ago
From the video, it appears that they are dipping by 1cm, measuring volume, dipping by 1cm more, measuring volume, etc. So they end up, effectively, with a set of 1cm slices and the volume of each slice. For one orientation. Then they repeat, getting slices at a different orientation. Not only would it not work with something absorbent, but (per other comments below) does not (currently) work with shapes that trap air or catch liquid. I think they're 3D-printing test shapes because it's the simplest way to generate interesting test structures. Otherwise they'd have to manufacture (for example) a bunch of columns plus a ball using metalwork or wood or something. Some of their models look like they were originally scanned from small sculptures -- although in this day and age, it's possible they were just created as 3D models in the first place.
- dkonofalski 9y ago
  Yeah... I just wondered why they were 3D printing things instead of getting normal, everyday objects that they could dip like keys, cups, pens, etc. I have a feeling it's not detailed enough for those use cases yet.
  - anoother 9y ago