[HN Gopher] 3D printed mirror array
       ___________________________________________________________________
        
       3D printed mirror array
        
       Author : agmm
       Score  : 991 points
       Date   : 2021-11-11 19:17 UTC (1 days ago)
        
 (HTM) web link (github.com)
 (TXT) w3m dump (github.com)
        
       | xmonkee wrote:
       | This is so adorable
        
         | matmatmatmat wrote:
         | Seriously, can it get much better than this?
        
           | zardo wrote:
           | It should be possible to do animation driven by the movement
           | of the sun in the sky.
        
             | tdeck wrote:
             | Similar to a digital sundial
             | https://en.wikipedia.org/wiki/Digital_sundial
        
       | nazgul17 wrote:
       | Fantastic! I love the creativity that went into this.
        
       | zw123456 wrote:
       | Archimedes would be proud! And you should be too!
       | 
       | Congrats, and thank you so much for sharing this, it totally made
       | my day.
        
       | bmsleight_ wrote:
       | Wow how wonderfully geeky romantic. Did he say yes ? [Edit the
       | sand said yes!]
        
       | matteosb wrote:
       | This reminds me of company called Leva.
       | 
       | Check out this project https://www.leva.io/projects/kinetic-wall
        
       | tarikozket wrote:
       | hats off
        
       | jhgb wrote:
       | I'm wondering if a similar effect couldn't be done using a
       | continuous surface and just silvering it. I saw something similar
       | done with refraction but can't remember the URL now. 3D printers
       | definitely have higher resolution than mirrors of this size.
        
         | jacquesm wrote:
         | If you're willing to spend a lot of money on silver then
         | probably yes. After all the height differences are substantial
         | and silver isn't cheap. 3D printers resolution sucks in
         | comparison to the mirrors, I'm not sure what you mean by that.
        
           | jhgb wrote:
           | Not quite sure you need _that_ much silver. You need some
           | filler between the silver layer and the crude plastic surface
           | to get the silvering smooth, but that filler doesn 't
           | necessarily need to be silver. As for the resolution, I'm
           | judging it from this picture:
           | https://raw.githubusercontent.com/bencbartlett/3D-printed-
           | mi... - there seems to be almost two orders of magnitude of a
           | difference between the size of a flat mirror and the size of
           | the "printing step".
        
           | Turing_Machine wrote:
           | Aluminizing it would be way cheaper than silver.
           | 
           | For that matter, you could probably glue down pieces of
           | aluminized mylar rather than using mirrors, since you all you
           | need is a spot of light, not a full-blown mirror image.
           | Aluminized mylar is pretty cheap!
        
             | jacquesm wrote:
             | Bare aluminum would oxidize in a very short time to
             | something dull. It would still reflect light but not quite
             | as good.
             | 
             | Aluminized Mylar would definitely work, but that's not bare
             | aluminum but aluminum with a shiny layer over it to keep it
             | clean.
             | 
             | Very useful stuff, I built huge solar concentrators with
             | it. 1000 suns on an area the size of a poststamp. You can
             | do some pretty crazy stuff with that kind of energy
             | density.
        
               | kragen wrote:
               | You might need a micron of thickness of aluminum or
               | silver. This piece looks like it's about 300 mm x 300 mm,
               | which would work out to 90 mm3 of silver (or aluminum),
               | which at 10.5 g/cc would work out to 950 mg of silver.
               | Silver currently costs US$25.25 per troy ounce, so this
               | would be 0.12C/ (US$0.0012) of silver, or somewhat less
               | of aluminum.
               | 
               | Both silver and aluminum will tarnish if exposed to the
               | air, silver more slowly but much more completely.
               | 
               | The process for silvering things is a lot easier to do at
               | small scales than the process for aluminizing them.
               | Aluminizing things normally requires a fairly good
               | vacuum, and, moreover, a vacuum chamber large enough to
               | fit whatever you're aluminizing. Perhaps someone will
               | come up with some kind of convenient wet process for
               | doing it but I'm not hoding my breath.
               | 
               | By contrast, you can silver glass with Tollens' test,
               | using distilled water, silver nitrate, concentrated
               | aqueous ammonia, hydroxide of potassium or sodium, and a
               | reducing sugar (almost any sugar that isn't sucrose, for
               | which you can substitute numerous other chemicals, such
               | as formaldehyde, formate, isopropanol, or tartrate). This
               | is commonly done as a classroom demonstration in
               | chemistry labs nowadays, and it was done on a large scale
               | almost 150 years ago for telescope mirrors. Nitric acid
               | is beneficial but, unless you have to make the silver
               | nitrate, not essential.
               | 
               | This is why it's much more common for amateur telescope
               | makers to silver their mirrors rather than aluminizing
               | them.
        
               | jacquesm wrote:
               | I've silvered a lot of copper plates for photography
               | (Daguerrotypes).
        
           | numpad0 wrote:
           | There are single solution spray-on electroless plating
           | "paint" for modelmaking. They can make any smooth and black
           | surface into a mirror so I think it's just a matter of
           | surface preparations.
        
             | michaelt wrote:
             | Can they actually produce a mirror you could mistake for a
             | glass mirror?
             | 
             | I assume if your mirror is "only" as good as as the shiny
             | side of some aluminium foil, you can't project things with
             | any detail.
        
               | numpad0 wrote:
               | Isn't the mirror surface effectively at the aperture in
               | this system...
        
         | itronitron wrote:
         | You could use reflective mylar tape over the surface. And if
         | you wanted something with very high resolution I'd try vacuum
         | forming wide mylar film onto the 3D printed surface.
        
         | perlgeek wrote:
         | I don't think so; the angling of the mirrors is done with small
         | steps, which the mirrors smooth out.
         | 
         | If you apply a very thin film, it will just follow the steps.
        
       | jcmontx wrote:
       | Cool af! Congrats
        
       | blunte wrote:
       | Nice. Now step 2: individually articulated mirrors :)
        
       | colinmegill wrote:
       | Congrats! Wonderful!
        
       | jstanley wrote:
       | Excellent. I wonder how practical it would be to put each mirror
       | on a servo so that you can change the image in real time?
        
         | mrnotcrazy wrote:
         | https://www.youtube.com/watch?v=WwCmzwSE98o&list=RDCMUCUbDcU...
         | I don't know if you would need a server for each mirror? but
         | you would need.... two axis of rotation? and making a
         | mechanical system that slowly moved mirror by mirror to update
         | the position might be more complex.
        
         | [deleted]
        
         | ortusdux wrote:
         | Depends on the desired scale -
         | https://www.youtube.com/watch?v=9nb8mM3uEIc
        
           | nomel wrote:
           | This is quite a bit different. DLP like projectors are
           | binary: straight forward or somewhere away. The layout of the
           | grid of mirrors matches the layout of the dots you can
           | illuminate, in the image. Something like OP has would require
           | some pretty serious angular precision.
        
             | beecafe wrote:
             | You could use holography/beamforming to steer a beam from a
             | DLP, although it would be just a small % of the original
             | power.
        
               | nomel wrote:
               | I think the beautify of the mirror system is that it's
               | direct, understandable/observable, and nice to look at by
               | itself, even if it's not showing an image. It's elegant.
               | If you use beam formers and DLPs, you're just making an
               | overcomplicated DLP projector that's going to look like
               | an overcomplicated DLP projector.
        
               | beecafe wrote:
               | Absolutely. And it'll keep working on a sandy beach far
               | from any power source.
        
         | jjk166 wrote:
         | You'd probably want to use galvos instead of servos for this
         | application (high speed/precision, low load mass).
        
           | jacquesm wrote:
           | Or piezo.
        
         | martinky24 wrote:
         | Look up "Adaptive Optics". That's literally what you describe
         | :) They've got a somewhat niche use in astrophotography.
        
         | regularfry wrote:
         | Almost trivial, if you're prepared to make the mirrors a bit
         | bigger. I've got a 7-element array on my workbench right now.
         | You want two servos per mirror, one for each axis. I'm using
         | flexures for linkages between the servos and the mirrors, and
         | universal joints made of magnets and ball bearings to hold
         | everything together. The mirror tiles I'm using are 110mm
         | across, flat-to-flat, which are bigger than this example, and
         | that makes layout and assembly straightforward in a way that it
         | wouldn't be if everything was smaller. Everything's printed in
         | PETG, raspberry pi pico for brains driving a pca9685 PWM driver
         | over i2c. The linkage geometry is the only hard part, the CAD
         | and printing was pretty much a one-weekend project.
        
           | regularfry wrote:
           | Should probably point out that with 2 servos per mirror you
           | can match surface normals but not surface offsets. You can
           | make each individual mirror match the gradient of a curve,
           | but you can't make a curve like the parabolic dish in the
           | GitHub link without a third servo per mirror. I'm waiting for
           | more parts to arrive for that...
        
         | anfractuosity wrote:
         | You can get MEMS microscanners although they're probably a bit
         | small - https://en.wikipedia.org/wiki/Microscanner but they can
         | orientate a mirror on two axes.
         | 
         | This one looks a pretty decent size -
         | https://www.sercalo.com/products/mems-mirrors/mm160110-2
        
           | jacquesm wrote:
           | Swiss made precision optical gear. I think the price of that
           | little mirror just might make your head spin.
        
       | wopsahl wrote:
       | Has anyone seen the mirror array that was built with
       | ~2"X2"stainless steel mirrors that are attached to a sheet of
       | blue spring steel that was laser cut as a compliant mechanism for
       | each mirror so when an offset wheel on a threaded bolt behind the
       | mirror is turned it progressively tilts the mirror from a minimal
       | angle to a maximum angle? Each bolt was then driven using a
       | single stepper motor(one mirror adjustment motor for the whole
       | array, kind of a budget build, instead of one motor per mirror)on
       | a belt driven x-y frame. The mirror array was positioned
       | horizontally 2' off the floor of a museum with works of art, a
       | camera is then pointed at an angle near eyelevel probably 20'
       | away from the array. Then you choose an art work and the mirrors
       | are rotated through their angles and when that pixel(mirror)
       | reflects the color back to the camera that matches the art work
       | you chose it stops moves to the next mirror and then repeats
       | until there is a full image made of reflected light. Obviously
       | the final image is pixelated but roughly resembles the original
       | work. I saw this years ago and can no longer find any of it
       | online. I've tried every search combination I could think of.
       | Some of these details might be wrong but I'm just going off
       | memory here. Pls help
        
         | tdrdt wrote:
         | I have been thinking about this for some time: cylinders each
         | attached to a motor. The glossy end of the cylinders is cut at
         | an angle. The rotation of each cylinder dictates from which
         | direction light is reflected.
        
         | snypher wrote:
         | It sounds like a Danny Rozin piece
         | 
         | https://en.wikipedia.org/wiki/Danny_Rozin
         | 
         | Edit; I'm sure it could be
         | https://www.smoothware.com/danny/mirrorsmirror.html
        
           | wopsahl wrote:
           | These are close but it was definitely horizontal these are
           | vertical. Thank you for the links!!
        
       | nikkinana wrote:
       | That's sweet except he's a faggot.
        
       | [deleted]
        
       | dcroley wrote:
       | This idea looks like something you could commercialize!
        
       | _Microft wrote:
       | I might be getting old but this is the sort of magic by
       | technology I would like to see more of in the world instead of
       | using tech to try putting people into fake worlds in some
       | metaverse.
        
         | gnramires wrote:
         | I don't think the particular metaverses available right now
         | seem that good, but I don't share the consistent prejudices
         | against virtual reality. Why is real reality any better? You
         | can build awesome stuff in virtual reality as well (in fact,
         | you can build almost anything imaginable, at a much lower
         | cost).
         | 
         | Keeping in touch with reality is extremely important (because
         | we are bound by its rules after all), but virtual existence has
         | enormous potential as well :)
         | 
         | (that can't be realized, and certainly not realized for
         | everyone, in the world of atoms -- virtual reality is
         | delightfully egalitarian)
         | 
         | Value the bits _and_ atoms!
        
           | spijdar wrote:
           | Just a thought, but one reason to be skeptical of virtual
           | reality, if only out of pragmatism, is that unlike "real"
           | reality, virtual reality is trivially controllable by single
           | entities.
           | 
           | Maybe not an intrinsic limitation, but for the foreseeable
           | future, VR = a domain where some entity like Facebook is
           | effectively omniscient and omnipotent.
        
           | r00fus wrote:
           | VR is a better mousetrap to keep people engaged and connected
           | (two things FB values a lot as it drives revenue).
           | 
           | What real-world problems does VR serve for the average FB
           | user? Or anyone frankly?
           | 
           | Meanwhile, 3D printing could greatly improve how we design
           | and fabricate things people use every day.
        
         | [deleted]
        
         | ampdepolymerase wrote:
         | There is nothing special about this. This is the basis of all
         | MEMS technology used in lidar. Some VR goggle designs probably
         | contain MEMS parts too. It is disingenuous to complain about
         | the metaverse business model while oohing and aahing over the
         | exact same technology used to implement it.
        
           | dang wrote:
           | Can you please not post in the flamewar style to HN? We're
           | trying to avoid flamewars here, and I'm sure you can make
           | your substantive points without that.
           | 
           | https://news.ycombinator.com/newsguidelines.html
        
             | TheRealNGenius wrote:
             | I mean, I don't think the parent post was that substantive
             | either. There is nothing in this submission that
             | necessitates roping in the topic of the metaverse. They
             | could have just left it as they found this tech
             | interesting.
        
               | jacquesm wrote:
               | If you can't say something nice about a project like this
               | then say nothing at all. To belittle it is classless.
        
               | TheRealNGenius wrote:
               | true
        
               | Turing_Machine wrote:
               | Agreed. I really, really hate it when someone shares
               | something cool they've made and HN people dump on it.
               | 
               | I'm not saying that HN has to be all mindless
               | cheerleading, but non-constructive criticism is not
               | helpful to anyone (except the critic's ego, maybe).
        
               | dang wrote:
               | Sure, but there are degrees of these things. The GP
               | comment was generic, which does have a bad effect on
               | discussion (it evokes shallower and often nastier things
               | from others), but the comment I replied to took things a
               | few notches further.
        
       | ape4 wrote:
       | The wedding is going to be over the top
        
         | a_lost_needle wrote:
         | Well, it definitely looks like it will be pretty gay! :)
        
       | CTDOCodebases wrote:
       | Such a cool idea. Now you have a momento to remember the day that
       | can be hung on a wall.
        
       | mrfusion wrote:
       | I was going to suggest you could use it as a home decoration to
       | make a message everyday but it would only work one day a year?
        
         | saboot wrote:
         | You'd need the mirror planes to be adjustable in the XY tilt
         | directions. Seems doable though, would be a cool next project
        
           | enchiridion wrote:
           | Or not? That's an interesting challenge. Multiple messages
           | depending on the light angle
        
             | ansible wrote:
             | Sort of the opposite of a digital sundial:
             | 
             | https://www.thingiverse.com/thing:1068443
        
         | fudged71 wrote:
         | It's possible to create artificial light with parallel rays
         | like the sun, you just need a parabolic dish mirror. So in
         | theory yes you could do this at home for everyday projections,
         | just not with the sun.
        
       | totetsu wrote:
       | Now how could we achieve the same thing with just origami?
       | https://jwst.nasa.gov/content/features/origami.html
        
       | tomaskafka wrote:
       | At a risk of spoiling a startup idea, I'd love a set of motorized
       | mirrors I could put on a roof of a house on the other side of the
       | street from me, that would send sunlight to the eastern side of
       | my flat during the afternoon :).
        
         | mym1990 wrote:
         | It's like the Uber of renting other peoples roofs! (I've been
         | watching way too much shark tank the past 3 days...)
        
       | YXNjaGVyZWdlbgo wrote:
       | I would love an array of them in the style of old airport
       | signages could be an amazing effect. Great work.
        
       | diplodocusaur wrote:
       | There is an artist (at least) that uses arrays of motorized parts
       | to create a similar effect
       | https://www.youtube.com/watch?v=kV8v2GKC8WA mesmerizing
        
         | qwertox wrote:
         | Thank you for linking this.
        
         | djmips wrote:
         | These isn't a similar effect but your link is very cool. I
         | think the magic here is a static array of mirrors printed to
         | create an image on another surface from multiple reflections of
         | a bright source light.
        
         | mlok wrote:
         | This is quite close too : https://prusalab.cz/projekty/reflexe/
         | 
         | (Petr Vacek & Adam Cigler / Prusalab / Czech Republic)
        
           | m4rtink wrote:
           | I saw this on an industry fair and even spoke with one of the
           | authors - its very impressive and cleverly done + they are
           | continuously improving it. :)
        
             | mlok wrote:
             | I also had the chance to see it, and I agree with you :
             | impressive. Glad to know it is still evolving.
        
         | mygoodaccount wrote:
         | Who is on the Cover of WIRED 1999? Can someone please find out.
        
         | matteosb wrote:
         | check out this as well https://www.leva.io/projects/kinetic-
         | wall
        
         | mym1990 wrote:
         | I've always been interested in making large works of art out of
         | many many small things(LED cubes, wooden blocks, etc...). Would
         | love to explore these kinds of things more
        
         | abrookewood wrote:
         | That's fascinating - the artist does everything himself from
         | fabrication to design. Looks incredible.
        
         | jonahx wrote:
         | "The electronics and the mechanics and the fabrication took me
         | a year. Then it took me an afternoon to program the computer to
         | actually activate it"
        
           | arketyp wrote:
           | No knock on the artist, I particularly like the pom-pom
           | display, but I get the sense that much of art today is about
           | going roundabout ways, almost Rube Goldberg machine like, to
           | achieve things could be presented in other ways with minimal
           | effort. Sometimes this alternative mediation is interesting,
           | but sometimes it almost feels dismissive of the metaphysical
           | magic that is computing.
        
             | berkes wrote:
             | A lot of art is about "the process".
             | 
             | I mean, the resulting painting as done by Pollock or
             | Mondriaan is pretty silly. Just splash some paint in a
             | canvas, or draw some lines and use the "fill bucket tool"
             | to create colored squares, right?
        
               | arketyp wrote:
               | Yes, sure, it's about the process and about the
               | inescapable context with postmodern conceptual art.
               | Whether it's mere splashes I will leave aside, but
               | Pollock and Mondrian precisely brought the consideration
               | of the process to a new light, that's part of what makes
               | them significant figures. Mondrian didn't have
               | mspaint.exe, those geometries meant something different
               | at the time. Also, I don't think Picasso would have been
               | so infatuated by cubism if computers with triangle mesh
               | rendering and solid modeling had been around.
        
       | thanatos519 wrote:
       | Awesome! It's like a giant static DLP chip!
        
         | diplodocusaur wrote:
         | You are correct! This is essentially how office projectors work
         | https://youtu.be/KpatWNi0__o?t=102
        
       | Turing_Machine wrote:
       | Very cool.
       | 
       | In a less-artistic application, you could use this idea to print
       | multiple sections that could be assembled to make a large pseudo-
       | parabolic mirror for a solar concentrator. You wouldn't get
       | telescope-quality imaging, certainly, but if all you needed was
       | to concentrate a lot of light on a small space (for a steam
       | generator, say) it should work fine.
       | 
       | Congrats on the upcoming wedding!
        
       | quickthrower2 wrote:
       | This made my day! Nothing technical to say sorry!
        
       | fgblanch wrote:
       | This project is soooo amazing! Congrats! Great piece of art and
       | engineering
        
       | intrasight wrote:
       | I wonder if rather than "additive" you could do similar with
       | "subtractive" fabrication. Take a wooden board and cnc mill and
       | cut circles on the surface at the appropriate orientations.
        
         | ruined wrote:
         | generally it's just a matter of slicing the same source STL
         | file to the appropriate gcode, but in this case the particular
         | geometry (lots of sharp concave angles) seems more suited to
         | additive manufacturing.
        
         | serf wrote:
         | yes, but it'd require a redesign or very special tooling.
         | 
         | that spacing between each mirror 'pedestal' is fairly deep,
         | it'd require a very long end-mill or a five axis machine to be
         | able to get into those crevices.
         | 
         | it'd be trivial to carve the needed angle into each 'mirror
         | pedestal' , but the current design doesn't support the premise
         | very well.. still, doable.
        
           | intrasight wrote:
           | How about this approach. Just have a collection of wooden
           | dowels with one end milled to be concave at one of 20 or 30
           | angles. Then you can assemble whatever mirror array you want
           | by selecting and positioning the appropriate dowels. Or sold
           | as a kit made out of plastic hex shaped rods that snap
           | together.
        
       | meigwilym wrote:
       | > that could just bring this idea into existence from nothing but
       | a bit of code and some basic principles of physics.
       | 
       | You're putting yourself down here. But congrats on the proposal!
        
       | Jimmc414 wrote:
       | I'm wondering how feasible it would be to repurpose this code for
       | a concentrated solar power setup.
        
       | chilling wrote:
       | Absolutely mesmerizing work!
        
       | HarHarVeryFunny wrote:
       | Cool! Makes a nice object to hang on the wall too!
       | 
       | I wonder if there's any types of filament that could be used to
       | print a mirror-like surface good enough to work ?
        
       | milofeynman wrote:
       | What happens if you point all the mirrors at the same spot? Fire?
        
         | primitivesuave wrote:
         | Archimedes famously used mirrors to burn a fleet invading
         | Syracuse: https://en.wikipedia.org/wiki/Burning_glass
        
       | dukeofdoom wrote:
       | Did you try sinking any ships with this?
       | https://en.wikipedia.org/wiki/Burning_glass
        
       | jcun4128 wrote:
       | That's mad creative, like those solar clock things
        
       | jmd42 wrote:
       | This rocks, and congrats!
        
         | mhb wrote:
         | Did he say yes?
        
       | jonas21 wrote:
       | Bears a striking resemblance to the James Webb Space Telescope
       | 
       | https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
        
       | ttrbls wrote:
       | https://bit.ly/3kvet7n
        
       | azinman2 wrote:
       | This is very cool. Perhaps I'll similarly do a writeup of my
       | nerdy marriage trick -- I created custom 3D chocolate bars with
       | our faces on them to hand out to guests. It required a ton of
       | iteration and a lot of chocolate work (which is really hard!),
       | but was really special in the end.
        
       | akomtu wrote:
       | This idea will have many unexpected applications. For example
       | difficult to remove signs projected to flat surfaces.
        
         | makeitdouble wrote:
         | An application close to this idea: IKEA arrow signs projected
         | on the floor.
         | 
         | They need no painting, floor needs no protection or treatment
         | and they won't disappear until the light is off.
        
           | zestyping wrote:
           | You can do that just with a mirror in the shape of an arrow.
           | Or a mirror with a negative arrow painted on it :)
        
             | makeitdouble wrote:
             | Yes. It's pretty interesting they went the "projector" way.
             | 
             | I guess there is an issue of the arrow not being lit enough
             | to stand out if the mirror flatly reflects ambient light,
             | it would need to focus a lot more light, which would also
             | make it much bigger.
             | 
             | It might also be that the additional light from the arrow
             | is just beneficial in that specific case.
        
       | harvie wrote:
       | This is future of the street art. Mount it using liquid nails to
       | some place that is hard to access and point it somewhere where
       | lots of people will see it during rush hour.
       | 
       | Eg.: You can install it in such way that parliament building will
       | get defaced every day during lunch hours by mounting on near
       | building or tall lamp post. Or maybe put it on your own roof,
       | that way nobody can remove it :-)
        
         | thih9 wrote:
         | > put it on your own roof, that way nobody can remove it
         | 
         | I imagine you'd need a permission; just like you'd have to get
         | one if you wanted to use a projector and project something onto
         | parliament. (TINLA)
        
           | Mountain_Skies wrote:
           | One of my friends used to live across the street from a
           | federal courthouse. He tried projecting a movie from his
           | window onto a blank wall of the courthouse. Half an hour
           | later several LEOs were at his door asking him "politely but
           | firmly" to turn off the projector and to never do it again.
        
         | 123pie123 wrote:
         | like the idea but how much sun does london really get?
        
           | hobofan wrote:
           | Enough to allow a skyscraper to melt cars[0].
           | 
           | [0]: https://www.bbc.com/news/uk-england-london-23930675
        
             | jacquesm wrote:
             | That's a bit of a special case though, at 50 suns or so it
             | doesn't require much for that effect. Great demo for solar
             | concentrators though!
        
         | Toxygene wrote:
         | Word of warning:
         | https://en.wikipedia.org/wiki/Aqua_Teen_Hunger_Force#2007_Bo...
        
           | sanj wrote:
           | That piece was done by my (then) neighbor.
           | 
           | It was a little unnerving to come home to a dozen black
           | Suburban SUVs parked in front of my house.
        
             | dylan604 wrote:
             | What have you been up to that would lead to such an
             | unnerving response? ;-)
        
               | mellavora wrote:
               | That's not the unnerving part (answer would be "probably
               | nothing"). The unnerving part is convincing the people in
               | the black SUVs that you actually haven't been doing
               | anything suspicious. While they tear your house apart.
               | And take all of your stuff. And have you handcuffed on
               | the floor.
        
           | Firerouge wrote:
           | Wild, the police thought that the LED display, that had
           | already been up for 4 weeks, might be a bomb, and then they
           | somehow spent a million dollars handling the 'threat'.
           | 
           | Wilder still, Turner bought off the police after for 2
           | million dollars, and then censored the creators from
           | releasing an episode critical of the Boston police response.
        
             | anon9001 wrote:
             | If you ask yourself where the money comes from, who gets to
             | decides to spend it, and how much fun the police had
             | playing with their toys, it all seems to make good sense.
        
           | OJFord wrote:
           | Main article link made a lot more sense to me, having never
           | heard of it (or ATHF) before:
           | 
           | https://en.wikipedia.org/wiki/2007_Boston_Mooninite_panic
        
       | alhirzel wrote:
       | Reminds me of Mitsuba 2; see Caustic Design at about 3 mins into
       | the first video:
       | http://rgl.epfl.ch/publications/NimierDavidVicini2019Mitsuba...
        
         | _Microft wrote:
         | That's impressive. Here someone created a slab of glass that
         | turns the caustics into a picture of his cat:
         | https://mattferraro.dev/posts/caustics-engineering
         | 
         | (discovered via: https://news.ycombinator.com/item?id=29063617
         | )
        
           | diplodocusaur wrote:
           | 'two minute papers' has a link to a free course on how to do
           | this. I haven't checked them out.
           | https://www.youtube.com/watch?v=_r-eIKkyAco Note: the title
           | says 3d printing but it's actually milling acryllic sheets,
           | not SLA
        
       | jacquesm wrote:
       | What an absolutely amazing piece of work, and even more
       | incredible that it worked the first time. If I had to do
       | something like that it would take me at least three tries to get
       | it to work and quite possibly more than three. Math, 3D printing,
       | love, what's not to like :)
       | 
       | And congratulations!
        
         | djmips wrote:
         | 20 hours into printing the final mirror array frame he realized
         | it was backwards and would have displayed "?EM YRRAM". So he
         | had to scrap that and restart his print. So let's call that a
         | try. ;-)
        
         | codazoda wrote:
         | Even simple stuff takes me multiple tries. I don't know how any
         | engineer gets a design right the first time. I can build it in
         | a 3D design app, look all around it, and STILL see something in
         | the prototype that was not obvious in the design.
        
           | alok-g wrote:
           | I have gotten designs first-time right multiple times in my
           | career, and in fact more often first-time right than not. And
           | so for both hardware and software.
           | 
           | For the last few years however I have gradually been loosing
           | that and have started going easier on myself when I discover
           | a mistake.
           | 
           | The requirement to get it right in the first time is more
           | stringent for integrated circuit designers (which I have been
           | too) as cycle times are in months. It is true that several
           | tools are set up around this to help find issues before
           | designs are sent out for fabrication. However, the tools are
           | not perfect, and considerable insights, eye for detail and
           | perfectionism and are still required to make a design work in
           | the first shot.
        
           | jacquesm wrote:
           | I just built something I _had_ to get right on the first try
           | because messing it up would be more than a little dangerous.
           | Endless fitting and testing and re-thinking before committing
           | to building it. A little cheating was involved, I built a 1
           | /17th scale test setup to ensure that all the electrical bits
           | would work.
        
             | stavros wrote:
             | Does it?!
        
               | jacquesm wrote:
               | Yes, it works. Test rides three days ago, first real trip
               | yesterday, 65 km there and back on a single charge.
               | Write-up one of these days, have to collect all the
               | material.
        
               | stavros wrote:
               | Excellent.
        
               | jacquesm wrote:
               | I've never actually been scared of stuff I built before,
               | that's a first (and that doesn't mean that I shouldn't
               | have been scared with other projects, just that I wasn't
               | either because I wasn't aware they were dangerous or
               | simply too absorbed to stop and think about it).
        
               | tomcam wrote:
               | Wait what did you build?
        
               | jacquesm wrote:
               | It's up:
               | 
               | https://news.ycombinator.com/item?id=29198205
        
               | tomcam wrote:
               | Wow! Congratulations, you beast!
        
               | jacquesm wrote:
               | Very large battery pack for an e-bike. I'll do a write-up
               | soon, still have to collect all the pictures and the
               | text. It works incredibly well but it took way too long
               | to make.
        
               | PostThisTooFast wrote:
               | Rides? Of what? What is this referring to?
               | 
               | Some important information has been omitted from this
               | thread.
        
               | nynx wrote:
               | Electric bike?
        
               | jacquesm wrote:
               | 2KWh+ battery pack in a very weird shape.
        
       | nayuki wrote:
       | Someone else's work that alters light transmission (instead of
       | reflection): https://mattferraro.dev/posts/caustics-engineering
        
       | mlatu wrote:
       | That is so nice, thank you for sharing
        
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