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3D printed mirror array (github.com/bencbartlett)
1056 points by agmm 10 months ago | hide | past | favorite | 143 comments

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

"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"

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.

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?

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.

> but Pollock and Mondrian precisely brought the consideration of the process to a new light, that's part of what makes them significant figures.

Oh. I thought people saw something I couldnt.

Linguistically, the art is the process, and the result is a “work of art”. One of my favourite misunderstood language quirks.

> to achieve things could be presented in other ways with minimal effort

You could imagine the art piece with minimal effort: no effort spent in making it. So in a way that's the purest form of art by your criticism. If only there was some way to achieve this, we'd be done.

This is quite close too : https://prusalab.cz/projekty/reflexe/

(Petr Vacek & Adam Cigler / Prusalab / Czech Republic)

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. :)

I also had the chance to see it, and I agree with you : impressive. Glad to know it is still evolving.

That's fascinating - the artist does everything himself from fabrication to design. Looks incredible.

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.

Thank you for linking this.

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

Who is on the Cover of WIRED 1999? Can someone please find out.

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!

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. ;-)

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.

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.

Does it?!

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.

Electric bike?

2KWh+ battery pack in a very weird shape.


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).

Wait what did you build?

Wow! Congratulations, you beast!

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.

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.

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 :-)

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.

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.

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.

What have you been up to that would lead to such an unnerving response? ;-)

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.

Main article link made a lot more sense to me, having never heard of it (or ATHF) before:


> 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)

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.

Was it actually illegal or did they just bully him into doing what they wanted?

like the idea but how much sun does london really get?

Enough to allow a skyscraper to melt cars[0].

[0]: https://www.bbc.com/news/uk-england-london-23930675

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!

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

It sounds like a Danny Rozin piece


Edit; I'm sure it could be https://www.smoothware.com/danny/mirrorsmirror.html

These are close but it was definitely horizontal these are vertical. Thank you for the links!!

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.

Bears a striking resemblance to the James Webb Space Telescope


Reminds me of Mitsuba 2; see Caustic Design at about 3 mins into the first video: http://rgl.epfl.ch/publications/NimierDavidVicini2019Mitsuba...

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 )

'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

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.

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.

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".

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!

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.

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 0.12¢ (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.

I've silvered a lot of copper plates for photography (Daguerrotypes).

Well, as usual, you probably know more than I do about what I'm writing about. Am I overlooking something significant? I don't even know if you can use the Tollens test to silver copper.

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.

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.

Isn't the mirror surface effectively at the aperture in this system...

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.

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.

That's why I'm mentioning the filler. It definitely can't be "very thin". But all that matters is if the resulting shape is predictable.

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.

This is so adorable

Seriously, can it get much better than this?

It should be possible to do animation driven by the movement of the sun in the sky.

Similar to a digital sundial https://en.wikipedia.org/wiki/Digital_sundial

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?

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.

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...

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

Swiss made precision optical gear. I think the price of that little mirror just might make your head spin.

Depends on the desired scale - https://www.youtube.com/watch?v=9nb8mM3uEIc

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.

You could use holography/beamforming to steer a beam from a DLP, although it would be just a small % of the original power.

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.

Absolutely. And it'll keep working on a sandy beach far from any power source.

You'd probably want to use galvos instead of servos for this application (high speed/precision, low load mass).

Or piezo.

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.

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.

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.

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.

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.

Awesome! It's like a giant static DLP chip!

You are correct! This is essentially how office projectors work https://youtu.be/KpatWNi0__o?t=102

The wedding is going to be over the top

Well, it definitely looks like it will be pretty gay! :)

Archimedes would be proud! And you should be too!

Congrats, and thank you so much for sharing this, it totally made my day.

Someone else's work that alters light transmission (instead of reflection): https://mattferraro.dev/posts/caustics-engineering

This idea looks like something you could commercialize!

Now how could we achieve the same thing with just origami? https://jwst.nasa.gov/content/features/origami.html

This project is soooo amazing! Congrats! Great piece of art and engineering

Did you try sinking any ships with this? https://en.wikipedia.org/wiki/Burning_glass

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 ?

Fantastic! I love the creativity that went into this.

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!

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?

You'd need the mirror planes to be adjustable in the XY tilt directions. Seems doable though, would be a cool next project

Or not? That’s an interesting challenge. Multiple messages depending on the light angle

Sort of the opposite of a digital sundial:


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.

I'm wondering how feasible it would be to repurpose this code for a concentrated solar power setup.

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 :).

It’s like the Uber of renting other peoples roofs! (I’ve been watching way too much shark tank the past 3 days…)

This reminds me of company called Leva.

Check out this project https://www.leva.io/projects/kinetic-wall

> 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!

That's mad creative, like those solar clock things

Cool af! Congrats

This idea will have many unexpected applications. For example difficult to remove signs projected to flat surfaces.

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.

You can do that just with a mirror in the shape of an arrow. Or a mirror with a negative arrow painted on it :)

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.

I would love an array of them in the style of old airport signages could be an amazing effect. Great work.

Such a cool idea. Now you have a momento to remember the day that can be hung on a wall.

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.

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!

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.

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.

> virtual reality is delightfully egalitarian

It could be, but I'm willing to bet it'll be primarily used to oppress and control people. The potential for things like VR and AR is great, but the reality is that it will be used against you in ways that couldn't have been possible without it.

Wow how wonderfully geeky romantic. Did he say yes ? [Edit the sand said yes!]

What happens if you point all the mirrors at the same spot? Fire?

Archimedes famously used mirrors to burn a fleet invading Syracuse: https://en.wikipedia.org/wiki/Burning_glass

Nice. Now step 2: individually articulated mirrors :)

This made my day! Nothing technical to say sorry!

That is so nice, thank you for sharing

Absolutely mesmerizing work!

This rocks, and congrats!

Did he say yes?

Congrats! Wonderful!

hats off

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