Computational Hydrographic Printing [video] | Hacker News Reader

Computational Hydrographic Printing [video]

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I was amazed until they got to the cat (about 3:00 in). At that point I was blown away. The inside surfaces of the "outside" legs were also accounted for in the mapping, and it was spot on.

This is seriously cool.

Yes, it's pretty seamless on boundaries.

This is incredible but I'm assuming that the print and the objects are painstakingly aligned as the immersion rod has no lateral movement.

Sure seems like something that could be easily remedied in future iterations. They've already figured out the hard part; alignment is a solved problem for all intents and purposes.

Yeah, that was the thing that impressed me most, too.

If anyone is interested in the other papers that are presented at SIGGRAPH 2015, Ke-Sen Huang usually has a complete list with links to preprints and videos. You can find the list for SIGGRAPH 2015 here:

http://kesen.realtimerendering.com/sig2015.html

My favorite paper this year is "The SGGX Microflake Distribution" by E. Heitz et al. Sadly there aren't many papers on rendering this year.

No technical paper preview trailer this year?

I am always jealous of how cool and flashy the work at SIGGRAPH is.

The amazement never fades, every year brings its share of complex maths and aesthetic sensations.

I love how this is a complementary technology to 3D printing by the way of a traditional printer. Simple. Effective. The biggest obstacle for widespread adoption might be software, in other words a robust toolkit for designing "wraps" of these imprints for your own 3D models.

Well I may just be suffering from the curse of knowledge, but I found blenders texture paint system to be very good.

Once set, you can employ so many techniques with it to map images to a 3d model.

Wow, multiple pass dipping was awesome. I wonder if there's some kind of 3d painting machine that can compete with this.

What kind of surface doesn't fit this computational model? The elephant one for example, how to map the region which is occluded by the elephant's nose to the PVA surface? Anyway, really nice work. Looking forward to reading the paper and learn more!

The failure modes listed in the paper are models with a lot of concavities or self-occlusions. Looking at the video, it looks like the elephant cup succeeds because of surface tension properties of the water, which let the surface on each side of the trunk "snap together" when the trunk begins to be completely immersed. It's that wrapping or stretching that lets it be more than a simple light projection, which would fail due to self-occlusion.

Thanks. I found this in the paper too. Like you said, high concavity and significant self-occlusion are two cases that are more likely to fail.

Very cool. Anyone know how a sphere (the globe at the end) was printed in a single immersion? Based on what I saw in the video, it seems like it would have to be a different process involving rotating the sphere as it was dipped, rather than the linear motion used for the other objects.

Was the sphere inside the globe framework when it was printed? If it was merely a sphere being immersed, then perhaps a polar projection map would be able to cover all of it.

From the paper[1], it sounds like the same linear motion with the film wrapping around to the top:

    > The sphere is dipped with
    > its north pole pointing downward. The maximum error on the
    > northern hemisphere is within 2mm. However, near its south pole
    > the error is much larger (about 5mm). This is because after the
    > water surface passes the sphere’s equator, the film gets stretched
    > largely, and near the south pole the relative angle between the
    > water surface and the object surface approaches to 180◦, leading
    > to an ill-posed boundary condition for our simulation (recall
    > Equation (1), when θ ≈ 180◦).

You can see the potential for a similar wraparound even on e.g. the mask dips.

[1] http://www.kunzhou.net/2015/hydrographics.pdf

Don't believe so, a single projection with antarctica on the outside and the north pole at the centre would likely work just fine - and they showed it top-down.

Interesting, This appears to be texture re-projection. The novel bit is accounting for the elasticity of the PVA film.

For those of you who aren't in 3d/VFX:

UV mapping is essentially this process. Most 3d models you'll see, the colour you see started out as a 2d image

http://wiki.blender.org/index.php/Doc:2.4/Manual/Textures/Ma... has a good example of how texture are extracted from a 3d model.

Do you know what those cloverleaf shaped metal beams are called, and how you can learn more about building hardware prototypes with those kinds of products?

I know very little about mechanical engineering and hardware prototyping, but I saw those metal thingies about a year ago in a DYI tinkerer community (it was used in a DYI 3D printer), and I have been wondering about that topic ever since.

Those metal beams are called aluminum extrusions and are sometimes referred to by the brand name "80/20".

They're super fun and useful in prototyping - kind of like an erector set for adults.

Thanks! What other items often go together with these aluminum extrusions? Is there a place or a book to learn about this topic, or is it something that people only learn through experimentation and mimicking?

In addition to the 8020 beams already mentioned, there are also MakerBeam (http://www.makerbeam.eu/) and OpenBeam (http://www.openbeamusa.com/).

Primarily they are used for building structures quickly and easily - a saw and a wrench are the only tools you need. The standardized brackets for each beam type allow you to make 90 and 45 degree angles.

But they are often used for more than just framing. The 3D printing community has embraced extrusions because you can also use them as bearing surfaces, mount motors and servos, limit switches, etc. Basically anything that has a hole big enough for a machine screw can be mounted to a beam either directly or through an easily made mount (usually to get the angle that you want - all it takes is some sheet metal).

The quickest way to learn is to look at examples. The OpenBeam website has lots of examples. The system is so simple that you can understand exactly what is going on just by seeing a picture.

Wow, this is very cool. They invented a new method for printing taking advantage of the fluid nature of liquid to get to every surface of a 3-D object.

FYI hydrographic printing isn't new... nor is the computational part to be honest. I assume both of these techniques have been used together before, but what we are seeing here is both: very well done, and: using off-the-shelf components.

Bonus the-future-is-now moment: "3D vision systems" are "off-the-shelf components".

What do you mean the computational part isn't new, who has done it before?

I would guess the part that would be commonly done is the texture mapping and the print out of some kind of simple projection

It looks like they have added, crucially, the math to account for the topology of the dipping process.

>>the math to account for the topology

Looks brute force to me as it is base only on the forward problem.

Take for example this technique: https://youtu.be/ljMePAmmxx4

Around 2:10 he mentions "you can actually set it for project as well" which is a lot closer to what's being done in this case.

Blender has to solve nearly the exact same problem for projections, the only differences being the projection has to be mapped backwards to a flat texture, and you have to account for the way the film clings to the surface and how it stretches. Topology and topography aren't an issue though, we've got that so covered. (But the material physics is something you would have to construct a model for, so if you wanted to solve this precise problem in Blender you might have better results with the physics engine.)

I have seen some variation on this available in even low-end 3D modelers since the 90s. IIRC Truespace's version of the feature did shrink-wrapping by running a simulation, much like they do here, but with different physics.

I thought I had even seen this used in printing before but I could be mistaken.

SIGGRAPH season already?

Nope, Chuck Testa

making fake stuff become easier. now we only need to attach the printer to a water tank.

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