@topher_batty@mastodon.acm.org avatar

topher_batty

@topher_batty@mastodon.acm.org

Associate Professor in CS at University of Waterloo doing computer graphics and computational physics. I also manage https://physicsbasedanimation.com and maintain a list of graphics researchers on Mastodon: https://christopherbatty.github.io/Mastodon-Graphics-Academics/

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topher_batty, to random
@topher_batty@mastodon.acm.org avatar

The first of the two SIGGRAPH North America 2024 papers I'm on is "Reach for the Arcs: Reconstructing Surfaces
from SDFs via Tangent Points" https://odedstein.com/projects/reach-for-the-arcs/

Building on our SIG Asia "Reach for the Spheres" idea, we interpret discrete signed distance field data as a collection of spheres, to which the unknown surface must lie tangent at (at least) one point. We further observe that only the "arcs" of spheres not covered by other spheres can host valid closest/tangent points.

j_bertolotti, to random
@j_bertolotti@mathstodon.xyz avatar

People studying brains: "We found no correlation between number of neurons and IQ."*

People talking about AI: "If we just add more nodes to our deep neural network we are surely going to create a super-mind!"

topher_batty,
@topher_batty@mastodon.acm.org avatar

@j_bertolotti for this to be evidence of something, doesn't it assume that NNs are equivalent to physical neurons? Is that really true?

nervous_jesse, to random
@nervous_jesse@mathstodon.xyz avatar

There's a lot of obfuscation in scientific papers, especially when it comes to mathematification. A good one is when there is an algorithm with a magic number in it, so they just call it a "variable," and then they're like in all our examples we set this variable to SOME_VALUE. This is because arbitrary numbers are considered bad practice, but if it's a variable we've tuned then it was a scientific process.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@nervous_jesse I mean, probably better to acknowledge it's an empirically chosen parameter value that seems to work, than to claim it's the one true perfect magic number that shall not be questioned. But yeah, it's still magic numbers at the end of the day.

aeva, to random
@aeva@mastodon.gamedev.place avatar

random brain wandering:

Suppose you have a cellular space like a grid or a quad tree or such. Each cell intersecting a shape (say, a triangle) records relative surface feature (say, a plane) that might be useful for recovering or extrapolating a nearest point on surface. Maybe a cell stores an authoritative surface feature, or maybe it can have several, doesn't really matter for this post.

Then, empty neighbors use that data to generate their own (non-overlapping) relative surface features.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@demofox @aeva also more or less describes the mesh to SDF construction algorithm in my Github (shamelessly stolen from my PhD supervisor, I just added the cmdline interface)

demofox, to random
@demofox@mastodon.gamedev.place avatar

Somedays it's a lot easier than others to understand why Lao Tse wandered off into the wilderness 😂

topher_batty,
@topher_batty@mastodon.acm.org avatar

@aeva @demofox I don't know, if 'agile scrum' can weasel its way even into polycules, the wilderness itself can't be far behind... https://www.nytimes.com/interactive/2024/04/15/magazine/polycule-polyamory-boston.html

HeavenlyPossum, to random
@HeavenlyPossum@kolektiva.social avatar

“How would we do this or that under anarchism?”

Consensually, through voluntary agreement, or by yourself, without coercive interference.

I’m sure that sounds like a cop-out to a lot of people, but it’s based on a principle of humility: we can’t possibly know what solutions people will pursue, negotiate, and adapt to the ever-evolving problems we face in the world.

Some anarchists have invested a lot of work in figuring out how we might organize ourselves if free—federations of councils and the like—and that work is valuable. Some people might adopt some of those solutions some of the time. But it’s not for me or anyone else to prejudge or insist upon any particular solution.

We’ll do it together, in free cooperation, by talking to each other, persuading each other, inducing each other, or by leaving each other alone.

1/

topher_batty,
@topher_batty@mastodon.acm.org avatar

@HeavenlyPossum I have no background in any of this, so excuse my dumb questions: isn't there a prisoner's dilemma-like element here? Aren't you at the mercy of any single person (or group) who decides they hate all your bothersome negotiating and simply takes up arms to force their will? If they decide they're the state now, aren't you (and your society) powerless, since you cannot coerce/force them to stop? It all seems to collapse upon contact with any disagreeable person(s).

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

Check out my latest collaboration with Tetsuya Takahashi on efficiently solving box-constrained QPs, especially for fluid animation problems on Cartesian grids, using an interior point method and a tailored algebraic multigrid preconditioner: https://tetsuya-takahashi.github.io/PD_BCQP/
And here's the YouTube link:
https://www.youtube.com/watch?v=GeeweiNzcOQ

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

So far this year a quick Google turns up only two SIGGRAPH 2024 authors that have prematurely broken anonymity on their websites before receiving final acceptance of their paper. That's not half bad given the number of papers accepted.

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

Fun typo in this quote from a Hollywood Reporter story about Netflix's 3 Body Problem: “Liu Cixin’s created this inedible trilogy and the books just get better for me." Completely changes the metaphor, and meaning. https://www.hollywoodreporter.com/tv/tv-features/3-body-problem-season-2-netflix-1235857474/

HeavenlyPossum, to random
@HeavenlyPossum@kolektiva.social avatar

If Biden loses—or, more likely, if Trump coups his way into power—I fully expect that a lot of liberals will devote more of their energy into yelling at people online for not voting hard enough than in resisting the fascism they keep warning us is imminent.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@HeavenlyPossum leftist preemptively ineffectually scolding liberals for hypothetically ineffectually scolding leftists? A few more rounds of this back and forth and we'll surely have the whole thing solved! 😀

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

Our paper on solving Poisson problems using Monte Carlo raytracing-like techniques now has a video up on youtube, thanks to first author Ryusuke Sugimoto: https://www.youtube.com/watch?v=5SDhXJ3Sjmo

jaztrophysicist, to creative
@jaztrophysicist@astrodon.social avatar

A truly non-Newtonian black hole #Creative #Physics #Astrodon #Science #Photography #Bass

Close-up video of honey dripping from a wooden spoon. The spoon is set against the light so that the background appears dark. Light gets through the honey drips and drops, making some lenses effects. Some sparky bubbles made by chromatic refraction are visible inside the drips. The drips make oscillatory movements due to the non-newtonian (elastic) nature of the fluid. The whole scene looks like a black hole image, with the dark centre (the spoon) surrounded by a light ring (the honey bending the light by refraction)

topher_batty,
@topher_batty@mastodon.acm.org avatar

@nholzschuch @antoinechambertloir @jaztrophysicist my French isn't great, but yeah, the 'normal' way people would simulate something like this would be solving Navier-Stokes throughout the liquid volume, using a geometric surface representation that can deform and change topology )like particles or a mesh or signed distance field). The physics would be, as you said, Navier-Stokes (pressure, viscosity, advection) with surface tension on the surface.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@nholzschuch @antoinechambertloir @jaztrophysicist if the liquid really is non-Newtonian (e.g., nonlinear viscosity coefficient, elastic forces, etc.), then those additional forces would also be incorporated into the Navier-Stokes solver.

aeva, to random
@aeva@mastodon.gamedev.place avatar

I've worked up quite a hunger by staying in bed all day and thinking too hard about geometry 😌

topher_batty,
@topher_batty@mastodon.acm.org avatar

@aeva i think sphere trees are a classical bounding hierarchy approach, see e.g. http://graphics.cs.cmu.edu/projects/bdtree/jamespai_bdtree04.pdf and references therein.

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

I occasionally think fondly of this old Square One song about Tesselations.
https://www.youtube.com/watch?v=sFwSpw7Bv3s

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

Actually pretty excited to attend my first ever SIGGRAPH Asia next week! Only took me 15 years to get around to it.

I'll be chairing the Fluid Simulation session on Tuesday and @silviasellan is presenting our paper on SDF reconstruction at the Reconstruction session on Thursday. See ya there.

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

I like when academics say "I'm looking for a postdoc" because you don't know if they want to be one, want to hire one, or just misplaced one somewhere.

jbigham, to random
@jbigham@hci.social avatar

politics is a lot more interesting than we give it credit for … kudos to Governor Beshear, and kudos to the buckeyes

https://www.nytimes.com/live/2023/11/07/us/election-day-2023

topher_batty,
@topher_batty@mastodon.acm.org avatar

@jbigham well, now we won't have to worry about Joe Manchin anymore.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@jbigham as far as Senate votes anyway!

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

The code for our "Reach for the Spheres" SDF reconstruction paper is now online: https://github.com/sgsellan/reach-for-the-spheres/

topher_batty, to random
@topher_batty@mastodon.acm.org avatar

For computer graphics academics and researchers, I threw this list of folks together. Apologies if I've forgotten anyone or included anyone who prefers to be forgotten! Let me know if there are any errors or corrections. Hoping this will help folks migrating from the birdsite. 🙂
https://christopherbatty.github.io/Mastodon-Graphics-Academics/

topher_batty,
@topher_batty@mastodon.acm.org avatar

@aeva Thanks! I put it together mostly by hand because whatever version of mastodon my server is on doesn't seem to exports lists. Ah well.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@aeva I have fixed a couple more trailing @'s and other silly things. Thanks again!

scheidegger, to random
@scheidegger@mastodon.social avatar

I was expecting stupid, and this is worse. It's stupid and anodyne. Fuck this guy.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@scheidegger @jennybryan literal LOL. I stopped reading long before that point I guess.

topher_batty,
@topher_batty@mastodon.acm.org avatar

@scheidegger @jennybryan no doubt. But yeah, that's the guy that founded Guelph.

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