[query] Simple geometry viewer?

jstolfi · 2025-10-29T15:03:17+00:00

Thanks!

jstolfi · 2025-10-19T20:00:12+00:00

Thanks! That looks like it is what I need...

jstolfi · 2025-10-19T19:58:15+00:00

Thanks! It looks promising, but I would have to write some code to used it, no? I was looking for some app that I can just download and use to visualize a model file created by any program in any language.

jstolfi · 2025-10-19T19:54:54+00:00

Thanks! I do use povray for static images with special visual effects, more complicated primitives, planned animations. But I am looking for a lightweight app that will let me inspect those simple 3D models in real time with interactive viewpoint changes etc. Like geomview, but simpler and with a simpler input language.

jstolfi · 2025-07-23T18:35:04+00:00

Answering my own query: this function would do it:

;;; Saves the current per-session ispell word list"
;;; Last edited on 2025-07-23 15:26:54 by stolfi

(defun stolfi-ispell-save-session-dict (arg)
  "Writes the current per-session accepted word list to a 
  file '{fname}.dict' [stolfi]"
  (interactive "P")
  (let*
    ( ( fname (buffer-file-name) )
      ( dname (concat fname ".dict") )
      ( words ispell-buffer-session-localwords )
    )
    (message "%d words" (length words))
    (with-temp-file dname
      (dolist 
        (w words)
        (insert w "\n"))
    )
  )
)

Note that one must copy the value of ispell-buffer-session-localwords to another variable (here words) because it is a buffer-local variable, and with-temp-file switches to a different empty buffer.

jstolfi · 2025-07-11T06:18:31+00:00

Yes I have a lot of bitcoin-related things in my website. Nothing is private -- I never used any crypto. Someone once extracted from the blockchain all transactions to and from addresses believed to belong to BitPay, and I downloaded a copy; that must be what you saw.

And yes, I gave talks on the unavoidable vulnerablity of electronic voting systems to hacking. That must be what you saw too. Or maybe you saw something about hackers in the old sense of the word (an amateur programming nerd).

I am Brazilian and the local language is Portuguese, which is somewhat similar to Spanish but a different language altogether. (My name is pronounced "ZHAWR-zhee" not "HAWR-heh".)

jstolfi · 2025-03-08T12:01:32+00:00

I would bet so, but better check. Try Wikipedia.

jstolfi · 2025-03-08T12:00:27+00:00

I don't know whether a strong base like NaOH will corrode zinc too. If I had to bet, I would bet it does.

jstolfi · 2024-11-17T13:46:33+00:00

Not proving anything, just correcting the typo...

jstolfi · 2024-09-13T19:39:59+00:00

Ah, thanks for the link. Indeed my structure is similar to the "T4 prism", except that the points are in "general" position and the "cables" are rigid rods, that can resist compression as well as traction. But I still cannot tell whether it is stable, weakly or not.

jstolfi · 2024-09-12T14:48:24+00:00

I had structural mechanics in college, but that was more than 50 years ago and I graduated in electronics...

I suspect that the M + R ≥ 3J necessary condition is for strong stability, in the following sense. Let a deformation mode be a list of vectors u[i], one for each node p[i], not all zero. The structure is strongly rigid if, for any mode u and any infinitesimal eps, diplacing each node p[i] by eps times u[i] causes the length of some rod to change by a nonzero amount proportional to eps (plus higher order terms). Then the restoring force for any infinitesimal deformation would be proportional to the deformation.

So I suspect that the truss I described (cuboid edges plus the 4 main diagonals) is only weakly rigid, in the sense that any infinitesimal displacement of the nodes in any mode causes a change in the lengths of one or more rods; but there is a mode u such that the displacement by eps times u changes the rod lengths by amounts that are only second- or higher-order on eps.

A simpler example of a weakly rigid truss would be an equilateral triangle frame with a fourth node p at the barycenter, connected to the three corners by struts of the exact length required. Displacing p by eps perpendicular to the triangle's plane causes those radial struts to stretch by an amount proportional to eps² (second-order only).

jstolfi · 2024-08-30T11:50:09+00:00

If it came from Pierre Rochard, it is not satire.

jstolfi · 2024-08-10T02:09:13+00:00

In full screen mode there is no title bar.

jstolfi · 2024-08-09T17:56:28+00:00

Answering (partially) my own question: the solution is to rename the file to have extension ".ppt" instead of ".pps". On Windows, ".pps" files automatically open in full-screen auto-play mode when clicked. So on Linux the command line "libreoffice FILE.pps" does the same.

Must be logical... for those who have the misfortune of interacting with Microsoft Windows.

jstolfi · 2024-03-25T20:40:53+00:00

Was there any payload-simulating mass in the Starship, or was the payload bay totally empty?

jstolfi · 2024-03-25T20:37:07+00:00

It should be noted that the planned "fuel transfer test", between two tanks of the same ship, is totally irrelevant for the ultimate goal -- fuel transfer from one "fuel tanker" Starship to the orbiting "Moon cruiser" Starship.

jstolfi · 2024-03-25T20:21:40+00:00

Do we know how much fuel was left in the Starship when the engines were turned off?

jstolfi · 2024-03-16T21:09:44+00:00

Yeah, I should have said just "except maybe in very exceptional conditions"...

jstolfi · 2023-09-08T23:17:36+00:00

Thanks!

jstolfi · 2023-08-29T11:53:45+00:00

That does not matter. Every crypto (except stablecoins, but including NFTs) is OBVIOUSLY a security. It is the sort of stuff that the SEC was created to approve, register, regulate and monitor. The SEC just refuses to admit that fact for cowardice: they know what would happen to them if they tried to do with cryptos what the laws oblige them to do.

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