Re: Quaternions (was Re: Default signedness of 'plain' char.)

From	"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Quaternions (was Re: Default signedness of 'plain' char.)
Date	2026-08-12 12:52 -0700
Organization	A noiseless patient Spider
Message-ID	<115iiuo$13bf2$1@dont-email.me> (permalink)
References	(17 earlier) <115feen$3msd$1@dont-email.me> <115fuu3$93db$1@dont-email.me> <115gpod$gl9f$1@dont-email.me> <115h3s1$jc1e$1@dont-email.me> <115h8e4$k5gh$2@dont-email.me>

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On 8/12/2026 12:47 AM, Lawrence D’Oliveiro wrote:
> On Wed, 12 Aug 2026 01:24:32 -0500, BGB wrote:
> 
>> Say, if lerping between two points that are nearly 360 degrees
>> apart, then, the interpolation will tend to perform an unexpected
>> full-rotation.
> 
> Been there, done that, with actual 3D modelling/animation software
> (Blender).
> 
> Takes some careful placement of extra keyframes to get the rotation to
> come out right ;).
> 
>> I have found I would rather not use point-and-click tools for 3D
>> modeling (weird, I know).
> 
> CG is very much a mix of art and science. You can’t be very effective
> if you are only good on one side.
> 
> Blender includes a feature called “Geometry Nodes”, sort of a
> graphical programming language for geometry-generation/manipulation.

Geometry Nodes in blender are okay, especially with instances. For 
instance one of my script dumps out points. Each point has a scale and a 
rotation. The nodes tap into that. Here is an example result:

https://skfb.ly/pzTEC

However, the script lang is slow, its kind of a "hog", the blender. 
Using C or C++ for generating the geometry is a lot faster. no big ass 
pig IDE to slog around in. But, Blender is pretty nice. But. Its a bit 
fat...

> Do you remember Alan Turing’s paper on reaction/diffusion systems,
> where he came up with a mathematical theory on how a symmetrical clump
> of cells making up a fertilized embryo can decide which is head, which
> is tail, which is left and which is right? Here
> <https://www.youtube.com/watch?v=RSpkkuOOtBw> is a tutorial on how to
> implement such a system to produce some crazy patterns.

I have a way for DLA to not use any random numbers. Don't really want to 
publish my technique yet, but here is an example:

NO random numbers were used:

https://youtu.be/mqYBMuvVJI8

Thread

Default signedness of 'plain' char. gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-02 14:17 +0000
  Re: Default signedness of 'plain' char. Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-03 02:45 +0800
    Re: Default signedness of 'plain' char. gazelle@shell.xmission.com (Kenny McCormack) - 2026-08-03 01:47 +0000
      Re: Default signedness of 'plain' char. Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-03 23:14 +0800
        Re: Default signedness of 'plain' char. bart <bc@freeuk.com> - 2026-08-03 17:04 +0100
          The Spanish Inquisition (was: Re: Default signedness of 'plain' char.) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-04 00:23 +0800
            Re: The Spanish Inquisition bart <bc@freeuk.com> - 2026-08-03 18:03 +0100
              Re: The Spanish Inquisition Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-04 01:26 +0800
        Re: Default signedness of 'plain' char. Theo <theom+news@chiark.greenend.org.uk> - 2026-08-04 13:13 +0100
          Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 07:30 +0000
            Re: Default signedness of 'plain' char. Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-05 18:18 +0800
              Re: Default signedness of 'plain' char. bart <bc@freeuk.com> - 2026-08-05 17:20 +0100
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 21:57 +0000
                Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-05 15:29 -0700
  Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-03 09:56 +0200
    Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-03 13:56 -0500
  Re: Default signedness of 'plain' char. antispam@fricas.org (Waldek Hebisch) - 2026-08-03 13:48 +0000
  Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-03 14:47 +0000
  Re: Default signedness of 'plain' char. Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-08-03 14:47 +0000
    Re: Default signedness of 'plain' char. Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-08-03 15:04 +0000
      Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-03 16:58 -0700
        Re: Default signedness of 'plain' char. Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-08-04 15:10 +0000
          Re: Default signedness of 'plain' char. scott@slp53.sl.home (Scott Lurndal) - 2026-08-04 15:50 +0000
          Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 03:00 +0000
          Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-05 09:01 +0200
      Re: Default signedness of 'plain' char. antispam@fricas.org (Waldek Hebisch) - 2026-08-04 18:10 +0000
        Compilers targetting the C64 (was: Re: Default signedness of 'plain' char.) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-05 03:17 +0800
        Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-04 16:25 -0500
        Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 02:57 +0000
          Re: Default signedness of 'plain' char. Lynn McGuire <lynnmcguire5@gmail.com> - 2026-08-05 00:19 -0500
            Re: Default signedness of 'plain' char. Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-05 18:57 +0800
            Re: Default signedness of 'plain' char. scott@slp53.sl.home (Scott Lurndal) - 2026-08-05 14:33 +0000
            Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-05 22:38 +0000
        Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-04 21:36 -0700
          Re: Default signedness of 'plain' char. antispam@fricas.org (Waldek Hebisch) - 2026-08-06 00:21 +0000
  Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-03 13:20 -0700
    Re: Default signedness of 'plain' char. bart <bc@freeuk.com> - 2026-08-03 22:06 +0100
      Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-03 14:25 -0700
        Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-03 18:38 -0500
          Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-03 19:34 -0700
            Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-05 04:40 -0500
          Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 07:22 +0000
            Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-05 04:02 -0500
              Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-05 12:35 +0200
              Re: Default signedness of 'plain' char. Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-05 18:49 +0800
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-05 12:39 -0700
                Dear Chris (was: Re: Default signedness of 'plain' char.) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-06 20:15 +0800
                Re: Dear Chris bart <bc@freeuk.com> - 2026-08-06 15:05 +0100
                Re: Dear Chris Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-08-06 23:16 +0800
                Re: Dear Chris David Brown <david.brown@hesbynett.no> - 2026-08-06 20:10 +0200
              Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 21:54 +0000
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-06 04:49 -0500
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-07 00:10 +0000
                Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-07 09:56 +0200
            Re: Default signedness of 'plain' char. James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-08-05 13:33 -0400
              Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 21:50 +0000
                Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-06 10:34 +0200
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-09 15:19 -0500
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-09 20:33 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-09 18:04 -0700
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-10 02:45 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-10 02:24 -0700
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-09 18:03 -0700
                Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-10 08:58 +0200
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-10 15:17 -0500
                Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-10 15:19 -0700
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-10 17:31 -0500
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-10 23:48 +0000
                Re: Default signedness of 'plain' char. James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-08-10 20:03 -0400
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-10 20:44 -0500
                Re: Default signedness of 'plain' char. James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-08-11 11:17 -0400
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-11 14:54 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-12 03:36 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) BGB <cr88192@gmail.com> - 2026-08-12 01:24 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-12 07:47 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-12 12:52 -0700
                Re: Quaternions (was Re: Default signedness of 'plain' char.) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-12 12:56 -0700
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-13 02:16 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-12 21:04 -0700
                Re: Quaternions (was Re: Default signedness of 'plain' char.) BGB <cr88192@gmail.com> - 2026-08-12 23:07 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-13 05:00 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) BGB <cr88192@gmail.com> - 2026-08-13 04:37 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-13 14:36 -0700
                Re: Quaternions (was Re: Default signedness of 'plain' char.) BGB <cr88192@gmail.com> - 2026-08-13 23:07 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-13 23:44 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-13 18:50 -0700
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-14 02:41 +0000
                Re: Quaternions (was Re: Default signedness of 'plain' char.) BGB <cr88192@gmail.com> - 2026-08-13 23:47 -0500
                Re: Quaternions (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-14 04:59 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-11 13:47 -0700
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-13 23:50 -0500
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-14 05:59 +0000
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-14 03:16 -0500
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-14 08:32 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-14 12:36 -0700
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-15 03:16 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-14 22:38 -0700
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-16 00:08 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-14 12:17 -0700
                Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-11 13:46 +0000
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-11 13:49 -0700
                Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-11 08:58 +0200
                Re: Default signedness of 'plain' char. BGB <cr88192@gmail.com> - 2026-08-11 04:03 -0500
                Re: Default signedness of 'plain' char. steve g <Sgonedes1977@gmail.com> - 2026-08-10 20:29 -0400
                Re: Vectors! Quaternions! (was Re: Default signedness of 'plain' char.) Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-11 03:58 +0000
                Re: Default signedness of 'plain' char. David Brown <david.brown@hesbynett.no> - 2026-08-11 09:06 +0200
                Re: Default signedness of 'plain' char. Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-08-10 21:15 -0700
                Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-11 04:52 +0000
                Re: Default signedness of 'plain' char. Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-08-11 06:45 -0700
                Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-11 14:01 -0700
            Re: Default signedness of 'plain' char. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-08-05 12:36 -0700
    Re: Default signedness of 'plain' char. Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-08-05 07:18 +0000
  Re: Default signedness of 'plain' char. Lynn McGuire <lynnmcguire5@gmail.com> - 2026-08-05 18:30 -0500
    Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-05 16:41 -0700
      Re: Default signedness of 'plain' char. bart <bc@freeuk.com> - 2026-08-06 01:24 +0100
        Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-05 17:46 -0700
        Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-06 22:59 +0000
          Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-06 19:54 -0700
            Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-07 11:02 +0000
              Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-07 10:35 -0700
                Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-07 18:32 +0000
                Re: Default signedness of 'plain' char. Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-08-07 20:55 +0200
              Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-08-07 20:51 +0200
                Re: Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-07 13:03 -0700
                Re: Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-07 13:32 -0700
                Re: Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-07 21:44 +0000
                Re: Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-08-07 23:47 +0200
                Re: Use of isascii() back in early days (was Re: Default signedness of 'plain' char.) Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-07 15:26 -0700
      Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-06 22:57 +0000
        Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-06 18:23 -0700
          Re: Default signedness of 'plain' char. cross@spitfire.i.gajendra.net (Dan Cross) - 2026-08-07 11:47 +0000
    Re: Default signedness of 'plain' char. scott@slp53.sl.home (Scott Lurndal) - 2026-08-06 14:40 +0000
      Re: Default signedness of 'plain' char. Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-08-06 15:33 -0700

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