I install the lab file into addons/labs/labs/math and otherwise would not know how to run the file as a lab without probably a lengthy investigation.

 JVERSION

Engine: j806/j64avx/linux

Beta-3: commercial/2017-04-10T17:51:14

Library: 8.06.09

Qt IDE: 1.6.1/5.3.2

Platform: Linux 64

Installer: J806 install

InstallPath: /home/lambertdw/downloads/installs/j64-806

Contact: www.jsoftware.com

Using jqt I am unable to duplicate

However, when I browse to the .ijt file as a lab, I get:

ctrl+j advances
first open a lab
first open a lab

(and ctrl+j gives me another "first open a lab" line)

-------------------------

Right handed rotation means to point your right hand in the direction of the vector then close your fingers. The rotation is supposed to be in the direction your fingers curve.

I've adjusted notes and examples in my private copy. Thank you!

I wrote the original version of this code more than 15 years ago in python to help learn Tkinter. And made a keyboard controlled rotating Buckyball. Were I to implement the projection from homogenious coordinates to 2 dimensions we'd need to know that the conversion to 3D works by division by H, thus scaling 1 1 1 1r2 is the same as scaling 2 2 2, so the issue that I've chosen scaling to include 4 {.!.1 may be confusing. The projection onto screen coordinates, which are left handed, involves congruent triangles which just might be too difficult for my ancient head. For moving meshes into place I assume H=1.

On 03/13/2018 08:00 AM, programming-requ...@forums.jsoftware.com wrote:
Date: Mon, 12 Mar 2018 13:58:31 -0400
From: Raul Miller<rauldmil...@gmail.com>
To: Programming forum<programm...@jsoftware.com>
Subject: Re: [Jprogramming] Homogeneous coordinates module and lab
        proposal
Message-ID:
        <CAD2jOU9a337Z1FUU=D1ygAFOD2BLwjSJo2NHrFxV6b=qe0p...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

That (thinking that I was dealing with one file when I was dealing
with two) was the mistake I made, thanks.

I can now load the .ijs file.

However, when I browse to the .ijt file as a lab, I get:

ctrl+j advances
first open a lab
first open a lab

(and ctrl+j gives me another "first open a lab" line)

So that might need a little work?

Thanks,

-- Raul
------------------------------

Message: 3
Date: Mon, 12 Mar 2018 15:59:10 -0400
From: Brian Schott<schott.br...@gmail.com>
To: Programming forum<programm...@jsoftware.com>
Subject: Re: [Jprogramming] Homogeneous coordinates module and lab
        proposal
Message-ID:
        <caedwnsumz9+59-ayekdnorwb5kk55+isurrxmcm1rsdywe1...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

David,

I have not tested your code.
I have gotten bogged down in the detail, but am very impressed with the
idea of creating such a lib and lab. It is especially clever that you are
using your new method of creating verbs with built in Descriptions. If you
have not already done so, I would mention that tie in, in the wiki page and
the lab.

One thing I did not like was your definition of scaling because the
description example using 1 3 does not generalize well. I think the right
hand argument of 1 3 1 1 would be better, in its generalizability.

scaling=: (I4 * 4 {.!.1 ]) Description'scaling 1 3 yields a scaling matrix
intended to scale the second coordinate by 3'

I noticed you mention "the right handed rotation matrix about a vector".
Without my duplicating your calculations, I am not clear what is
right-handed. For example the the transformation matrix meant to be on the
right side in the multiplication with the vectors? is the axis system
right-handed? Could you also clear up whether your system applies to both
left- and right-handed axes systems, or not?

If you have not seen Eric's rotating cube in JHS, you might find it
insightful. I was reminded of the JHS demo while searching rosettacode.org
where I found that J has not contributed to the task at
http://rosettacode.org/wiki/Draw_a_rotating_cube. I'm not able to
investigate jdemo12.ijs could be easily adapted to the rosettacode task.

j64-806/addons/ide/jhs/demo/jdemo12.ijs

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