Coordinate systems - comments from Carl

From: "Carl Vilbrandt"
To: Martin Baker
Subject: I would like to work on the project with you.
Date: 26 June 2002 01:49

Dear Martin,

I posted the message and I am sending you this e-mail as a backup.

I would like to collaborate with you in your work, because I am doing
the same work. The think the idea of experiencing 3D space to
understand the theory is great and you have done some great work. I
have spent a great deal of my life 20 years + of modeling in 3D space
teaching and applying modeling and simulations. I know you are going to
not agree with me and most likely be angry at me not believe me ect....,
but you have made a very big mistake, that is more important to the
application of 3D space and computer simulation than you know. Z is up
in engineering, and aviation. Yes in theory any of the axis could be up
and in theory this is not a problem. Looking a a 2D vertical screen the
Y orientation appears to be up, but that is not the proper way to read
the vertical screen. The view presented on a vertical screen is
rotated 90 degrees from the flat horizontal table top that held a piece
of paper instead of a screen. The X,Y plane is a top view looking
down from the positive vertical Z direction and you are looking down on
a plan view which is the first plane established by X and Y. If you
present a 3/4 view on the screen or paper of the X, Y and Z axes the Z
axes is up. It seems that current vertical working position mostly in
2D by programers at first, that has been made possible by digital
processes has given many digital people the orientation of Y as up.
Even the basic Open GL lib's.. if used as they are without appropriate
transformations will result in not only Y up but the left hand rule.
Check out the orientation of AutoCAD or Pro Engineer and you will find
they use the right hand rule with Z up. Many other animation packages
and rendering systems use not only Y up, but the left hand rule........
My favorite is Pov Ray.... :-))) Yup! they are all wrong.
The logical order of creation in the natural world has it that the X and
Y are the "first and second dimensions creating a" "base plane" "ground
plane" "a horizontal plane normal to gravity" on which to build a
foundation and Z is the height.

I am a sculptor, but now I spend most of my time working as it were on a
vertical screen and I get very disturbed, indeed even angry when that
screen become a digital window by which to view into a virtual world
that is in conflict with the natural order of normal logic of creation
and natural world view. The creation of synthetic world views must use
Z up as is expected in the natural order of things.

Many programers who are not experienced engineers and aviators have made
this simple mistake and it is easy to make but none the less it is
serious mistake, that causes confusion and conflict. I am sure that
this basic conflict has caused the lost of life, in fact I had very
heated conflict with my son :-)) over this very issue. It took my son
several years, he is a programer not an experienced engineer or aviator,
to understand and figure out that Z is up.

I am very excited with the work you are doing on source forge and I plan
to join your efforts..... However there are two possible problems in
basic orientation... :-))

1. Is that Z is up
2. The work that I do will be GPL + + or the Greater Good Public
License GGPL you may see the agreement at http://www.ggpl.org.

Future plans concerning XD work:
I plan to translate this basic 3D work to Japanese, Chinese at the very
least and possible to French and Russian also.
It is a small part of the work on creating a multidimensional synthetic
CAD, that I have been planned for the last 9 years based on functional
representation. F-rep. See web site http://www.hyperfun.org.

From: "Martin Baker"
To: "Carl Vilbrandt"
Subject: Re: [mjbworld - Open Discussion] I would like to work on this project
Date: 26 June 2002 07:51

Hi Carl,

> I would like to collaborate with you in your work,
That's great, this is such a big subject, there is so much to do. Lets
coordinate our work rather than duplicating effort.

> I know you are going to not
> agree with me and most likely be angry at me not believe me ect...., but
you
> have made a very big mistake, that is more important to the application of
3D
> space and computer simulation than you know.
> Z is up in engineering, and aviation.

I think it is important to question all our fundamental assumptions, so I am

I can see both sides of the argument, for example I could argue that as we
live on the surface of the earth we tend to look at things from the side
more often than we look down on them, but I take your point that in
engineering X,Y are the plan coordinates.

For me the most important argument is that my program uses Java3D, OpenGL
and/or Direct3D is to use the same standards that they use. Also I assume
that most users would want to interwork with the common 3D file formats

As you point out its not difficult to do the conversion. What I would like
to do, is allow different user interfaces to be plugged into the program, so
there could be a engineering/CAD user interface and a user interface that
uses the standards used by other 3D programs. Internally for the core of the
program I would like to use the same standards as Java3D, OpenGL, Direct3D
and most file formats. Do you think this would be a practical solution?

> 2. The work that I do will be GPL + + or the Greater Good Public License GGPL
> you may see the agreement at http://www.ggpl.org.

I am not an expert on licences (In fact I don't claim to be an expert on
anything!). I used GNU as it seemed to be the most common licence and I
would like to get my program distributed with Linux. I had a look at the
link above and it looks like GGPL does not give users the right to modify
the code, whereas GNU allows code to be modified provided that the modified
source is made publicly available on the same terms. Is this correct?

> I plan to translate this basic 3D work to Japanese, Chinese at the very least
> and possible to French and Russian also.

If you translate any of my pages, please send me a copy so that I can make
them available on my website.

Thank you for your thought provoking message and please don't be angry!

Martin