SUO: Use of 2-D representations

[Tim King <tmk@LSC.CO.UK>]

Title: Use of 2-D representations

Dear Patrick,

I think that you miss an important point;  in principle, the CADCAM system holds the master 3-D model and generates any necessary 2-D view according to rules.

Cheers,
Tim.

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* Dr. Timothy M. KING   CEng MIMechE PhD DIC ACGI
* Executive Consultant, Technology
* LSC Group, Concept House, Victoria Road, TAMWORTH, UK - B79 7HL
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> -----Original Message-----
> From: Patrick Cassidy [mailto:pcassidy@bellatlantic.net]
> Sent: 30 October 2001 02:51
> To: West, Matthew R SITI-ITPSIE
> Cc: cassidy@micra.com; Adam Pease; Seth Russell; John.Velman@HSC.com;
> standard-upper-ontology@ieee.org; Frank Farance
> Subject: Re: SUO: RE: 4_d vs. 3-D views
>

<snip>

>    I can't resist, however, commenting on one of your
> points:
>
>  >
>  > MW: Let me try an analogy on you. It used to be that the only
>  > sort of drawing you could have for an engineered object would
>  > be 2D. With the advent of computers, it became practical to have
>  > a 3D representation. The 3D representations did not really
>  > hold much information that could not be held in the 2D
>  > representations, but some things like clash detection (2 objects
>  > occupying the same space) became very much easier. You will not
>  > be surprised to hear that 2D drawings are now little used to
>  > represent complex physical objects.
>  >
>
>      For product designers with access to CAD-CAM programs,
> that may be
> true. Yet, people still find 2-D views in printed publications highly
> useful, and I suspect that even those with access to CAD-CAM programs
> use 2-D drawings between each other for some non-trivial exchange
> of information.  Specifically, when 2-D is adequate for a purpose,
> using 3-D may just waste time and effort.  More to the point, when a
> person **looks** at a physical object, it is the 2-D view (or 2-1/2-D)
> that is seen, with no interior parts, and people are used to
> comprehending objects with such a mental image in mind. 
> Likewise, when
> a person **looks** at an object, it is the instantaneous
> object that is
> in view at any one time point, and that may be why some of us
> feel that
> the 3-D view is more "natural".  For myself, I have always been
> uncomfortable trying to envision a whole 4-D object when I
> can only see
> a temporal part (the future part is invisible, except in possible
> worlds). This is quite different from a computerized CAD-CAM image,
> which can have the whole 3-D object in view.

<snip>