Nostalgia trip

[Bob Bradlee]

On Mon, 10 Mar 2008 11:25:55 +0000, Roger Holmes wrote:

>There are issues using 2Pi  
>because of rounding errors. Usually you end up having tolerance  
>values. Without tolerances, if someone rotates something by 90  
>degrees four times, they don't QUITE get what they started with when  
>using 2PI, but with degrees, they do.


Were are not talking about rotating an image here just projecting one.


>As for representing an infinite number of angles, don't be silly.  
>Especially if you are using tolerances.

Point taken :-)

You also pointedout corredtly that floating point hardware was not always available.

We were punching fixed-point CAD data on 80 col cards and plotting bed sheets on a flatbead plotter, it 
was "old" when I first worked with it in the mid 70's at Western Electric. 

BTW: radians work fine with fixpoint provided you are not rotating things that were previously rotated.

Back to topic, I think the subject was displaying tesx on a vector screen. 
In the 1960's Dr. A.V. Hershey of the Naval Weapons Laboratory while working with the U. S.. National 
Bureau of Standards created the Hershey's Repertory of Occidental Type Fonts. This is the origional data 
set I used when I built the CADfont set for AutoCAD that became the extened font set and package with 
the product.

Over the years many conversions/translations have been made, somewhere around here I have a copy 
coded in (lisp) for driving a flame cutter. Check it out, and yes it is interger vector based ....

Here is a google link for more info:

http://tinyurl.com/36un8h

Back under my rock ...

Bob