Re: gEDA-user: arcs in pcb

[Mark Rages <markrages@xxxxxxxxx>]

On Fri, Jan 29, 2010 at 10:50 AM, Peter Clifton <pcjc2@xxxxxxxxx> wrote:
> On Fri, 2010-01-29 at 09:00 -0600, Mark Rages wrote:
>
>> Assuming: largest arc is 24 inches, and the desired precision 1e-5 inches.
>
> A gentle very gentle curve would require more, but certainly the above
> would be large enough for most of the applications I've seen for PCBs
> which have rotational symmetry.
>
> Arguably we can get away with quite a bit less precision for large
> geometry parts. 1e-4" would probably be fine, if not 1e-3".
>
>> Then the precision of the smallest angle is (1e-5)/24 radians or
>> 2.38*10-5 degrees.  To be safe, the new units should be millionths of
>> a degree, so one revolution is 360000000.  Sounds good?  Or a
>
> The maximum of a 32bit (signed) integer is:
>
> 2147483647
>  360000000
>
> So that wouldn't have an issue representing the number.
>
>> double-precision floating-point would maintain more than sufficient
>> accuracy over the (0,360] range.
>
> Try to avoid floating point for storage.

Why?  I can probably find a i487 processor for you if you need one ;)

Seriously, why?  all programming languages from C on up have
facilities to parse and write floating point.  And it makes the file
more human-readable, because you don't have to do mental arithmetic to
understand a measurement.

Regards,
Mark
markrages@gmail
-- 
Mark Rages, Engineer
Midwest Telecine LLC
markrages@xxxxxxxxxxxxxxxxxxx


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