Re: gEDA-user: pcb, how to remove mm garbage (very short lines)?

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Wed, 2008-11-19 at 22:59 +0100, Stefan Salewski wrote:
> Am Mittwoch, den 19.11.2008, 16:37 -0500 schrieb DJ Delorie:
> > > Important may be the correct mapping of user input to internal pcb
> > > coordinates.
> > 
> > The problem is rounding - some grid points round up, some round down.
> > You end up with off-by-one bugs, no matter how "precise" you are,
> > unless you can avoid the need to round completely.
> > 
> 
> I see that rounding can be a problem.
> 
> I think that pcb program should always use its internal coordinates for
> calculation and for its grid. If each user input (mouse click) is mapped
> to this exact grid position (which is an integer multiple of pcbs
> internal units) it may work. Of course, if user input is first mapped to
> a mm grid, than rounded, rounding errors and problems may occur.
> 
> If user select i.e. 0.25 mm grid, pcb program should use a 0.01 mil
> based grid which best fits a 0.25 mm look.

Fine over a small component, however if you're trying to position
mechanical items on a large board, you don't want accumulated drift.
(This said.. perhaps it would still be acceptable if the internal units
are small enough).

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user