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@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user