Re: gEDA-user: Re: Some pcb pecularities

[joeft <joeft@xxxxxxxxxxxxx>]

Kai-Martin Knaak wrote:

> On Wed, 17 Jan 2007 11:20:00 -0500, DJ Delorie wrote:
>
>  
>
> > > 3) Auto router and manual line drawing tool interpret line clearance
> > > differently. If clearance is set to 10 mil for a particular route style,
> > > the auto routed lines will punch a 10 mil gap into polygons. With manually
> > > drawn lines the gap is just 5 mil. I'd say, the auto router is correct. 
> > >      
> > According to the documentation, "clearance" is the amount added to the
> > thickness of the line, so a 10 mil clearance should result in a 5 mil
> > gap on each side of the line.  At least, that's what the file format
> > spec says.
> >    
>
> Sorry, I confused manually and auto routed tracks (see the other post). So
> it seems the autorouter acts according to the file format spec. Meanwhile
> the manually routed tracks follow common sense ;-) Anyway, both should act
> the same.
>
>
>  
>
> > > 4) Rubber band move of automatically generated vias results in a mess of
> > > tracks. Some tiny tracklets seem to be expanded rather than moved. 
> > >      
> > Have you tried running the optimizer after autorouting?
> >    
>
> This is about manually routed tracks with vias inserted on the fly after a
> change of layers. I tried the optimizer anyway, but to no avail. The mess
> seems to occure only, if there are short tracks completely hidden under
> the via.
>
> ---<(kaimartin>)---
>  
This item (4) is (I believe) due to a bug that is most often seen when 
there are short segments (as you mention above) and often where the 
spacing between vertices is near to or smaller than the grid spacing or 
the line width is close to (2*grid spacing).  What is happening is that 
it is picking the wrong end (vertex) of some of the short segments and 
moving them  Picture 3 line segments spanned by 4 vertices (A,B,C,D).  
A-B and C-D are relatively long, while B-C is shorter then the line 
width.  If you try to move segment C-D or vertex C it looks like it 
selected vertex B instead.  (This is easier to draw than describe:).  It 
is not an issue with automatically generated vias, the key is simply 
having short line segments.   We looked into this several months ago and 
figured out part of the problem.  A bug was entered on SF at the time 
but has not been looked at since as far as I know.  I run into this one 
all the time and find it really annoying.

Joe T


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