Re: gEDA-user: little slivers

[David Griffith <dgriffi@xxxxxxxxxxxxx>]

On Sun, 10 Jan 2010, Harry Eaton wrote:

>>>> Is there some way I can easily get rid of the little slivers of copper
>>>> left between traces when doing pours?
>>>
>>> Not without adjusting the clearance on the adjacent lines to squeeze out
>>> the slivers.  I've considered several times how to fix this, and I can
>>> see options for doing in in a post-processing step, but that's not really
>>> in line with PCB's other polygon updates,which are all done live.
>>
>> Works with my "pours" branch (which does island removal), but that isn't
>> ready for merge yet.
>
> The main branch already removes islands (at least its supposed to), so I
> presume the concern here is with "fingers" connecting to the main polygon.

Yes, these are fingers projecting off the main polygon.  My problem is 
that they seem to be below the allowable 10mil minimum.  I find them 
mostly between holes and parallel traces.  See 
http://frotz.homeunix.org/tmp/slivers.pdf for what I mean.  Look at the 
bus going underneath the 40-pin DIP and between the pins everywhere.  In 
the bus, there are very tiny slivers between the traces.  Between the pins 
are very narrow bridges.  All of these seem to be below the allowable 
minimum, yet are there.

> At present there isn't a way to enforce (or check for that matter) DRC 
> on the polygons. This is something that needs to be done. I plan to take 
> this on once I have some time to work on the code again, but that might 
> be over a year away. My basic idea for DRC enforcement is to subtract 
> appropriate lines along the border of the polygon (and its holes), 
> remove the islands, then add back lines along the new contour. This 
> should make too-thin fingers, sharp bends and pointy protrusions 
> disappear.
>
> Such an operation would be too expensive to do with every polygon edit 
> operation so it would be as separate step done during DRC or when 
> manually invoked.

This sounds like the solution.  Do you have any sample code or pseudocode 
on how to do it?

> In the mean time, if you plan to flood fill a region of many tracks, 
> then I recommend that you either fill it manually, or fixup the problems 
> manually.

I'll have to try that.

-- 
David Griffith
dgriffi@xxxxxxxxxxxxx

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