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Re: gEDA-user: General Layers questions



On Mon, 2011-02-14 at 04:04 +0100, Kai-Martin Knaak wrote:
> Martin Kupec wrote:
> 
> > It is not possible to unmask general shape. There is the possibility
> > with converting rectangle to pad, but that is probably not the best way.
> > Is the right way to have a layer of "negative soldermask". Pads and pins
> > will be there automatically and you would be able to add any shape
> > there? Or something else is better?
> 
> IMHO, "negativeness" should be a property of objects, not something 
> specific to a layer. I'd like to draw positive and negative lines on 
> anything, be it copper, or mask.

Gerber output only really works well if you a layer which is made up of
negative or positive primitives. Other tools I've encountered use
negative layers for things like planes (where tracks define the
clearance separation between planes). The difficulty is that you can't
easily have "this bit as negative" + "this bit as positive".

I guess we can do better than other tools in some cases, but the output
might be a lot more polygon-y than would be otherwise achievable with a
pure positive or negative layer. I suppose if it matters, we could let
the user emit output in either form. (Assuming objects on the layer make
that possible). Fallback to polygons could always work I guess.

-- 
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!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)

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