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Date: Tue, 2 Feb 2016 10:28:31 +0100
From: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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Subject: Re: [geda-user] The nature of gEDA layers
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> > Currently, the PCB objects come with a lot of implicit aura
> > attached, polygon clearance, soldermask clearance, solderpad,
> > thermals, ...
> > 
> > A generic geometry may need to be more explicit.
> > 
> > Everything is drawn at a depth.  There are positive and negative
> > depths. Deeper stuff is drawn before shallower stuff.  Negative
> > depth draw holes and clerances.
> > 
> I feel like this is the kind of magic that looks elegant and generic 
> on inception but tends to turn into an obstacle further down the 
> evolution of the application. Specifically:

Depth I consider a little bit confusing for use in pcb/gpcb.

> * In addition to positive and negative, there may arise the need for a 
> third mode of drawing. E.g. XOR-drawing. (No, I don't know what XOR-
> draw would be good for in the context of EDA -- just brain storming)

There is something similar as xor in gerber file format, inverting polarity I think. To draw material and cut out would however be useful. Clearance in polygon in sort of make cut out but it is not possible to draw cutout manually. For layer via/board it would make sense with other forms of cut out than round for drilled holes.

> 
> * The depth parameter kind of enforces the way how to render the 
> design. It would be more flexible and potentially easier to extend to 
> mark-up the intended meaning.

Layers are one pixel "thick" and stack up is used for order. It would be possible with more than on bit thick or more colors for different materials, it may add complications or solve overlapping problem which may occure if using two layers for one mechanical position.

> ---<)kaimartin(>---


Nicklas Karlsson