Re: gEDA-user: General Layers questions

[Martin Kupec <martin.kupec@xxxxxxxxx>]

On Fri, Mar 18, 2011 at 01:44:35PM -0600, John Doty wrote:
> >> Trying to model things that aren't layers as if they were layers is
> >> one common mistake in this kind of tool. Equally common is leaving out
> >> layers: the insulating layers in a PCB are just as important as the
> >> copper, and have their own properties (shape, thickness, material,
> >> etc.). They're a critical part of the layer stack.
> >> 
> >> The description language needs to be able to express "feature p in
> >> layer x is aligned with feature q in layer y" in order to build up
> >> composites. This is the geometrically sensible way to describe the
> >> result of drilling through several layers. But the geometric
> >> description language should not be tied to any particular fabrication
> >> procedure.
> > 
> > This is all too physikal for my taste.
> 
> I assert that if you do it any other way, you wind up with the following catastrophe: the code for every layer type needs to incorporate a specific definition of its interaction with the code for every other layer type. A total collapse of factoring, poisoning flexibility and maintainability. But if layers correspond to actual geometric layers, this can be avoided, I believe.

Actually what I am trying to do, is to have concept so layers don't
interract with layers of different type. The composits are a bit
problem, because I would need to consider more layers when performing any
action, but I think that it can still be interaction with object on the
same layer.

So, i.e., If we would have 'hole' layer. I would have check, that holes
on hole layer are not intersecting. And also check the intersection of
attached shapes on each layer. But all what can happen is that some
layer will yell that something bad happend and I should cancel my
action.

	Martin Kupec



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