Re: gEDA-user: layers for pcb

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Fri, 2010-09-10 at 17:41 -0500, John Griessen wrote:
> On 09/10/2010 05:20 PM, Peter Clifton wrote:

> The thing we are now calling layer group seems what Andrew wants to call a layer.
> Then you'd still have intermediates and what to call them?

I think layer groups as a way of partitioning different tracks / zones
on the board is more limited than tagging with attributes.

I realise there are a lot of Unix fans here, so this analogy isn't
perfect to make my point.. but think unix group based permissions vs.
ACLs.

Either system can do what you want, but with groups / layer groups, you
end up needing to create a lot of them (for PCB, layers within a group),
and management of them can get a little out of control.

From a technical point of view.. using lots of layer groups is also bad
for performance, (not sure how much you'd notice though), since the
r-trees of objects are stored per layer, and search complexity would
seem to go up with unfavourably with increasing numbers of sub-groups.

> Anti-layer isn't my favorite.  I'd call some of the intermediates cut-sets or cut-layers.
> Layer group as a name doesn't bother me.

The composition / z-order rules will be important to define and get
right whatever we do, be it with anti-objects, or cutting layers.

Do the anti-objects / layers clear every type of object? (Polys /
Lines / Pads?), or do they only act on (say) polygons?


-- 
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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