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Date: Mon, 13 Jul 2015 08:40:11 +0000 (UTC)
From: "Cirilo Bernardo (cirilo_bernardo AT yahoo DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: "geda-user AT delorie DOT com" <geda-user AT delorie DOT com>
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Subject: Re: [geda-user] PCB interface (ECAD vs. MCAD)
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----- Original Message -----

> From: "Chris Smith (space DOT dandy AT icloud DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
> To: geda-user AT delorie DOT com
> Cc: 
> Sent: Monday, July 13, 2015 6:07 PM
> Subject: [geda-user] PCB interface (ECAD vs. MCAD)
> 
> Out of interest, does anyone know why there is so much dissimilarity between 
> ECAD and 2D MCAD tools?  It seems to me that PCB layout is just MCAD with added 
> semantics: connectivity between objects and relationships between layers.  In 
> fact if I had to develop a PCB layout program I’d probably start with something 
> like QCad and add electrical semantics.
> 
> The typical MCAD interface seems to have everything I’d want in terms of 
> interface:
> * precise drawing tools: snapping and positioning.
> * duplication and arrangement of objects.
> * scripting.
> * blocks (footprints) with arbitrary shapes on multiple layers.
> 
> Is there anything about MCAD that makes it particularly unsuited for PCB layout?
> 
> Regards,
> Chris
> —
> Chris Smith <space DOT dandy AT icloud DOT com>
> 

MCAD and ECAD only share a few (mostly trivial) things in common;
for the most part they are really very different domains and
different problems need to be solved. For ECAD you want to do
checks on networks to ensure that there are paths between
given nodes - this is a requirement both for a useful schematic
editor and a PCB layout program but rarely of interest in MCAD;
the exception perhaps is if you're working on a network of pipes
to distribute some fluid - but typically in such cases you'd use
the MCAD to create the physical model of a system and some other
more specialized software to do the analyses. Now generally these
days if you say "MCAD" you're talking about 3D solid model design
software; if you're doing 2D stuff that's simply drafting software
and not necessarily MCAD although no one will dispute that it's
CAD.

Otherwise the only significant feature I can think of which is
shared by ECAD and MCAD is the 2D geometry code needed to create
outlines/cutouts/fills in the PCB design phase. I guess MCAD
would also do clearance checks so you could script it to do
DRC on 3D models of tracks if you really wanted to do things the
hard way.

- Cirilo