At 08:40 PM 6/7/01 -0400, Brian Guralnick wrote:
>I find that the biggest time killer are polygon planes. For this reason,
>I only fill the polygons after everything else is done. Especially with a
>slow CPU.
Polygon planes are a problem because of the huge number of primitives they
can create.
Positive/negative merge planes would not have this problem; they could be
correct by design; essentially, clearance would not have to be checked
since it would be created on the fly by the rules. However, checking
connectivity would be more difficult. Nevertheless, a well-implemented pour
process using negative copper would have a much lower primitive count and
thus faster draw, plot, and DRC times. Plus gerber files would be much
smaller, and planes could be recreated from the gerber, unlike the present
situation, which will only import a huge pile of draws.
I think the key to easy connectivity DRC would be to require actual track
connecting all nodes; what the pour would do be to fill out this track; it
would not make a connection that was not already there; it would be created
by blowing out all primitives -- other than track, arc, and direct-connect
pads and vias belonging to the pour net -- according to the appropriate
design rule, within the defined polygon; this would be superimposed over
the connection track. Thermal reliefs would be created by an actual track
pattern; the negative pour itself would not make connections to pads. Think
of it as a trace fattener.
With this facility, the dichotomy between negative and positive layers
could disappear, by allowing a layer to be defined as negative overall
(i.e., there is a "polygon" xtending over the entire workspace).
At the same time, nested split planes could be implemented. There is no
definition problem with a split plane completely contained within another,
only with, in some cases, planes which are partially co-extensive and
partially independent. Where they overlap is ambiguous. So the crossing of
one split boundary by another would generate an error.
[EMAIL PROTECTED]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433
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