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Steve Bliss wrote in message ...
> In lugnet.cad.dev, Lars C. Hassing wrote:
>
> > I agree WINDING may not directly make you think about BFC, but I think
> > I argued why WINDING is enough - please comment:
> > http://www.lugnet.com/news/display.cgi?lugnet.cad.dev:3220
>
> Is there a reason you prefer
> 0 WINDING (CW|CCW)
> as the 'certify statement', rather than
> 0 CLIPPING ON
> ?
>
> Winding is local.
> Certification is sort-of local -- only the local file is certified, but the
> local setting affects whether subfiles (in the same reference branch) are
> clippable or not.
> Clipping accumulates downward on the reference branch.
>
> CLIPPING seems more like a 'certify statement' than WINDING. IMO.
I think it is nice to have the winding state expressed explicitly.
IMO part authors should be allowed to whatever winding they find
most natural to work with (though you say CCW is desirable).
It is perfectly legal to use CW, we should put no constraints
on part authors, and not at all on a matter that a program
can easily swap for you.
Winding is the most functional of the commands. The CCW or CW
is interesting. Clipping is obvious.
Once stating the winding, it is natural that you want clipping and
that you have inspected the file. So you don't need to say more.
CERTIFY implies WINDING CCW, which you have to remember.
I expect CLIPPING to be used very seldom: only for double-sided
sections (can be counted on one hand?) and for parts which you
only want to check the winding but not the subfiles (most likely you
will check both at the same time).
/Lars
PS. A few parts can be made of subfiles alone (i.e. only linetype 1).
I admit a WINDING can seem strange in such a file, so perhaps
presence CLIPPING ON should also mean "certification"
(of subfiles, the winding state is unknown). See also last part of
http://www.lugnet.com/news/display.cgi?lugnet.cad.dev:3110
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Actually, I was thinking of CERTIFY, like a enable of the specific
new metacommands.
Example:
If you have a
0 CERTIFY BFC
would mean Enable or take into account the GFC related commands. besides
the fact that it certifies that file has beeing checked for point
order (bowties) and winding.
So the certify statement is a little bit more powerfull than just stating
that it complies to the some fact.
And following this, I am in favor of replacing CERTIFY with EXTENSIONS,
since it makes alot more sence, with this reasoning.
Besides this could be a great help for DEBUG, just remove (or comment) the
CERTIFY/EXTENSION line (or remove the particular extension, when you have
more than one) and all the extension MetaCommands are ignored, without
having to comment them all.
Rui Martins
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On Tue, 16 Nov 1999, Rui Martins wrote:
> Actually, I was thinking of CERTIFY, like a enable of the specific
> new metacommands.
>
> Example:
> If you have a
> 0 CERTIFY BFC
>
> would mean Enable or take into account the GFC related commands. besides
> the fact that it certifies that file has beeing checked for point
> order (bowties) and winding.
>
> So the certify statement is a little bit more powerfull than just stating
> that it complies to the some fact.
>
> And following this, I am in favor of replacing CERTIFY with EXTENSIONS,
> since it makes alot more sence, with this reasoning.
>
> Besides this could be a great help for DEBUG, just remove (or comment) the
> CERTIFY/EXTENSION line (or remove the particular extension, when you have
> more than one) and all the extension MetaCommands are ignored, without
> having to comment them all.
>
> Rui Martins
I forgot to add that you can have a file that is 'certified', but due
to its nature (the lego part/sub-part) no clipping is applicable, but it
can have correct point order (no bowties) and a defined winding (the
default, or some expecifically insert in the file '0 WINDING CW').
And also that EXTENSION (or CERTIFY) is strictly local, does not affect
other files in the rendering tree.
Rui Martins
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