Subject:
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Re: BFC: LITS 2
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Newsgroups:
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lugnet.cad.dev
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Date:
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Mon, 3 Apr 2000 22:39:21 GMT
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Viewed:
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1797 times
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In lugnet.cad.dev, Rui Martins wrote:
> > At the least, the standard should say, "the BFC options must be
> > explicitly declared in each file. If a file has an invalid declaration,
> > the rendering engine should assume X and Y."
>
> Agreed! but that's NOT currently written that way, is it ?
No, it isn't. BUT, there is very little functional difference between
what is currently written and the suggestion above. As far as the
function of a rendering engine is concerned, there is no difference --
if a file doesn't specify the options, the renderer will use assumed
values.
> > In <http://www.lugnet.com/cad/dev/?n=3195>, Rui wrote:
> >
> > > check the following two statements:
> > > ---------------------------------------------------------------------------
> > > > To make this standard useful and effective, the LDraw parts library
> > > > must be updated to follow the new standard. Since it would be difficult to
> > > > rewrite the entire library in one update, the standard will allow for a
> > > > mix of extended and unextended files in one rendering.
> > >
> > > ---------------------------------------------------------------------------
> > > > 2 Allowable Clipping. A subfile can only have clipping applied when the
> > > > 2 following conditions apply:
> > > > - All superfiles are certified.
> > > > - The current file is certified.
> > > > 2 - No superfile has disabled clipping prior to referencing this
> > > > 2 subfile.
> > >
> > > ---------------------------------------------------------------------------
> > >
> > > Allows a mix of extended and unextended files in one rendering, but
> > > to allow clipping, all files, have to be certified !?!?
> >
> > This is an issue of language in the document. The second quoted passage
> > was updated to read:
>
> NO it is NOT ! read on.
Yes, this specific issue (comparing the two pieces of text), is at most
a language issue. The two sections are not contradictory, they are
unclear. The first section simply says that a model (that is, a
collection of multiple DAT files) may include both certified and
uncertified files. The second section says that when a subfile is
rendered, all superfiles in the reference-chain must be certified in
order for the subfile to be BFC'ed (along with the other conditions).
> > |4 Clipping. It must be possible for a file to enable and disable clipping. But
> > |4 even when clipping is enabled locally, it may not be possible to perform
> > |4 clipping on the file in some circumstances. Any file will have clipping
> > |4 applied only when the following conditions apply:
> > |4 - All superfiles (in the current reference branch) are certified.
> > |4 - The current file is certified.
> > |4 - No superfile has disabled clipping prior to referencing this
> > |4 subfile.
> > |4 Unless all of these conditions are met at the time a subfile is rendered,
> > |4 no clipping is possible.
>
> I know that the branch only would be required, but I don't agree with
> this, it's too restrictive, withou need for it.
Do you have a solution for it?
> > > > In some cases, it may be desirable to assume that a file is
> > > > right-sideout, (and therefore clippable) even though not all superfiles
> > > > are certified. One obvious example is files in the ldraw\parts
> > > > directory.
> > >
> > > This paragraph is another one, sorry to say this, but IMHO
> > > this paragraph it's a mess. (Could someone explain better !?)
> >
> > This section was rewritten as:
> >
> > |7 Assumed inversions. Generally, it is not possible to assume that a subfile
> > |7 is inverted or normal (which is the reason for the 0 BFC INVERTNEXT meta-
> > |7 statement). One important special case is this: model files do not invert
> > |7 part files. Parts are complex files which would be essentially useless if
> > |8 they were inverted. Assuming part files are never inverted allows
> > |9 the rendering engine to apply BFC-processing on these parts (assuming the
> > |9 parts are certified), even if the calling files aren't certified.
> > |7
> > |7 No assumptions can be made about models which make direct use of primitives
> > |7 or polygon commands, so a rendering engine should not simply treat uncertified
> > |7 model files as certified.
>
> More processing clutter ! Undesirable
No rendering engine has to do this (make assumptions about references to
file in the parts directory). It is included in the spec as a
suggestion for one way to improve performance.
> First, Use comments, instead of clutering the BFC extension, and
> disable CLIP in the section.
Huh? I don't understand what you mean.
> Second if the "All branch must have cliping on to BFC" was NOT used, ideia
> which I'm in favour, then no cliping info would be passed to references.
That would be nice, but you haven't said how we're supposed to get
around the problems.
> > In <http://www.lugnet.com/cad/dev/?n=3211>, Lars wrote:
> >
> > > Also there should be some words about using 0 CLIPPING OFF for a
> > > double-sided
> > > section of a file.
>
> Use comments, not Meta-commands, they will inder performance if use when
> NOT absolutly required.
I don't understand what you are saying here.
> > This is an open issue. It's noted at the end of the document. That
> > should be moved to the top.
>
> BIG Open Issue ! wouldn't you say ?
>
> It affects the entire way of processing files!
I wouldn't say this is a big open issue, because Lars was discussing the
need for documentation of the method, not discussing the methodology
directly.
Steve
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Message has 1 Reply:
 | | Re: BFC: LITS 2
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| (...) OK, I just stated that this isn't written as said above, maybe it would be clearer if it was, but I undestood it from the "proposed spec". [...SNIP...] (...) [Mind Drill ON 8) ] I got that, but you keep on thinking about it, without trying the (...) (25 years ago, 4-Apr-00, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: BFC: LITS 2
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| (...) I agree with the default from the start, I proposed them, somewhere ! (...) Agreed! but that's NOT currently written that way, is it ? (...) NO it is NOT ! read on. (...) I know that the branch only would be required, but I don't agree with (...) (25 years ago, 2-Apr-00, to lugnet.cad.dev)
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