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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Fri, 7 Apr 2000 19:29:18 GMT
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Viewed:
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2529 times
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In lugnet.cad.dev, Rui Martins wrote:
> I got that, but you keep on thinking about it, without trying the other
> solution (the one which does not require the reference-chain dependence)
I've kept thinking about it, and I don't see a solution.
There are some algorithms that can figure out the normal/inverted
question in some cases, but these algorithms would be too slow to
implement in a rendering program. And they are not 100% accurate, so it
would be a bad idea to make the BFC standard depend on them.
> YES, just allow any *.dat to be BFCed for it self, no reference-chain
> dependence. If the uggly undesirable invert feature (without matrix inversion)
> is encountered, just disable cliping.
That doesn't solve the problem. There's no practical way for the
rendering engine to tell if a subfile is supposed to be inverted or
normal, without more information. The transformation matrix doesn't
have the answer.
[snipped stuff about how rendering engines can assume part-files are
right-side out]
> Ok it's a sugestion !, but it won't help performance, it will actually
> slowdown the program
Then rendering programs shouldn't do it. Perhaps that part of the
document should be moved to a "Things to think about" section?
[about using NOWIND or DOUBLESIDED to mark decoration-sections]
> The renderer does NOT need or want's to know if it is unknown or double-sided,
> it just want't to know if it can be clipped or NOT.
Good point.
> There is only one problem, the "unwanted invert without matrix inversion",
> and in that case just do what I have already said in this and a recent mail,
> disable cliping (at user option), until the file is correct.
That would kill BFC processing for the entire model. And would require
the modeler (who may not have much technical knowledge about BFC or any
other details of the guts of the DAT code) to willfully disable BFC'ing.
I'm failing to see how this would be better than telling the renderer
which files may be BFC'ed, so it can process those files as efficiently
as possible.
> The renderer will render errouneously, if the user does NOT disable cliping.
And why is this a good thing? "Let's make this great new feature, that
will either speed up processing or will mess up your rendering."
> Also if we want to be picky, we could add a config file to the renderers, so
> that they now the current know files with unwanted inversions, so that they
> could disable cliping in all the reference branchs which derived from them.
That would require the renderer to look up the flag for each file.
That'd be even slower than providing a flag in the input stream.
> But I think this is too much work, and NOT worth it, just fix the file.
You're coming from the assumption that all, or nearly all, files will be
cleaned up for BFC processing, right?
Unfortunately, your approach does not fix the problem with the DAT code
not having speces about inverted subfiles--it just tries to avoid it.
Steve
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Message is in Reply To:
 | | 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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