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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Sun, 2 Apr 2000 23:43:19 GMT
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Reply-To:
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rui.martins@linkSPAMLESS.pt
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Viewed:
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1734 times
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> Fourth in the series, starting with message #41 in the "Line in the
> Sand" thread. Notice that I scanned past a number of messages before I
> got another 'open issue' hit. This posting covers up to & through
> message #83, the end of the thread.
>
> In <http://www.lugnet.com/cad/dev/?n=3517>, Lars points out:
>
> > 1 16 -4 0 0 0 0 0 0 0 4 1-4disc.dat
> > The determinant is zero, which BTW causes POVRay to halt
> > ("singular matrix"). L3P has to fix these matrices or POVRay
> > would not render many parts at all!
> > As part of certifying a DAT file I believe this kind of subfile
> > reference should be fixed as well, like into
> > 1 16 -4 0 0 0 1 0 0 0 4 1-4disc.dat
> > "L3P -check -w3" will help spot the problems.
>
> This point hasn't been discussed since, I believe. This is very valid,
> these "singular transformation matrices" should be fixed.
I believe that the only problem is that these matrixes can't be inverted !
I'not sure if placing a one on the specific place has exactly the
same graphic behaviour ?
can someone confirm ?
> BTW, this gives the CERTIFY tag something to define besides clipping and
> winding. In order to cleanly certify a file, it should *not* have any
> subfile commands with singular matrices.
>
> Even so, CERTIFY is still functionally redundant...
Use my proposal:
0 CERTIFY BFC MTX
where MTX is Matrix, correct non singular matrices
> ------------------------------------------------------------------------
> One other thing. Starting somewhere around message #3424
> <http://www.lugnet.com/cad/dev/?n=3424>, Lars and I got to discussing
> what purpose would be served by intentionally disabling clipping within
> a file (via the NOWIND option, if that one is preserved in the spec,
> otherwise using NOCLIP).
>
> I contended that decorations will need to be flagged as double-sided, so
> that they will show through the part when it is used as transparent.
>
> Lars responded that no clipping can be performed on transparent
> quads/tris, because some renderers will need to use the backside objects
> to provide more depth to the transparent areas, so the spec should
> explicitly require that BFC be disabled when rendering a
> transparent-colored part.
>
> I replied that that was an unreasonable solution because a part-file may
> have hard-coded transparent sections, even though the reference to the
> file is a solid color. Think of rendering <part:2634> in white. The
> renderer would have to prescan the file, to find the hard-coded
> transparent sections. And then the entire file would have BFC disabled.
Nope, the hardcoded transparent sections should have cliiping disabled,
for a BFC certifyed part/piece.
> Lars pointed out that we should not require parts-authors to code
> anything that the rendering engine can figure out for itself.
>
> And that was the end of intelligent discussion on that point.
Not always, but let's assume yes.
> ------------------------------------------------------------------------
> A side issue of that discussion: can transparent surfaces be clipped?
To be correct NO, but that can be left has an option to the user.
There is not TOO much difference, and while editing would be a nice feature
(clipping), because of speed increase, for final drawing don't disable
trasnparent clipping.
see ya
Rui Martins
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Message has 1 Reply:
 | | Re: BFC: LITS 2
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| (...) Actually, the problem is that their determinant is 0, neither positive nor negative. So the renderer would have to disable BFC processing for any file with this kind of reference. Another problem (that L3P handles in most cases) is that (...) (25 years ago, 7-Apr-00, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: BFC: LITS 2
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| Fourth in the series, starting with message #41 in the "Line in the Sand" thread. Notice that I scanned past a number of messages before I got another 'open issue' hit. This posting covers up to & through message #83, the end of the thread. In (...) (25 years ago, 31-Mar-00, to lugnet.cad.dev)
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