Subject:
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Re: Line in the Sand
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Newsgroups:
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lugnet.cad.dev
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Date:
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Tue, 14 Dec 1999 12:08:27 GMT
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Viewed:
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2825 times
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Steve Bliss wrote...
> In lugnet.cad.dev, Lars C. Hassing wrote:
>
> > Steve Bliss wrote in message ...
> > > Decorations on transparent parts shows through when looking at the part from
> > > behind. If the decoration polygons were put through the BFC-check, they would
> > > be clipped in this situation, because the decoration is facing away from the
> > > viewer.
> >
> > Remember BFC must be disabled for transparent parts. That's what
> > If 32 <= Color And Color <= 47 Then AccumClip = FALSE
> > takes care of.
>
> Hmm. that makes me wonder if the logic of turning of BFC clipping when a part's
> color is transparent will really work. Because a part may have the main color
> as 16, and some sections are hard-coded to a transparent color. In this case,
> the suggested logic would fail to cull correctly.
If IsTransparent(Color) Then AccumClip = FALSE
takes care of solid non-16 colors (decorations) in parts used transparently.
And a similar check added to BFC() can take care of transparent non-16
colors in parts used as solids.
So the logic is OK again.
> > > 7 If 32 <= Color And Color <= 47 Then // This restriction may or may not be
> > > 7 AccumClip = FALSE // required, depending on the style of
> > > 7 End If // rendering for transparent surfaces.
> >
> > What do you mean with the comment?
> > That dither-transparency can use BFC?
>
> That is correct.
>
> > Well, in that case we do need
> > double-sided sections for decorations!
>
> That's what I was thinking. :)
On second thoughts I don't think we need double-sided sections for decorations.
If a rendering program wishes to use BFC together with dither-transparency, it
can easily investigate whether there are non-16 colors in a transparent part.
We should not put an unnecessary rule on the part author.
> > In Danish we have a noun (vrang) meaning "wrong side" or "reverse side".
> > I can't seem to find a similar English noun.
>
> Do you mean inside-out or back?
I mean the inner surface. Like the "internal surface" of a sweater or a stocking.
If you don't have a similar noun/substantive/notion in English I can understand
why the subject is difficult to discuss, because we think/conceive differently
(as our spoken languages reflect) about the "inside surface".
/Lars
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Message has 1 Reply:
 | | Re: Line in the Sand
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| (...) Yes, it would render correctly, but it would also disable clipping more often than is required, in the case of mixed solid and transparent sections. Think of a submodel where the author used color 16, and the person using the submodel renders (...) (25 years ago, 14-Dec-99, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Line in the Sand
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| (...) Hmm. that makes me wonder if the logic of turning of BFC clipping when a part's color is transparent will really work. Because a part may have the main color as 16, and some sections are hard-coded to a transparent color. In this case, the (...) (25 years ago, 10-Dec-99, to lugnet.cad.dev)
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