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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Thu, 21 Oct 1999 00:10:02 GMT
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Viewed:
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1748 times
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Steve Bliss wrote...
> OK, we've been discussing how to best extend the LDraw language to
> allow rendering engines to do backface-culling. We've got a pretty
> good agreement on most of what is needed. I think it would be
> productive, at this point, to work from a complete statement. That
> way, we all have a firm understanding of the disagreements. ;)
Good idea, it's hard to discuss in so many threads.
> So I've written such a document.
Thank you for the well-written summary. Well-written because I agree with
99% of it ;)
> This is a serious request for feedback, suggestions, criticisms,
> additions, and arguments. We are very close on this, let's finish it up!
Yes, too bad I'm off for an Internet-free :( 4-day week-end at the sea :)
> Matrix Inversions. Rendering engines will need to correct for • transformation
> matrices which inadvertently invert the current file. They will also need • to
> allow for situations in which the matrix is deliberately inverted.
"the current file" should be "a subfile"
> 0 CERTIFY [BFC|NOBFC]
> default: NOBFC
I think you should make it clear what "default" means:
1) absence of "0 CERTIFY", or
2) "0 CERTIFY" with no (or other) tags
Is the CERTIFY really necessary?
Presence of a CLIPPING ON should be enough.
Too many rules and required meta-commands increase the risk of forgetting
some.
> 0 WINDING [ CW | CCW | UNKNOWN ]
> default: CCW
I don't think there should be a default. You should always specify either
CW, CCW or UNKNOWN.
So DOUBLESIDED should be accomplished by CLIPPING OFF?
> The WINDING setting is a local setting, it applies only to the file in • which
> the WINDING meta-statement appears.
Or:
The WINDING setting is a local setting, it applies only to the polygons in
the file in which the WINDING meta-statement appears.
> 0 CLIPPING [ ON | OFF ]
> default: renderer-dependent
Again I am uncertain what you mean by "default"...
You should always specify either ON or OFF.
> Enables or disables clipping for the rendering. Any number of CLIPPING
> statements may appear in a file. The current clip-setting is passed down • to
> subfiles when they are referenced, giving superfiles some influence over • the
> processing of subfiles. However, the clip-setting is *not* passed back up
> from the subfile to the superfile.
Also, you could stress that, CLIPPING ON in a file has no effect if
clipping is currently off.
> The INVERT meta-statement is a flag, indicating to the renderer that the
> following subfile reference has been intentionally inverted. If the next
> command-line is not a subfile reference, the INVERT is ignored.
>
> The INVERT flag is required in addition to the actual inversion, which
> occurs within the subfile command's transformation matrix.
Or:
The INVERT meta-statement is a flag, indicating to the renderer that the
following subfile reference should have its orientaion inverted, i.e. the
inside/outside definition should be swapped.
If the next command-line is not a subfile reference, the INVERT is ignored.
/Lars
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Message has 1 Reply:
 | | Re: Line in the Sand
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| (...) Sometimes, life just sucks. ;) Have a great weekend! (...) OK. (...) Both of these. (0 CERTIFY with no tags would be a syntax error, IMO.) (...) Define necessary. ;) CERTIFY is not absolutely required, but it is logical and useful. The other (...) (25 years ago, 21-Oct-99, to lugnet.cad.dev)
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Message is in Reply To:
| | Line in the Sand
|
| OK, we've been discussing how to best extend the LDraw language to allow rendering engines to do backface-culling. We've got a pretty good agreement on most of what is needed. I think it would be productive, at this point, to work from a complete (...) (25 years ago, 20-Oct-99, to lugnet.cad.dev)
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