[LSC] Call for votes: Back Face Culling (BFC) Specification 1.0

[William Howard]

On the subject of writers, I'm happy to add anyone and everyone to the list,
or even to remove the line altogether and just leave it as authored by the
LSC

Can you supply a the list of names that should be on the writers line

thanks

W

-----Original Message-----
From: lsc-bounces at ldraw.org [mailto:lsc-bounces at ldraw.org] On Behalf Of Lars
C. Hassing
Sent: 08 November 2006 00:14
To: LDraw Standards Committee
Subject: Re: [LSC] Call for votes: Back Face Culling (BFC) Specification 1.0


About the paragraph:
Marking a file as BFC-compliant only directly affects that file. In order
for subfiles
to be treated as compliant, they must also be marked as compliant.
Additionally,
with the exception of parts, a file is only treated as being BFC-compliant
if it and all of its superfiles are compliant. The reason for this is that,
while processing, there is no way to know the intended inversion state of a
subfile
when the file's superfile isn't BFC-compliant. The reason that part files
can be excepted
from this rule is that they are complex closed solids, so there is never a
valid reason
to invert them. Assuming part files are never inverted allows the rendering
engine
to apply BFC-processing on certified parts, even if the calling file(s)
(for example, the main model file or sub-models of the main model) aren't
certified.


I think it should be made more clear that renderers can treat models
as implicitly certified and apply BFC to the parts they reference,
either directly or via submodels.
If models contains line type 3 or 4, or references primitives,
these cannot have BFC applied (unless the model is explicitly certified).

Parts are objects with obvious orientation. You are not in doubt what is
inside/outside of a part!
Because the orientation of parts is natural and intuitive, certified
parts would be the right place for enabling clipping.
And it would be safe and legal to do so, because rendering programs
should keep track of transformation-inversions, i.e. you can safely use
mirrored submodels.

See also
http://news.lugnet.com/cad/dev/?n=3424
scroll down to "Sorry, I didn't make myself clear."

Could you English writers please try to explain that in "plain English".


About "writer":
I recognize Steve Bliss (and others) did a great job in actually
writing all thoughts and comments together to the final doc,
but I also feel that I and others have put a great effort
into the original discussions, e.g.
http://news.lugnet.com/cad/dev/?n=3156&t=i&v=c
and before that.
I was especially eager to have the syntax right
because I implemented BFC in L3Lab at that time.
So maybe we can deserve a little credit too somehow...

Otherwise I think we have a fine spec now,
so I vote YES.
/Lars


William Howard wrote:
> Background:
> 
> The LSC adopted the de-facto BFC standard as their draft BFC standard
>
(http://www.ldraw.org/modules.php?op=modload&name=News&file=article&sid=217)
> and have since been working to clarify a few ambiguities.
> 
> The current working version of the BFC specification can be found here
> (revision 1, version 4)
> (http://www.ldraw.org/index.php?name=News&file=article&sid=408)
> 
> 
> ------------Beginning of proposal----------
> That the LSC adopts the BFC standard as given at
> http://www.ldraw.org/index.php?name=News&file=article&sid=408 as the first
> version of the official BFC standard
> and publishes it as such.
> ---------------End of proposal--------------
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