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 CAD / Development / 6697
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Subject: 
Re: L3P user primitive substitution
Newsgroups: 
lugnet.cad.dev
Date: 
Thu, 3 Jan 2002 20:16:08 GMT
Viewed: 
1381 times
  
Since there hasn't been discussion of this topic, and more than two weeks
have elapsed, can we assume that:

A) The proposed revision is acceptable
B) The proposed revision is un-acceptable
C) No one knows

LMKWYT,
Steve

In lugnet.cad.dev, Steve Bliss writes:
> Dear All,
> 
> Currently, there are a number of files on the Parts Tracker which include
> embedded POV-Ray, using the 0 L3P meta-statement.
> 
> I've been emailing with Lars, Paul and Chris about some concerns I have with
> this approach.  Basically, before we allowed this approach in the official
> parts library, I wanted to be sure we were taking the best approach.
> 
> Through the email, I've been convinced that embedding POV-Ray code in part
> files is a good idea.  The alternatives would be:
> 
> 1. Not address the issue at all, and not support any method for substituting
> solid-modeling code for LDraw code.
> 2. Maintain a separate library of POV-Ray files, or at least a separate
> library POV-Ray enhanced LDraw files.
> 
> I don't think either of these alternatives is desireable.
> 
> One issue I still have is with the specific syntax used.  I think the
> current syntax is too specific to L3P.  What would be better is a more
> generic meta-statement, that could be used for other purposes in the future.
> 
> So I'd like to propose that the current syntax be replaced with the following:
> 
> > 0 IFDEF <tag>
> >  Conditional section begin
> >  Begin non-LDraw statements in comment statement fields
> > 
> > 0 IFNDEF <tag>
> >  Conditional section begin
> >  Begin DAT statements
> > 
> > 0 ELSE
> >  Switch between above section modes
> > 
> > 0 ENDIF
> >  Terminate conditional section
> 
> In the current situation, <tag> would always be POVRAY.  In the future,
> other possible tag-values may be determined, such as level-of-detail settings.
> 
> So, that's all I've got to say for now.  Comments, anyone?
> 
> Steve
> 
> In lugnet.cad.ray, 12 months ago, Chuck Sommerville writes:
> > Awhile back, I persuaded Lars Hassing to add a feature to L3P.  I wanted the
> > ability to substutite POV language commands in the comments of a .DAT file
> > that could be used in place of the DAT primitives when rendering through
> > POV.  This would allow users to add native POV commands that could render
> > better than the triangles and polygons defined  in DAT files.  Since the
> > commands are inbedded in comment fields, and only recognized by L3P, they
> > have no effect of any other tools.  Lars was waiting untill I tested the
> > commands to announce the feature.  The good news, is you probably already
> > have the ability to use these features.  He built them into Version 1.2
> > 20000616.
> > 
> > The commands are
> > 0 L3P IFPOV
> >  Conditional section begin
> >  Begin POV statements in comment statement fields
> > 
> > 0 L3P IFNOTPOV
> >  Conditional section begin
> >  Begin DAT statements
> > 
> > 0 L3P ELSEPOV
> >  Switch between above section modes
> > 
> > 0 L3P ENDPOV
> >  Terminate conditional section
> > 
> > After running L3P, you can see in the POV file conditionals like
> > if(0) or if(1)
> > To see the alternate version for comparison, just change the constant in
> > these conditionals.
> > 
> > If you don't understand any of this, don't worry,  I am following this post
> > up with some examples.  Remember to get L3P V1.2 or latter to use thse.
> > 
> > -Chuck



Message has 2 Replies:
  Re: L3P user primitive substitution
 
(...) C! But it does not seem completely unacceptable to me. Play well, Jacob (25 years ago, 4-Jan-02, to lugnet.cad.dev)
  Re: L3P user primitive substitution
 
(...) A: I like it. -Chuck (25 years ago, 4-Jan-02, to lugnet.cad.dev)

Message is in Reply To:
  Re: L3P user primitive substitution
 
Dear All, Currently, there are a number of files on the Parts Tracker which include embedded POV-Ray, using the 0 L3P meta-statement. I've been emailing with Lars, Paul and Chris about some concerns I have with this approach. Basically, before we (...) (25 years ago, 17-Dec-01, to lugnet.cad.dev)

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