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 CAD / Development / 2952
    Re: Hidden surface removal, and vertex order in part/primitive DAT files —Jacob Sparre Andersen
   Michael Lachmann: (...) I think we agreed to use 0 CW and 0 CCW lines in the beginning of the files to indicate (C)CW compliancy, but you should have a look at what Steve actually has written in his parts. (...) It would be very nice if you (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
   (...) I'm willing to change my parts, if the standard changes. Assuming parts which are *not* C(C)W need to be flagged at all. (...) I agree completely. Steve (25 years ago, 1-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Leonardo Zide
   (...) I guess we could at least decide to use CCW to determine the normal of a face, unless there's someone who prefers to use CW ? Leonardo (25 years ago, 1-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Gary Williams
    Leonardo Zide wrote in message <37F4ECA7.C0BFCF7D@c...com.br>... (...) I'd vote for CW for two reasons: 1) 'Clockwise' is shorter than 'counterclockwise'. 2) CW is used more often than CCW in rendering applications (to my knowledge) because the (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Leonardo Zide
   (...) I can't argue with that :) (...) No way ! The front faces are CCW in 3DS Max, and quoting the OpenGL 1.2 specs. for glFrontFace() "mode: Specifies the orientation of front-facing polygons. GL_CW and GL_CCW are accepted. The initial value is (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Michael Lachmann
   What if say a complient file contains anything starting with "0 CW". Any program dealing with this information could just scan for "0 CW*". We also could use a tag "0 AW*" if why ever the orientation is not clock-wice but anti-clockwice .... I think (...) (25 years ago, 2-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Gary Williams
    Michael Lachmann wrote in message ... (...) I retract my earlier suggestion. I'd prefer to test for '0 CW-compliant' than '0 CW*' because checking for an exact string match is usually easier. Not supporting wildcards also promotes consistency. (...) (25 years ago, 2-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Jacob Sparre Andersen
     Gary Williams: (...) I still think using 0 FACE ( CW | CCW | DOUBLE-SIDED | UNKNOWN ) is most practical. Play well, Jacob ---...--- -- E-mail: sparre@cats.nbi.dk -- -- Web...: <URL:(URL) -- ---...--- (25 years ago, 2-Oct-99, to lugnet.cad.dev)
    
         Re: Hidden surface removal, and vertex order in part/primitive DAT files —Gary Williams
       Jacob Sparre Andersen wrote in message ... (...) That works for me. I don't suppose there's an official standards-setting body of people charged with voting on extensions to the .dat format, is there? Maybe it's time to form one. -Gary (25 years ago, 2-Oct-99, to lugnet.cad.dev)
     
          Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
      (...) We're it. So to speak. Steve (25 years ago, 3-Oct-99, to lugnet.cad.dev)
    
         Re: Hidden surface removal, and vertex order in part/primitive DAT files —Michael Lachmann
      Jacob Sparre Andersen wrote in message ... (...) also (...) but (...) the (...) an (...) Is this the standard now, or at least could we make it the standard ???? Mike (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
     (...) That's what we're doing now--figuring out what the standard should be. Both the function and the syntax. But "standard" is an odd term in this case. In my mind the LDraw standard is defined as "code which is recognized and interpreted by (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
     (...) Forgot the footnote: 1- There's an interesting distinction between 'valid' and 'well-formed' contructions. LDraw will allow line-breaks as whitespace in commands, so: 1 16 0 0 0 1 0 0 0 1 0 0 0 1 3001.dat is valid, but it's not well-formed. (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
   (...) 578 is compliant because it contains *only* subfile references, which have been verified to not mess up (C)CW-ness. But that doesn't mean the *subfiles* are compliant. It also assumes the compliant subfiles are oriented the way the author (me) (...) (25 years ago, 3-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Michael Lachmann
   Steve Bliss wrote in message <37f6c258.270062819@...et.com>... (...) 30 (...) Does that mean if a program would find the CW directive it can assume that every-thing in this file is compliant? E.g. the program would not have to test if possible (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
   
        Interpreting the proposed FACE meta-command —Gary Williams
     Michael Lachmann wrote in message ... (...) Here's my take on the matter. The meta-command: 0 FACE <CW|CCW|DS|UNKNOWN> ...should only be used to indicate the order of the vertices of the polygons _in the file that contains it_. If A.dat has a '0 (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Interpreting the proposed FACE meta-command —Jacob Sparre Andersen
     Gary Williams: (...) Very sensible (now that Steve has convinced me). (...) Hmm. I don't like it, but we have already abbreviated (counter)clockwise, so it does make sense to abbreviate double-sided too. :-( Play well, Jacob ---...--- -- E-mail: (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Interpreting the proposed FACE meta-command —Gary Williams
       Jacob Sparre Andersen wrote in message ... (...) I was just trying to be consistent...:) I'd be just as happy if they were all spelled-out. But I'd like to avoid supporting both abbreviations and the complete spelling. Every additional test that (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
     
          Re: Interpreting the proposed FACE meta-command —Steve Bliss
      (...) Recognizing multiple forms of the command shouldn't add much to rendering. Each file can be parsed once, and then the post-parsing results cached, for later re-reference. The FACE meta-command would be stored as an opcode and a single (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Interpreting the proposed FACE meta-command —Steve Bliss
     (...) Why not recognize it all ways: 0 FACE ACW 0 FACE ANTICLOCKWISE 0 FACE CCW 0 FACE CLOCKWISE 0 FACE COUNTERCLOCKWISE 0 FACE CW 0 FACE DOUBLESIDED 0 FACE DS 0 FACE UNKNOWN This adds a bit to the parser, but not so much. The recommended standard (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
    
         Re: Interpreting the proposed FACE meta-command —Gary Williams
      Steve Bliss wrote in message <37f8c4a9.238320530@...et.com>... (...) Well, I have nothing against anticlockwise, but it's redundant. Seeing ACW where one expects CW or CCW may confuse some people. I checked the dictionary because I honestly didn't (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
   
        Re: Hidden surface removal, and vertex order in part/primitive DAT files —Steve Bliss
   (...) No (like Gary said). Two reasons: 1. The 0 FACE directive would be an operative switch, not a global setting. This is convenient, but it is also necessary in some cases. Most importantly, it would allow the 0 FACE meta-statement to appear (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
 

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