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Subject: 
Re: Crazy, OK Heretical Idea ...
Newsgroups: 
lugnet.cad
Date: 
Thu, 1 May 2003 15:52:52 GMT
Viewed: 
684 times
  
In lugnet.cad, Kyle McDonald wrote:

Polygons, could be flagged as belonging to the front, back,
top, bottom, left, right, (or always drawn) of a brick, so
that a render could easily know which polygons to leave out
when another brick was placed on top or next to this one.

I'm not sure the top/bottom/left/right would work in part files - since
parts can be rotated to any orientation.  If you mount a plate on the
side of a headlight brick, the 'top' of the plate is no longer the top.

LDraw does have one type of LOD built-in to the base language: stud
detail.  A regular stud in LDraw has 32 polygons.  Open studs (like
Technic studs) have 48 polygons.  A 2x4 brick sports 11 studs,
contributing 400 polygons toward the brick total of 414 polygons.  So
simplifying studs can contribute heavily toward speeding up rendering.
:)

Here's how it works:  All p-files with names like stud*.dat are assumed
to follow the 'stud rules'.  Basically, each stud file is implemented as
being 4 LDU tall, with the base at Y=0, and the top at Y=-4.  Each file
has a simpler (fewer polygons) version named stu2*.dat (so stud.dat has
a matching stu2.dat, stud2.dat has stu22.dat, etc).  There's also a
single file, studline.dat, that implements a stud as a single line.
LDraw has a 'fastdraw' option, that uses the reduced-polygon version of
the studs.  LEdit has a 'studs-as-lines' option, to render studline.dat
in place of any stud*.dat file.  MLCAD also has options to use any of
the LOSD options.

Steve



Message is in Reply To:
  Re: Crazy, OK Heretical Idea ...
 
(...) Yes! LOD would be very useful. There are several general purpose LOD methods out there, but again we may be able to improve performance or ease a renderer's job, by supplying even more information in a part file. Polygons, could be flagged as (...) (21 years ago, 1-May-03, to lugnet.cad)

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