Subject:
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Re: Parts editing made easy, anyone?
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sat, 29 Jan 2005 16:00:46 GMT
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Thanks for your suggestions, the message I
received is: "Yes, a good and useful translator
would be appreciated."
One brief comment on the issue of whether we
want clean, compact and well structured files
or not: of *course* we want clean files!
A typical Lego model has hundreds of pieces,
and having tens of thousands of polygons each
for those would drop the frame rate to unacceptable
levels on modern computers. Even a few years from
now it will still be a problem.
Dropping the studs and simplifying curved
primitives is a wonderful and obvious way of doing
automatic adaptive level of detail, and having true
curved primitives is really essential for high
quality rendering. We want both fast interactive
rendering and high quality off-line rendering
from the same part descriptions, that's the whole
issue as I see it.
Having looked a bit closer into the LDraw format
and the flaws of current translators, I have several
ideas on how to make an improvement over the
current situation.
Conditional line generation is not a big issue,
really, it is just a matter of using information
on smoothing groups from the modeling program to
decide where to use hard and conditional edges,
and then you need a reasonable algorithm to pick
two suitable adjacent vertices for the conditionals.
A bit finicky, but doable, no question about that.
Detecting primitives like cylinders and studs
would be a lot easier if the modeller prepared
for it, for example by creating a separate stud
object, grouping it and naming it correctly to
easily identify it as a stud in the conversion.
Same for cylinders. Primitives could even be
imported first from the LDraw database, used for
assembly where appropriate and then re-exported
with the original names and correct transformations.
If the utility was created in the form of a
plug-in for 3dsmax or something similar, lots
of extra information and functionality would be
available to do the job right. Even an external
file converter would do the job if there was
enough information on groups and object names
in the file, not just an unsorted, anonymous
list of polygons. Many older, standard CAD export
formats are inappropriate here, but most ASCII
export formats from 3D modeling software does
contain a lot of grouping and smoothing info.
The problem of converting *any* CAD file while
correctly detecting and substituting primitives
would be a complex 3D pattern-matching task on
which I'd rather not try my luck.
I think it would be better to solve the problem
at the source, i.e. the modeling, instead of
trying to fix it later by complex algorithms
that might not always work.
Rather than 3dsmax or Maya which everyone pirates,
I should perhaps look into writing a module for
some open source modeler. There are a few, and
some of them are getting really good.
But first I'll try some experiments with the
"ASE" export files from 3dsmax. I have a lot less
time to spend on this than I would like, but
I'll be sure to let you know if I come
up with anything useful.
Stefan Gustavson (stegu@itn.liu.se) #2407
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Message has 1 Reply:
Message is in Reply To:
 | | Parts editing made easy, anyone?
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| Are parts authors really using text editors to compose new parts? I find it hard to understand that a text editor is still the tool of choice for this relatively complicated modeling task. I might be wrong and could need an update on what tools (...) (20 years ago, 21-Jan-05, to lugnet.cad.dev)
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