Subject:
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Re: Quick Parts Authoring Questions
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sat, 17 Nov 2001 16:51:54 GMT
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Viewed:
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684 times
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In lugnet.cad.dev, Richard Marchetti writes:
> Hey Y'all:
>
> It seems to me that a lot of you work through a lot of stuff on paper first,
> given that I wondered what sort of tools you might use.
Necessary for all except the simplest parts.
>
> 1. Do you use isometric grid paper (if it exists...)?
No just squared paper. I find metric 2mm/10mm/20mm very useful, usually scaling
at 4mm=1LDraw unit. Not sure how widely available this is in the US, but there
must be an imperial equivalent.
>
> 2. Do you use tools like calipers, what have you (how do you physically
> measure the inside of a part)?
I use a micrometer for outer dimensions, but more important is to measure a
part against other known parts.
>
> 3. When authoring a part, what is the relationship of the element to the
> origin of the coordinate system? Is the origin supposed to be the X,Y,Z
> center of the element?
Depends very much on the part, but usually to make it convenient to orientate
it with other parts. Orientation should be consistent with other analogous
parts.
>
> 4. Obviously using primitives is similar to reusing blocks of code, but
> clearly one does not have to do so. Should one use primitives? Why?
a) because its a lot easier, once you get to know how to use the primitives
b) to keep the size of the part file down
c) to allow primitive substitution in renderers which can display truly curved
surfaces
Primitives are really for highly reused structural features - a repeated
feature specific to only (or few) parts may be defined as a subfile - stored in
parts\s and referenced like s\xxxxxxx.dat, and named like NNNNsNN.dat. Subfiles
are also commonly used for decorated parts to store the code for the
undecorated surfaces in a single location.
> 5. I wasn't clear on the notation for slicing a primitive at an angle (if
> say I didn't want the upper portion of an interior tube, or cylinder, to
> continue through a plane representing a surface slope) -- is there special
> notation for that?
The *cyls and *cyls2 primitives provide for that.
>
> 6. When I place a primitive in my dat file, is it automatically oriented in
> a certain position (probably not)? How does one orient the primitive in the
> dat file, what is the notation?
All primitives do have a default orientation - see
http://www.ldraw.org/memorial/archive/FAQ/Primitives_Reference
There should be a later version on ldraw.org somewhere, but not obviously
accessible (help, please, Tim Courtney)
>
> 7. Is it always the case that the wireframe is the graphic representation of
> the "Type 2 Edge Lines? Are there exceptions?
Only exception I can think of is the use of type 2 line in patterns to ensure
they dont disappear at low-mag. Generally, yes type 2 lines represent the
wireframe, although for curved surfaces type 5 lines help the visualisation.
>
> 8. Can anyone recommend any superior resources for Three-Dimensional
> Geometry or Coordinate Systems, etc. either online or as a book? Is that
> overstressing the issue (I can see where the main point is to merely map the
> points of a part)?
>
> I apologize if some of these questions seem quite elementary to you people,
> it's been forever since I took ANY kind of geometry (18 years or so).
>
> Thanks in advance,
>
> -- Hop-Frog
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Message is in Reply To:
 | | Quick Parts Authoring Questions
|
| Hey Y'all: It seems to me that a lot of you work through a lot of stuff on paper first, given that I wondered what sort of tools you might use. 1. Do you use isometric grid paper (if it exists...)? 2. Do you use tools like calipers, what have you (...) (23 years ago, 17-Nov-01, to lugnet.cad.dev)
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