Subject:
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Re: Thoughts on File Format for LDraw Animation
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Newsgroups:
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lugnet.cad.dev
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Date:
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Wed, 26 Oct 2005 22:52:12 GMT
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Viewed:
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2628 times
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In lugnet.cad.dev, Anders Isaksson wrote:
> Kevin L. Clague wrote:
>
> > MPD does not help this in any way, because again, there is only part
> > type (file name) and no instance name.
>
> But as I said, if you put all instances, that need to be named, in a subfile
> of its own you *have* named instances. It wouldn't be too difficult to write
> a helper program (or add-on) that does this folding for you (creating a
> subfile of selected parts inside an MPD).
>
> > LDraw has no support for the naming of instances part usages.
>
> Objection. The MPD format gives one way of doing it.
Ha, ha, ha.... I had this long winded response argument all typed out, and then
Mozilla died. Probably divine intervention. Let me try and see if I can get
this one out with less energy.
According to this specification:
http://www.ldraw.org/modules.php?op=modload&name=News&file=article&sid=47
MPD provides two language extensions:
0 FILE <model>
and
0 NOFILE
<model> is the file name of the file if it were extracted from he MPD archive.
There is only one more piece of information that MPD provides:
The first file in the archive is the top level model.
Nowhere in the MPD specification is hieriarchy communicated, except for the
minor case of what the top level model naem is.
From the top level file all hierarchy is specified by LDraw 1.0.0 type 1 lines.
MPD is irrelevent in this discussion.
>
> > I can think of a number of places where instance names would be a
> > great help.
>
> Sure. It's necessary for animation, but I don't think the LDRAW format
> should be used for instrumenting the animation itself. LDRAW is a format for
> describing static models. Period.
LDraw 1.0.0 already specifies time, by order that parts are added to the file,
and quantized into time units called steps, using the STEP meta-command. MLCad
also provides special variants to STEP using ROTSTEP. This way of specifying
time is great for building instructions, but is not the way to go with
animation.
My point is that LDraw files, from their inception by James, are not just static
models. They have the element of time.
>
> To give life to those static models we need more.
>
> MPD gives us a tool for creating a hierarchical model inside the existing
> LDRAW specifications, now 'all' we need is another program which can read
> such models, let us specify time line(s) for movable parts, models, scenes
> or a whole movie and send the result into POVRay (or Blender or whatever).
I agree that you *can* overload file name to mean instance name, but that has
nothing to do with MPD.
Furthermore I think that named part instances could be quite handy for building
instructions. I can list my reasons if you'd like. I added REMOVE_GROUP
meta-command to LPub so that groups of parts could be removed from the model by
name. I've done so without overloading any names.
> I don't see any big logical obstacles in that route, only hard work creating
> the program, and of course, first creating the specification for that
> program...
I don't either, nor have I said it wouldn't work.
I also don't see why you couldn't use groups to rename part or parts.
I just don't think it is the best solution. I see a possible solution that
could help animation, *and* building instructions: named part instances. Can
you see my point?
Kev
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Message has 3 Replies:
 | | Re: Thoughts on File Format for LDraw Animation
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| (...) That's correct, but irrelevant. The hieriarchy is communicated with one single MPD in a way that would be impossible using one single DAT/LDR - if you put it together correctly, of course. (...) I have never used LPub so I'm not familiar with (...) (19 years ago, 27-Oct-05, to lugnet.cad.dev)
| | | Re: Thoughts on File Format for LDraw Animation [DAT]
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| (...) Um, I'm not sure this has been worked out... I think James was saying that the subfiles in an MPD can be treated as the 'name'. This is true, as long as you also require that each subfile only be used once. So a file like: 0 FILE test1.mpd 1 (...) (19 years ago, 27-Oct-05, to lugnet.cad.dev)
| | | Re: Thoughts on File Format for LDraw Animation
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| (...) Yes, but you can give the 'files' any name you want inside the MPD. They don't *have* to match the part name outside of the MPD. So you *can* get named parts inside an MPD (with the help of a suitable 'post-processing' program). I certainly (...) (19 years ago, 27-Oct-05, to lugnet.cad.dev)
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Message is in Reply To:
| | Re: Thoughts on File Format for LDraw Animation
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| (...) But as I said, if you put all instances, that need to be named, in a subfile of its own you *have* named instances. It wouldn't be too difficult to write a helper program (or add-on) that does this folding for you (creating a subfile of (...) (19 years ago, 26-Oct-05, to lugnet.cad.dev)
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