Dennis Pierce (dpierce++at++dolphin.orlando.sgi.com)
Wed, 18 Sep 1996 09:49:06 -0400
No method is "silly" if it works, and from your post, it seems that your
method is fine. However, there are a couple of issues that you may have
met or may soon meet, so it is worth spending a few moments reviewing the
overall approach.
If you're simply in the "flying logo" domain, inventor is great because
you can use a text editor to add texture and tweek the model. Its
relatively simple to create models with AutoCAD, texture them by editing
the ASCII .iv file, and load each model separately into a hacked perfly
attaching a DCS to the top of each model. With appropriate code development,
you can extend this to add GUI controls for splines and special effects.
Inventor is also the basis of the Cartoon Network's Moxy Moto, so it is
quite useful for handling real-time effects, if the models don't get too
large.
On the other hand, if you are truly going to have "terrain" that you
wish to fly over or drive through, you may find inventor to be somewhat
cumbersom. Again, the basic modeling is simple, but the run time (and
real-time) performance may fail to satisfy TV standards. And this is
where this whole discussion falls into the purely subjective realm.
Objectively, however, OnyxRE/Performer displays about 7K-9K well behaved
polygons at 30 fps. So, the 7K is a good target number. Of these,
a typical mix would be 1/3 for the terrain, 1/3 for the models, and
1/3 for "other" things (buildings, trees, ...). This allocation comes
from a general simulation for training rule-of-thumb, and may have little
bearing on your task. But it is a place to start. Now, if you use
2K polys for the ground and have just a little bit of ground to cover,
its quite possible that you can make a great looking scene. On the
other hand, if you're trying to make a general area that may be viewed
from any arbitrary angle or may cover quite a bit of "real Earth", you
will need many more polygons for representation. In this case, you
will not want to try to display all of the polygons at once, but do
something called level-of-detail (LOD) management, whereby the near
ground is represented in detail and the far ground is quite coarse.
I'm sure you've seen the LOD controls with perfly, but without a modeler
that allows you to build separate LOD's and a loader that puts in the
separate models with suitable switch distances, its not possible to
access the feature. What you're looking for, then, is a modeler with
a supported IRIS Performer loader that will allow you to build multiple
LOD's for your terrain, load these LOD's, and display the correct one
during run time. The modeler that I'm familiar with is MultiGen using the
DTED option. Its pricey but highly worth it, especially if you want to
do things like fly through the Grand Canyon or dance on the plains of Mars.
(MultiGen is in San Jose, CA).
Finally, there is a new feature from MultiGen called continuous adaptive
terrain (CAT). This is an example of the Holy Grail of terrain handling
because it eliminates the need to fiddle with the data. Well, there is
some initial processing, but you don't need to build multiple LOD's of
the area in question since the algorithm performs a seemless blend between
a <determined_by_the_algorithm> number of levels. Actually, the algorithm
performs a continuous run time grouping and splitting of polys based on
things like how much a feature changes and how far away you are viewing
the feature. Check with your local SGI office to see if they have a
demo CD of CAT.
Good Luck!
On Sep 18, 0:37, Nuno Godinho wrote:
> Subject: Re: .ptu data files available to download?
>
> > We do not have the "ONYX Greatest Hits" cd and am wondering if
> anyone
> > knows where I can download a .ptu data file? I have a terrain post file
> and
> > want to drape a raster image over the top. I intend on reformatting
> these 2
> > data files into the .ptu format. PTU appears to be the simplest
> solution,
> > maybe not;)
> >
>
>
> Hello.
>
> I'm creating 3d computer generated advertising videos using Performer on
> an Onyx and I'm really interested in this .ptu data format. Actually I
> still didn't understand it's advantages. Can you explain me how to create
> them and how can it be used?
>
> I'm currently using VistaPro for PC to create 3D terrains from .PCX color
> maps. VistaPro generates .DXF which I finally convert to .IV. I then apply
> a texture to them using ShowCase and voila'.
>
> Is this a silly method?
>
> Actually we got Alias|Wavefront last week but I still don't know how to
> use it.
>
>
> Can you please point me to all the information about these matters?!
>
>
> thanks
> Nuno
>
> PS. Oh, and how can we get ONYX Greatest Hits?
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>-- End of excerpt from Nuno Godinho
---- Dennis Pierce SGI / Ste 130 / 900 Winderley PL / Maitland FL 32751work : 407.660.0073 vmail: 800.326.1020 x58548 ======================================================================= List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/ Submissions: info-performer++at++sgi.com Admin. requests: info-performer-request++at++sgi.com
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