Importing - Strata Units


Here's a secret you may have missed: Strata's internal unit is the point,
which is 1/72 of an inch. This comes from Strata's historical tie-in to
desktop publishing applications, specifically Illustrator.



In either Strata or Illustrator, if you make a rectangle which is 10" x 5 "
the application is actually handling the object at 720 x 360 units. Since
Illustrator and Strata use the same secret hidden mystery unit, importing an
Illustrator file into Strata yields expected results, so we have gotten by
for many years without actually needing to know this vital secret unit
information.

As Strata becomes more and more capable of interacting with other 3d apps,
knowing this fact becomes more useful, if not necessary, to know. (it is
also useful to necessary with the skeleton system, but I'll leave that to
someone else to explain.)

Other applications do their own unique units thing, too, so to trade meshes
successfully with various apps, you need to know their secret units, or have
a decoder ring for fingering it out.

Example: Silo to Strata, OBJ

Silo's default internal unit is the meter, but for reasons unknown to me,
Silo also has a default unit factor of .5. If you leave your units just like
this in Silo, and ignore the fact that silo is labeling the units as
meters,everything will be fine, nobody will get hurt.

Don't try to change the scale factor to 1, which would seem the normal thing
to do: it will mess you up if you want consistent units from Silo to Strata.
(This scale factor is important if you want to write STL files for rapid
prototyping, though.. But that is yet another topic.)

So (as long as you leave the silo default scale setting to .5)

1 Silo meter = 1 Strata point.

That's right, a meter and a point are the same thing, at least when trading
files between Silo and Strata, because we aren't really dealing in real
world units, we are really dealing with the two applications' default
internal units.

So, if you build a box in Silo that is 10 meters by 5 meters by 2 meters, it
will import into Strata at 10 points by 5 points by 2 points. Hmm.

That's what the secret decoder ring on Strata's new OBJ importer is telling
you, when you import an OBJ from Silo: It tells you your 10 x 5 x 2 meter
object is 10 x 5 x 2, but is doesn't tell you once open in Strata, it will
be 10 x 5 x 2 "points* !!

So, now that you know Strata's internal unit is the point, you know to
multiply your 10 x 5 x 2 object by a scale factor of 72 at import to get it
to be 10 x 5 x 2 inches, right?

And if you really want your 10 x 5 x 2 meter silo box to be 10 x 5 x 2
meters in Strata, well, you need to know this conversion:.

1 meter = 2,834.645669291points.

So, when you import your Silo OBJ, enter 2834.64567 in the scale box on
import into Strata. You should get a box at the expected size in meters in a
Strata file which uses meters for units.

Pretty much the same thing holds for Wings, except Wings didn't label its
units at all last I checked, and Wings doesn't have the mystery scale factor
to worry about..

One more thing: Strata's old triangle mesh, from version 4 and earlier,
didn't have a high enough level of precision to actually work in points: a
10 x 5 x 2 mesh old render poorly, a 100 50 x 20 mesh with any level of
detail probably would have bad triangles, too.

Strata's new mesh is much more precise, so if you want to work in points, to
cut out all the translation, Strata can now render these smaller meshes
well.

As always, your mileage may vary, so DO try this at home to see how it works
on your projects, before getting in over your head on a real paying job.

And remember, every application will have its own internal units, you need
to get to know the internal units of all the applications you use to get the
best results when trading meshes.

--
Jean

Posted: Mon - June 12, 2006 at 02:57 PM          

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