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View Full Version : What is a 'Model Unit' in LW?



JBT27
09-16-2008, 03:49 PM
This kind of comes off another thread where I was asking about interactive 3D models online.

I've started using the trial of Adobe Acrobat 9 Pro Extended, but have had some frustration pinning down the right scale so that LW imports measure correctly.

Acrobat uses this thing of 'model units' for the user to set how many of those equal whatever actual measure you need.

I am assuming it is consistent with any model exported out of LW, in any format it can. I have been testing with a 1m cube, which appears to have 100 units to 1m in Acrobat, or obviously I can set 1 model unit to 1cm, and so on. But that's kind of arbitrary, so it seems to me, though again it would seem that my 1m cube, according to Acrobat, has 100 model units on an edge.....

I'm just a bit confused and worried about this, because these online models are going to be used by architects and demolition people to assess scaffolding and such, so I need to be absolutely sure what's going on :D

Would appreciate any help.

Thanks.

Julian.

Giacomo99
09-16-2008, 05:28 PM
I'm not sure what's at issue here---can you export a model from Acrobat and see how it's transformed in Lightwave? That would seem to be the easiest solution.

JBT27
09-17-2008, 05:52 AM
I suppose the core of this problem is about how Acrobat sees the scale of a LW model - it uses something called 'model units', and I wondered if LW had some internal arbitrary unit that it uses to determine scale.....hmmm.....now I'm confused.

Anyhoo.....it's looking like the real culprit is models exported out of 9.5.....they just don't work so well in Acrobat currently. Exporting the same out of 9.3.1 does work.

9.5 objects (exported as OBJ or DXF) appear to break the snapping and the scaling in Acrobat.

Julian.

Lightwolf
09-17-2008, 05:59 AM
...and I wondered if LW had some internal arbitrary unit that it uses to determine scale.....hmmm.....now I'm confused.

No, 1 unit in LW is a metre. However, it may be displayed differently to the user depending on the unit settings.

Cheers,
Mike

JBT27
09-17-2008, 06:20 AM
No, 1 unit in LW is a metre. However, it may be displayed differently to the user depending on the unit settings.

Cheers,
Mike

Ah, thank you! That's what I needed to know. There's definitely problems with 9.5 geometry in Acrobat, scaling inconsistencies one model to the next, but from 9.3.1 geometry, setting 1 model unit to 1m in Acrobat works fine.

Julian.

cresshead
09-17-2008, 07:54 AM
i'd guess there will be a bug fix out soon to ammend that, plus the vertex order issues etc for 9.5 as well.