CGTalk - a weird obj thing

blinky

04-20-2006, 09:31 AM

I ve been learning xsi and made a head. Took it into zbrush for detailing and texturing no problems there. Well im texturing round the eyes and i think hmm a few tweaks on the uvw's will help here. So i export it as an obj ( lvl 1 cage ).

However we had a problem here with our xsi licences yesterday afternoon so i just popped it into max to make the adjustments and exported it back. I have the tool on level 1 and import the new obj ( as i ve done many times before ) it works fine. However when i pop up a sub div the whole mesh shatters.. polys all going off ranomly. Not good. I make a few tests, i tried welding the uv's in max ( no joy ) i even tried simply importing and exporting from max without doing anything. Still no joy.

So this morning ( liscence problem sorted ) i do the same in XSI - works perfectly. pops up and down the sub divs with no errors.

SO

why?

Is an obj not just an obj?

TVeyes

04-20-2006, 07:43 PM

Hi,

Yes an .obj should just be an .obj, in a perfect world of course:) Unfortunately different programs import and export .obj's differently. For example, one program might recognise the .obj Group definition as a polygon selection set or polygon part while another program sees them as different objects.

So while practically every major program supports the .obj format they accomodate that format to how the program in question works generally. Luckily there are usually various settings you can apply to import and export ZBrush friendly .objs.

When you used 3DSmax for your tweaking the vertice order was changed, that will result in garbled geometry in upper subdivision levels.

For 3DSmax there are some settings you should use and stick to, regarding the .obj format. Use >>these settings<< (http://206.145.80.239/zbc/showthread.php?t=17027) for both import and export, I am not sure of the need for the ZBrush settings.

blinky

04-21-2006, 07:12 PM

Its a strange one. Its not a problem now as i re did the uv's in XSI anyway, but its odd that zbrush accepted the low cage changes perfectly but got messed up when i went up the subdiv's. Had it given the usual "bah this isnt the correct mesh n00b," warning when i tried importing the changed mesh i wouldnt have given it a second thought.

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04-21-2006, 07:12 PM

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