ZBrushCentral

Offset/translation on import issue

ZBrush Usage Questions
#1

Ok, starting with the nice part: yes, I love ZB3.1. In so many ways, it totally rules and I’m very happy, except…

…there still seems to be an issue with an obj that has been imported and altered in Zbrush becoming offset by a miniscule amount upon export. Now, if you’re working at the larger scales of apps such as is normal in Max and Maya, this tiny amount may not be a noticeable problem, however our studio turns out volumes upon volumes of Poser content in which this offset issue is a HUGE problem. Granted, there are workarounds, but a straightforward fix for this would be nice. Specifically what’s happening is this:

We do all our modeling/uv dev inside Maya, albeit at “poser” scale. We have typically done the majority of our morph targets using Zbrush 2.5 and recently upgraded to 3 then 3.1 where this issue came about. Once a mesh is completed, we’ll export, for instance, the head, import into Zbrush and sculpt out the morph. That is then exported and imported into Maya where it is applied to the original as a blendshape so that we may check it before proceeding to Poser. Once the sculpt has been imported to Maya, however, we can see a very slight but visible offset on the Y axis. Now, I know there are a number of workarounds for this, which we put to use currently, however I’m wondering if we need to be resigned to a workflow of these workarounds and just remain prepared for this issue with every piece we develope, or is there something in the works to fix it, or even the possibility that we could just be missing some little option somewhere in the import/export from Zbrush.

I know problems similar to this have been posted elsewhere but after reading and reading through the forums here, I admit to experiencing a bit of “forum fatigue” in searching for a straight “yes or no”/“do this or do that” answer.

Thanks in advance for any assistance!

Les

#2

Could you provide a breakdown of the exact steps/buttons clicked that you’re using in the various apps, including any import/export settings? I’m just talking about the steps relating to import and export – not anything with the sculpting process itself. :wink:

Also, are you at any point using the Offset or Unify deformation, modifying the position of the crosshair in the Tool>Preview, or using the S.Pivot feature?

#3

You can try this plugin by marcus:

http://www.zbrushcentral.com/zbc/showthread.php?t=49815

Which works but is slow because of the limits of scripting. Or scale up the mesh before importing into ZB.

@aurick : This is the illustration of the problem:

http://www.zbrushcentral.com/zbc/showpost.php?p=382852&postcount=14

And i will again state that this is a serious issue that can have all sorts of nasty side effects in any app, not just poser. Poser just has the most obvious problem with it.

#4

Nope: not using anything in the Preview or S.Pivot, nor any kind of offset deformations either.

ZBrush ImportExport under Preferences has the following checked: iFlipY, iFlipZ, eFlipY, eFlipZ, and Import Polygroups.

In the Tool menu, the Export settings have the following checked: Obj, Qud, Txr, Grp, with Scale at 1

The import into Maya has Create Groups set to False, the same setting that I’ve been using in there successfully for years to bring morphs in that were done in previous versions of Zbrush.

BTW: will be checking out the other suggestions mentioned in this thread so far.

Thanks!

#5

ghonma-- thanks for the headsup on that script. It is definitely slow, but at least it works. The slowdown of the script is not as bad as the workarounds so I’ll be making use of that until a better fix becomes available.

#6

Hey guys, didn’t want to create a new thread about this issue so I’m bringing this one back after Searching on this subject… my problem seems vaguely related to this, since it involves OBJ imports getting wildly different scales/offsets when imported.

I’ve got a .ZTL with 4 SubTools, and I wanted to Append a mesh I made in 3DS Max, so I exported the main SubTool as .OBJ (with an Export Scale of 1 in ZBrush, and eSwitchYZ enabled). This model is loaded into Max (default .OBJ importer, vertex scale of 1.0) with no problems and used as a scale reference for some accessories I’ve modelled.
So I export the accessories from Max and want to append them to my main .ZTL file, but when I imported the .OBJ (with iSwitchYZ enabled to match the export), it is about 5 times as big as it should be, and far too high above it’s intended location.

So as a test, I tried these steps, and this is where the weirdness begins…

  1. Get my .ZTL file with 4 SubTools selected and in Edit mode.
  2. Choose one of the SubTools to Export. The Tool’s Export Scale is set to “1”.
  3. Save the SubTool as an OBJ in an arbitrary location.
  4. Immediately Import the OBJ back into the selected SubTool. What I would expect is for the mesh to be in exactly the same position and scale, does that seem reasonable?
  5. Evidently not… the mesh is about 5 times smaller than it used to be, and twice as high up. Bear in mind that this OBJ was not touched by any other package, it was simply exported and re-imported from ZBrush back into ZBrush.

It seems like a glaring oversight that meshes would not retain their correct relative scale and positioning when imported and exported - certainly it makes it very hard to match up pieces modelled in a 3D package and Appended as SubTools after the fact.

Is there anything obvious that I’m doing wrong? I’m sure it shouldn’t be this complex, it should just be a matter of Export and Import…

Any help would be greatly appreciated.
Cheers,
-MoP

#7

Hmm, after a bit more searching and reading, I think Pandaren hit on the issue here, in his last post:
http://www.zbrushcentral.com/zbc/showthread.php?t=50843&highlight=import+scale

Basically it looks like ZBrush 3.1 is doing a “Unify” operation on any meshes that are imported, so everything gets scaled to the same bounds… which seems quite unnecessary and indeed I think is detrimental to most workflows!

Is there any way to stop it doing this Unify operation on imported meshes? I can’t find any options which suggest that in either the Tool or Preferences menus :frowning:

#8

Just wanted to back up this thread by adding that this obj import resize/offset issue is making the retopology workflow in ZB3 a nightmare. This is why I was so disappointed that there was no true 3d viewport introduced in V3 and this whole ‘Perspective view’ is but a mere fudge to please the masses temporarily.

I have a lowpoly mesh that I retopologised using the hipoly mesh as reference in Silo. Imported these into Zbrush 3.1. Then used the hipoly in the Rigging slot, and lowpoly retop mesh in the Topology slot. Edit Topology reveals that the lowpoly mesh is now misaligned with the hipoly mesh thus creating an incorrectly projected adaptive mesh. Very frustrating.

If it were a personal project I could find a workaround for this and get by, but in a Work environment this is time&money lost on something that should just work… There is no problem with this in Mudbox where what you see in the viewport is exactly what you get in Xsi/Maya/Silo etc. but unfortunately Mudbox doesn’t have the breadth of tools available. At least it is a solid app.

I am venting this frustration at Pixologic. Do they read or care about these posts? who knows… but you can only try.

#9

Two solutions that I can think of:

  1. Apply Tool>Deformation>Unify to both models.

  2. Export both models from your other app as a single OBJ with them already aligned. In ZBrush, clone the model and then split it into the two separate objects.

#10

Thanks for the suggestions Aurick.

Unfortunately, the first solution won’t work in the majority of cases I can think of, since (as far as I’m aware), “Unify” works based on the bounds of an object, so if they’re different, they won’t be aligned/scaled correctly.

This will also not work in the cases of wanting to import a modelled piece from an external 3D application since again the bounds will be completely different (for example modelling a helmet in 3dsmax to import on top of a ZB-sculpted head).

The other solution sounds much more feasible, but again is far from ideal.
It will also fall foul of importing more objects at a later date - since it “Unifies” them independently as they are imported, every time you wanted to add a mesh you would have to export the ZB meshes and reimport them all with your new piece included.

I will try out some of these ideas when I get home tonight and let you know how I get on. The 2nd solution sounds like it could work fairly well for the stuff I’m doing now.

#11

Hi All! i’ll have to add another funky effect of this scaling issue we have here, thought i wouldn’'t start a new thread…
So here i go: been conccepting a charcter in 3d before retopo , sonow that im at a point where it can be retopologised and rigged in maya, we needed to rescale the character (much bigger,as we have to work with a biggger scale in maya from now on for our new pipeline)…updated the level1 in maya to proper scale and new bind pose, imported back at level one in Zb3.1…everything is fine so far, but when i dubdivide, to my biggest surprise, most of the detailed sculpted got smoothed a lot!
Only way to get passed it is to scale using the highrez level of the model! and as you can imagine, not possible in maya, and very,very unpractical in Zbrush!
Anybody know a solution for that?
thanks
abe