Max - OBJs and UVW editing

[AndrewDEC]

Hello all,

I have a question I'm hoping someone here will be able to answer...

I've sent an OBJ off to a third party artist to have some UV mapping and texturing work done on it and they are using Max 2012. I've already had extensive work done in other applications within the workflow using this OBJ (namely rigging and weight-mapping) so its imperative that the geometry of the OBJ not be altered in any way.

The first two attempts to have the 3rd party update the UV maps has resulted in me getting back an OBJ where the vertices count is different or the vertices order altered (negating the rigging and weight-mapping we've done already), which tells me they modified the geometry in some way during the import or while they were working on the UV mapping. They have now told me that it's not possible to import an OBJ into Max without encounter any changes to the geometry (something about the conversion from OBJ to Max). Is this accurate?

I tend to think this is not correct and if my assumption is correct what import/export settings should they be using or what other guidance can be shared that will avoid them altering the geometry while editing the UV maps? Would it be easier for them just to save the UV maps out to .uvs format and not bother saving the .max file?

The UV mapping software I'm most familiar with is capable of importing OBJs, altering UV maps, and exporting again without mucking with the geometry or vertices order. I have to imagine Max can manage this too but I don't know enough about it to say how.

Any advice will be much appreciated!

Andrew

[paulius-st]

well if you want to save you skining info just put this new unwraped obj file on top of the allready skined mesh and aply a skin wrap modifyer on this unwraped mesh. then select a skined mesh as a target mesh and then tick the arrow on selection "weight all points" and the "convert to skin". then drop all your other modifyers back to new mesh and delete the old one . fast efitient and easy.
and there is a another way - bitch slap the guy who modeled and didnt unwrap it from the start. i allways unwrap my models emediateley and allways curse people that dont do it the same way .

[poopipe]

Max has excellent obj import/export tools

make sure he uses the appropriate import/export presets and everything that goes into max will be the same when it comes out

The claim that max will always alter the mesh is simply bull****.

What other apps are involved? Maya can be tricky because its obj handling is very poor

[AndrewDEC]

Well, strike three. I'm not entirely sure what process they went through on the third attempt to provide us a reskinned mesh that had no geometry changes but what we got back as got 14 more vertices and a very minorly jumbled vertex order. Of course, any change at all from the original is enough to break our rigging.

I'm going to send the good mesh and the reskinned mesh over to another modeler who works in Max to see if they can try the Skin Wrap Modifier trick. I've been told that we might have problems using it on this model as it's got 90k+ polygons, 87 groups, and 15 materials. Any further advice on settings or options with the modifier to make this work would be much appreciated!

[poopipe]

if the meshes are the same shape with no overlapping skinwrap should do a pretty decent job.
if not, the the skin utilities weight transfer tools will get a decent start.

it sounds to me like the export and import settings are at fault. there's plenty of options in obj export that can change a mesh if they're enabled

try other formats instead of obj - fbx would be my recommendation if you're coming from Maya


what app are you exporting from ?
is the model clean in the first place?

[AndrewDEC]

After a little more trial and error I was able to determine that vert count of the newly mapped mesh, while in Max, is actually correct. It's when I run it through the OBJ exporter that it tacks on 12 additional verts, thus mucking up the order.

What I didn't notice until recently is that the export log was showing two warnings of a "rat's nest" in two of the groups. It actually says rat's nest. I also went back and tried to import and re-export the original unmapped mesh and it does the very same thing so this problem existed before the uvmapping was done.

Anyways, I tried deleting the offending groups and now the exported vert count is matching the vert count that's being listed in Max.

So, my question now is what's a rat's nest and is there a way to correct it without altering the vert order?

Oh, and the original OBJ was created in Maya.

[poopipe]

it's not a technical term I'm familiar with

I am however quite familiar with badly put together Maya models coming into max via obj.
Any number of issues can occur - largely due to Maya not automatically sorting out transforms etc. as it goes and not being too picky about what the user actually creates (having backface culling disabled by default doesn't help either IMO)
A lot of what comes out isn't valid in obj or max so the export/import process will alter the mesh so it makes sense and as a result it often creates new verts.

You could go back to the maya mesh and ensure that it's clean - ie reset/freeze transforms, run a cleanup, make sure all face normals are consistent and go over it with a fine toothed comb looking for stuff like mid edge verts and split edges. Then re-export (preferably via fbx)

alternatively - you could clean it up what you've got in max, get it UVd and then skin wrap it to your already weighted mesh

[AndrewDEC]

Yeah, that appears to be what happened. Unfortunately, going back into Maya to clean it up won't help as that, too, will alter the vert order which is what we were trying to avoid.

It just looks like we're going to be have to bite the bullet and correct the rigging and weighmapping issues that the vert alterations have created for us.

Thanks everyone for the advice and information!