how are you changing the topology in 3d max without altering the vertex order? i don think you can ,can you? because you would have to mess around with the vertices to create quads? i really don think it is because you have triangles as my model unfortunately has a few triangles on the ear (tricky thing to model) and it works fine. what you could check is that you dont have any overlapping or inverted areas on your uvs, i dont know if it has that effect but i know the tutorial i was watching said you will have a lot of problems if you have them and you want to take your work into zbrush. im only new to zbrush but id say check that first as its an easy thing to fix to test.
Thanks to everyone who did the heavy lifting on this one already! 
I will be importing my new uvws from max tonight and this info will undoubtedly save me loads of
trouble. Thanks again to all involved!
I sculpted the initial shape from a PolySphere, and then did the topology in ZBrush, then sculpted the higher details. I then exported the lowest level, and followed the instructions for importing/exporting for max.
If I would have used max for the topology I would have had way worse results than just a single area messing up. Again, the only thing about the area exploding is that there’s a triangle there. Can’t say this is positively the reason for the problem, but it’s the only thing that is different about this area on the model.
What I don’t get is why the morph target is not working with it since that’s supposed to take UV’s only, and not the geometry. And there’s no overlapping or messed up UV’s. I’ll try to get a snapshot of what I’m talking about later.
I was having the same eploding issue with Hexagon for creating new UVs on my Zbrush model. It was reordering everything, so after importing and trying higher subdivisions, it exploded.
My method is pretty simple and worked twice for a simple shape made with 3 zspheres and high poly detail applied. Don’t know if this will work for any application or has draw backs.
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I export the lowest subd from Zbrush, it has no UVs at all, no polygroups either.
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Import it into Hexagaon with default settings if I recall. Create the UV map. Export it as object file (again, this file is bad as it will explode).
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Open UVMapper. Load the original untouched Zbrush Object. Import UVs from the bad Hexagon object file. Save it as a new object.
That was it, instead of using the bad hexagon file, I used UVMapper to transfer the UVs to the Zbrush object file. So importing it back into Zbrush it doesn’t explode, and the new UVs work perfectly.
Here’s the simple test I did, rendered in Carrara with the 2048*2048 displacement map I was finally able to make, subdivided 6 times at render. Includes zbrush image, lowest polygons in Carrara, and final render:
http://other.toonguru.com/3D/displace_test.jpg
I finally feel like I’m getting somewhere with these programs working together.
Now comes tougher part, maybe my method won’t work with a more complicated UV map compared to this simple shape I did. Anyone know any drawbacks by doing it this way?
wish my programs would work right
I just came across the very same ‘exploding re-import’ problem; the solution was to export the mesh WITH UVs from zbrush. So I had to create some default GUV/AUV or whatever, and check ON the ‘Txr’ switch under Tool>Export.
You may not leave the UVs blank when exporting, that’s the deal. I guess. 
Hey guys, I got a question…(I am using ZBrush 3.1 and Max 8). I followed the aforementined steps for importing new UVs and worked fine the first try. Nice. Now, while working on the model with new UVs (7 subdivisions, system w/ 4Gb of RAM & dual processors), ZBrush crashes once every half hour or so for appearently no reason. Just closes. I’ve been working on this model for quite sometime, and I’ve had alot of crashing issues already, but they were usually always when saving or working on the highest subdivision level. These new crashes are just random and frequent. I’m guessing it might have something to do with the new UVs. Anybody else have an excessive crashing while working on a model with new Uvs issue? Is there any sort of way to “clean the history” of the model? Just wondering…
thank you all i had this problem and not it’s fixed.
holy mother of the zbrush gods thank you!!! i’ve been trying to figure out why i couldnt get displacements working in maya for weeks! go figure the problem was importing under best guess >.<. Had i of spent any longer on figuring this out i can only imagin how many years i woulda shaved off my life lol!
Thanks again bud!!! 
haha, I’m glad the post helped out alot of people.
Yeah… thsoe little things can really effect the entire work…
=)
Thankyou! Thankyou! Thankyou!
Oh man, I’ve been banging my head against this for days, and being a beginner I really had no idea where to turn. You just saved me, my friend.
I tried your solution but it doesnt work for me. I think I had the settings wrong when I exported but its too late to fix because I spent the better part of a day unwrapping it. So I can either unwrap again or just resculpt.
is there a way to use the projection feature from topolize to project the higher levels onto my mapped tool? they are exactly the same at lvl 1.?
I’m not totally sure I understand your question, but if your asking what I think, here’s a possible answer…
If your reimporting your newly UVd mesh into ZBrush and it’s not cooperating, then in your 3D app that you did your UVs in, try tranfering your UVs to another properly exported from ZBrush mesh…
Another option could be the “Project All” feature in the Subtool pallette. Take your original detailed, non UVd ZBrush tool and append your newly UVd .obj/tool to it. Subdivide the new UVd mesh up to the level of your original non UVd mesh, and with it selected, the original Subtool displayed, and other subtools turned off, hit “Project All”. That should project the detail from your original to the new mesh pretty well, assuming poly counts are similiar. There may be some topology issues depending on how complicated your original mesh is…In that case, drop down a couple SubD levels (about in the middle, say SubD level 3) and press “ReProject Higher Subdivision Levels” in the Geometry pallette. (It’s probably a good idea to do this no matter what) That will help more evenly redistribute the polys on your new UVd model. If there are still topoology issues, smooth them out as best you can, and repeat the process. You shouldn’t have to redo your UVs. Seems like there’s always a workaround…Lemme know how it goes.
thanks but i ended up just resculpting the higher levels. i used a morph target so it didnt smooth when i divided the mesh it worked out pretty well. thanks again.
Just to say a massive thank you to MATT_KB (and everyone else who helped in him creating that list of pointers).
I’ve been suffering with this problem all day and had tried every method I could come accross to fix it. Nothing had worked until I read this.
Great work
This is my exact problem, thanks for the insight it is helping a bit, the whole exporting three times and mrg/grd business. The outcome is producing a couple problems though, hopefully someone will have a clue as to what is wrong.
So, I was getting the exploding mesh thing, until I used with tut (yay), now I have done it it does let me bring in the mesh at the old mesh’s lowest subdivision level and go through the higher subdivisions without exploding; but the first problem is the mesh is now off centre and shrunken [ probably not the hugest problem, could resize and move]
and the main problem, although the UVW map firs the shape of the one I did, all the polygons are mixed up in terms of which polygon on the map represents which polygon on the 3d model
using 3ds max 2009 and zbrush, but ive tried it with 3ds max 9 too
any insights would be appreciated, the stuff ive found in this thread has already been very helpful too so thanks again
edit; I’m looking into it right now top priority, so hopefully I should arrive at an answer eventually =p if I find anything I’ll be sure to post it up jsut incase someoens in the same boat
digiegg, thanks for starting this thread (a while back it seems)-- followed your instructions (along with DemonFrost) and the exploding stopped!
Ok, now i am having the same issues with exploding meshes and I am using XSI as my initial modeller. Now when I go in to import my OBJs with the new uvs, everything goes haywire…
Does anyone have a solution for this? and I did use the FBX comverter and everything still explodes and it is starting to piss me off…
Fixing Exploded Meshes in Zbrush (For those using XSI)
Hey I have come up with a new little fix that seems to work for me when updating my UVs and keeps the model from exploding, which does piss me off when I want some new UVs.
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Export the old OBJs from ZB, but turn off MRG in the export options first. Use Subtool master to export all of the objs at once at lvl 1 subd.
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Import all of the old objs into XSI and delete the “Samples” cluster. It will also help if you have the same obj with the new uvs in the scene.
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Now, go to model>property>GATOR. It will ask you to pick the target. The target will usually be “ZbrushPolymesh3D” (when you import from ZB it will be called this), pick that. Then the source will be the model with the new UVs you want. Right click to end the session. In the ppg, you want to transfer the UV, so hit “Transfer”. And change the transfer option to Closest Vertex. This prevents GATOR from welding points at the borders. And also click on the hide button and check out your new model.
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Now just export the “ZbrushPolymesh3D” as an obj at the default…
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Back in zbrush, select the object that you want to update the uvs to. Import the obj you just saved and voila…your model has the new UVS. and if you go through your subd levels without exploding, you did it!
i hope this helps.
and special thanks to Goast666 for the help
Thanks so much for those who are taking the time to help with ZBrushes convoluted technical weirdness! Yay you!
Tom