THE TOPOLOGY OF THE MESH HAS CHANGED DURING CREATING NORMAL MAPS

Phena

Hi! I have several meshes with subdivisions and morph target and when I try to create displacement maps everything goes without any problems, but when I press to create normal, cavity or ambient occlusion maps this window "THE TOPOLOGY OF THE MESH HAS CHANGED" appears. After pressing “yes” maps files sometimes are created, sometimes not. After “no”-they don’t. From time to time after the command to create maps mesh changes name to “output” and loses its subdivs. I didn’t change topology, only replaced target mesh with same from Max but with a little bit different shape, it seems to work fine (because displacement is exported). Please help to solve this problem, I’ve got no idea why this is happening. Just started modeling not so long ago, so sorry if this is an obvious point. Also added an image with settings (used default for AO and Cavity). 

Ruz

it's because maybe you have not enabled certain things in the exporter like 'keep vertex order'  always make sure you have  exported the correct  subdivision level as well.

when posting its best to mention which software you are using too though i guessed it was zbrush

I generally use xnormal for baking anyway

Phena

Zbrush, yes. I thought about vertex order, worked with the same mesh all the time, modify it a little but did not change. Checked maps export on early versions of the doc where just started to sculpt the mesh exported from Max and the same problem still appered 

Phena

Update: maps are not created in Multi Map exporter menu, but everything worked out in Normal map menu with the same settings. I still interested why.  

pxgeek

Two quick things you can try:
A: delete your morph target and see if it exports right. Or
B: turn on "switch MT" in the options and see it that works.

If those don't work, similar to what Ruz suggested: is the point count the same when you switch between apps? Are you modifying the topology in max at all (adding modifiers and collapsing)?
I've noticed in some rare occasions even if i don't do anything to a mesh in max and re-import that into zbrush, the point count will still change (Probably from having dirty topology to begin with)

Phena

Thanks a lot for your answers! Tried to delite MT and turn on "switch", bake on 2 and 3 subdivs, deleted lower subdives and reconstracted from the higher-and unfortunately haven’t succeed. Same count, no modifiers-just moved few vertices a little to the side. What confuses me is that meshes let to generate displacement. It means that everything is ok with vertex order, isn’t it? And normal maps in Normal map menu are also exported correctly but not in Multi Map exporter.

Phena

Well, after hours of suffering, it turned out that everything works out if you split such problem mesh on polygroups corresponding to UDIMs and bake them separetly.  Wierd and time consuming. Left this note just in case anyone run into this issue again. 

pxgeek

Hmm...that's strange.
I was going to suggest to just try the multi map exporter on your original sculpt (without editing the mesh externally) just as a test to see if that works correctly, and if so, then you'll know it's some kind of issue with transferring the mesh back and forth between apps.

Doubly strange regarding your workaround (I'm assuming you mean splitting your mesh into separate subtools) since I'm able to bake a mesh with multiple udims in one go without issue. (which leads me to believe that your UVs could also be an issue)

At any rate, at least you got your maps exported out

Phena

The truth is out there somewhere. I guess you are right about transfering issue. Probably something went wrong-the project contains a lot of subtools exported from the same Max scene, and this problem appeared only with some of them (including original version). Others baked fine even in cases when mesh had UVs on different UDIMs, like it has to be. 
Anyway, thanks for the help! 

Ruz

Its odd that since I switched to Blender  from max I have had none of these import/export problems
I still use obj exporter and have never had a problem with re importing changes from Blender. (maya was fine for me  too)

max's obj exporter always seemed a bit wonky to me anyway and at some point zbrush started throwing errors if the reimport

was slightly different scale wise maybe 1.02 rather than 1 .

I used to do a trick in max where I added an edit poly, then collapsed back to Editable poly, which seems to work sometimes

Phena

Yeah, scale in Zbrush is a pain. I like Maya, it's the most stable software I experienced. Changed it to Max only because of material system, for me it is more convenient. Didn't get around to Blender yet, its next in line. Often hear about advantages.