Exporting bump map from ZBrush help!?!?

FAT_CAP

I've posted this on the ZBrush Central forum aswell - but I know some of you guys arewell versed with the ZBRUSH import / Export pipelin aswell - probably more so than alot of people on the ZBRUSH central site.

I have been working on a model that I started in 3DSMAX, imported into ZBRUSH and detailed it up to level 5. I think applied the ZBRUSH AUVtiles feature to the model so that I could go in and paint a bump map of the fine details.

However, when I exported the model back into 3DSMAX and applied the bump material I am getting a very different looking bump-map to what I see in ZBRUSH - with the 3DSMAX map having significantly less details and some strange artifacts.



This image shows the 3DSMAX model and bump on the left and the ZBRUSH model and bump on the right. What am I doing wrong here? Is it something I am doing when saving out the texture in ZBRUSH or something else? To me it looks like there are seams along where the ZBRUSH generated UV tiles are split, but if it looks fine in ZBRUSH it should also look fine in MAX...right?

MoP

Er, I quickly edited your post there - you had your FTP login name and password as part of the URL, that's probably not a good idea... unless that was intentional? You can edit that post to fix it... I just didn't want anyone causing trouble...

FAT_CAP

DOH...yeah that was definately a mistaek there! Thanks MOP...that could have gone very wrong!

Still cant work out why Im getting these artifacts on the exported bump map. I tried taking a UV'd version of the low-poly model-that was gonna get the normal map baked on to it- into ZBRUSH and painting a bump onto that and it exports fine n dandy.

Are the artifacts I have in the picture due to me using the AUVTiles thing in ZBRUSH to auto-generate my UVs for the high-poly piece and because iot has so many seams in the UV map - this is where the errors are occurring? I was under the assumption that I didnt need ot UV the hgih-poly model as ZBRUSH could handle this

FAT_CAP

I am still struggling with this one...

I thought the problem might have been the AUV tiles UV generation in ZBRUSH so I tried a test... creating a new texture using GUVtiles and doing a simple bump map test which you can see below. Again - everything looked fine in ZBRUSH, and when applying this texture in MAX it looks fine in the diffuse channel which you can see on the left, but when I put it in the bump channel the artifacts appear again (in different places this time as I had used GUVtiles to create a new set of UV co-ordinates).



This is very strange that there should be sucha big discerpancy between the way the diffuse and bump channels are rendered with a ZBRUSH exported texture.

If anybody could help out it'd be a GREAT help as I dont want to have to paint the bump map by hand or take in the low-poly model (which is UV'd properly in anticipation of normal-mapping) to ZBRUSH and have ot aint the bump-map on that.

MoP

It seems to me that there are segments of UV being flipped, and making the lighting get inverted.

Try mirroring some UV segments in the W channel (not U or V channel!) to get the normals facing the right direction again.

I think this is the problem, although it's mainly guesswork

FAT_CAP

Hmmm - yeah that sounds like it could be it... not sure how that could have happened and its strange that its not showing up in the diffuse channel aswell though. This is the same answer that I got from the moderator on the Pixologic ZBRUSH forums...but they didnt have an answer either

It must be something to do with the way I exported either the model or the map back into MAX from ZBRUSH then. Im not sure how to flip a UV element in the W axis either! Im thinking that as a last resort I could bake the diffuse map onto the low-poly model as that has correct, user-friendly UV-mapping applied..but thats far from ideal.

Any help on this would be much appreciated... as would any help with the correct setting sfor exporting a model and texture with correct texure co-ordinates back into MAX.

FAT_CAP

...or of course I could export the lowest level subdivision and remap it myself, import it again and re-paint the bump map... sounds like alot of work though and there must be a simpler way to get everything exported correctly musn't there?

Entity

have you tried the fix seams option in zbrush before exporting the map? Usually does the trick when I generate normal maps.

EDIT: You can find it under the..texture tab I think. Well its at the same place where you find guvtiles

FAT_CAP

yeah I've tried the fix seams button and it doesnt make any difference unfotuanately... thanks for your help though

Im wondering if this could have been because of mirroring the geometry before taking it into ZBRUSH although the actual geometry is fine and its only the bump which shows the errors.

I've found this thread http://206.145.80.239/zbc/showthread.php?t=28941 over at the forums which Im gonna have a look at during lunchtime...it seems to deal with exporting bump mpas back into MAX so fingers crossed on this one!

Entity

ok then, good luck :P

FAT_CAP

Hmmm - well I've gotten it working by applying the bump map to thte diffuse channel in high-poly model's material, then rendering both the normal map AND the diffuse channel to the low-poly... then switching the baked diffuse to the bump channel. The bump maps in MAX are nowhere near as detailed as the ones I have in ZBRUSH though

Its a bit of an unglorious and un-refined way to go about it all but at least it works for the moment. I'll have to have a bit of a dig around after I have finisehd this character to find out what the problem was with my piepline...hope everything goes well for the rest of the model!

FAT_CAP

Hmm - I think I found the problem. It turns out that the displacement outputted by ZBRUSH also bakes the current bump map into the displacement map it outputs... so when I was exporting the bump from ZBRUSH and applying it again ontop of ht edisplaced map in MAX - something was going wonky and giving me these results.

All seems fine n dandy when I output each map seperately and apply them again in MAX. Just thought I'd add this incase anybody has the same problem in the future.