Spikes in zBrush model when switching between subdiv levels

GarageBay9

I've been having issues recently with my sculpts, where some of the vertexes get corrupted and turn into long, thin spikes sticking out of the model. Usually it happens when switching back and forth between subdiv levels.

I tried googling the problem and got some hits over on the pixologic forum, but as is kind of par for the course over there, the people who'd asked this question got a jackass attitude non-reply from one of the super-mods. The usual "this question has been asked before, here's a link to a 35 page thread with dozens of different topics in it, you should be happy I even gave you this." And if you dig through that thread, yes, somebody also asked in that thread, but the question never got answered. :poly127:

So I thought I'd ask over here, in a place filled with nice and helpful people.

FWIW, I'm using 3.1 and my workflow usually starts with an all-quad basemesh exported from Max.

Disco Stu

I had this with one obj too.
Maybe undeleted points flying around or scaling issues?
Never got to solve it.

GarageBay9

I usually run an STL check on geometry before I export to zbrush, and fix anything that pops up. I've had this happen with what I'm 100% were clean meshes, so I don't think it was unwelded stuff.

Scaling, I couldn't tell you. I can keep stuff more or less scaled cleanly in max, but I don't know anything about how zbrush scales anything. zbrush is 90% mystery to me still.

vargatom

You're pretty much f***ed, you can try fixing it with the smooth/flatten brushes. We've never been able to find a reason for this bug... only solution is to save often.

Neavah

I've had this problem several times. For me it's usually one of three issues:
a. I've accidentally cloned one or more vertices, and its floating around inside my model (STL will NOT pick this up).

b. I have a area with alot of triangles.

c. Zbrush is grumpy and does it because it can ie: a characters face has some points that do this when its attached to the body, however when separated, its fine.

For me I usually find the area thats got problems - go into max and check it out - cut up the mesh to isolate the area, put it back in zbrush see if it still does it, look for all of the above - then delete and redo what area(s) are wierding out zbrush.
Sometimes I find it best to create the uvs before going into zbrush because missing a floating vert, or a ngon is REEAAALY easy when all our doing is looking through a model - but you'll find it when you create the uvs. then add an xform and turn to poly and 'keep polygons convex' (I do the turn to poly out of habit from past experiences. whether or not it actually helps in all cases I couldn't tell you. My mentalist is 'it can't hurt').

Hope it helps? Good luck!