ZBrushCentral

strange displacement exporting, image seems half correct half negative value

ZBrush Usage Questions
#1

i work with friend on a simple head, to teach him the zbrush basic.
but when we build the displacement we find a problem :
a part of forehead is inverted (in displacement only) and naturally if use in a 3d software instead to expand forehead we can see an implosion of this part.
in the image you can see the displ map, and in the yellow circle the forehead section that will be in negative and not like this.

any idea?

Attachments

pixologic.jpg

#2

Your not providing much information to help you with.

Does the head have overlapping geometry at that point??? Use the smooth tool and see.

Are you following the base example in The Practical Guide for reference? Does it work? A baseline needs to be established, but it looks like an issue with the model. :wink:

#3

hi Jason, first thanks for fast answer.

it’s a first time that i see that strange thing, i use zbrush from two years, since, buit i never found this kind of problem

i can tell you that :

  • original shape not have overlapped poly, are very smoothed and have a proportional distribution of polys
  • if i load original shape and i sculpt a shape like that, i not have the problem in displacement exporting, only with this tool.
  • i did many other models, but i never see this strange thing.
  • i tried to smooth that area and reshape that, but in this area seems there are some strange thing that give me negative value on displacement (but only with this tool, if i sculpt from start original mesh the problem is not replicable, if i use this tool, problem is replicable).

my goal is to understand why it did me to avoid to work some days on a model that i cannot export at final stage.

other info :
the workflow is common, mesh did in external application (lightwave) loaded in zbrush, store morph, subdivide 6 times, i go to subdiv 2, and i start to sculpt with :
stencil, alpha in PM, pinch, and inflate tool.
uv was did in zbrush, from original mesh i not have uv.

#4

OK, so you didn’t use Projection Master right? That might be what happened.

In Zbrush, load this buggy tool, get the displacement map, with tool still selected load the good tool (without issues) it should just replace this one, add the displacement map to it and see if the problem is still present.

If it is, then it seems the issue is happening when generating the displacement.

Let me know what happens. May have to get an actual Pixologic Wizard in on this if my guess is wrong. :wink:

#5

ehm, yes i used proiection master (alpha in PM), to build small dectails, and two or three big dectails with primitive applied on surface bi projection masterm, but that dectails are ok.

now, i can tell you that the problem is exactly where i used projection master to add a small dectails like skin pores.

but Projection master did it only on the forehead, not in all part where i use it, for example on lips i not see problems (i did dectails in a other PM session, not in same PM session that cause this problem).

my dubs is : why PM give me a problem on displacement if in a geometry ZBrush show me correct shape?

i thought that zbrush use shape to build displacement, if projection master can cause this kind of problems seems that store internally some kind of super displacement info, applied to dinamic shape, but projection master can currupt this…

#6

I don’t think you can blame the software here. Rules need to be followed and if the issue isn’t happening on other works for you and others, the answer usually is that you made a mistake along the way. We’ve all done it, it’s matter of course. Have you tried starting at your lower res and smoothing that area out and working up to the final level so it is smooth? What about removing it with the morph tool, back to the original state for that area? Then redoing. :wink:

#7

probably my word are not clear, sorry for that. i not want to blame zbrush to that, i like a lot zbrush, i only want to understand why i have this problem to avoid it in future.

my morning test on this tool are :

  • i load tool, delete higher subdiv, resculpt it (with same tool and process of yesterday), export disp, all work fine
  • i load tool go to higher level (7), smooth the part that cause problem, and resculpt the part, problem gone, but i must resculpt this part and i not like it.

i not understand the error, what i did to put some info that cause inverting of forehead area in displacement exporting (but in zbrush the shape is correct).
could you give me a simple example of what can cause that?

#8

How much RAM do you have??? :wink:

#9

Hi Jason,
original tool was did in 500mb notebook, i tried to export displacement on the notebook of my friends (500mb of ram) and on my computer that have 2 gb of ram.

#10

It is very possible the tool was corrupted on the machine with lesser RAM. Then saved. ooops!

Did you save the tool at anytime with parts hidden??? Known problem.

Did you save the tool at anytime, not at the lowest subdivision? Known problem.

Something seems to have been done at the wrong time and saved with your file. Not sure I can be much more help. :wink:

#11

hi Jason
usually i follow that you told, save at lower subdiv and with all part visibile, and effectively i never saw problems like that.

but this is a model did from my friend, during a learning session of zbrush, and i’m not sure of all saving process.

thanks for your help.
Carlo