ZBrushCentral

weird artifacts on the displacement map output... need help, please

ZBrush Usage Questions
#1

Hi.

I’m working on my new short an thought it would be a great opportunity to use ZBrush for the displacement maps.
Unfortunately, it is not working the way I want it to work and I get a weird displacement map with wrong displacements around the forehead.

Here is what I do:

  • TOOLS>IMPORT>DEFAULT.OBJ

Import the .obj and draw it on the canvas
(http://www.timreischmann.com/helpme.rar) <- The .obj I use

  • TOOLS>GEOMETRY>DIVIDE

Divide the mesh up to level 4

  • TOOLS>GEOMETRY>SDiv

put it back to 1

  • TOOLS>DISPLACEMENT>DPSubPix

set it to 2 (yea, maybe too high)

  • TOOLS>DISPLACEMENT>DPRes

set it to 2048x2048

  • TOOLS>DISPLACEMENT>MODE

set it to “on”

  • TOOLS>DISPLACEMENT>Create Displacement

export Displacemnt to ALPHA

  • ALPHA> FLIP V

  • ALPHA>EXPORT

export it to a 16-bit .tiff which looks like this

The Problems arounf the eyes and ears are fine, since the UVs overlap
there and I wasn’t planning on using displacement there.
The Problem is the nice implant next to the the forehead.

I could really use some help here.

I uploaded the obj I’m using for this to my website so anybody who wants to help me is welcome to try.

http://www.timreischmann.com/helpme.rar

Thanks.

#2

You have UV coordinates in multiple UV regions. The insides of the eyes and the inside of the mouth have been mapped to seperate UV regions.

When you import an .obj with UVs spread across multiple UV regions/tiles Zbrush registers it and can make use of them if you calculate a displacement map with the Multi Displacement zplugin. For other operations such as painting a texture map, calculating normal maps or calculating displacement maps the normal way, zbrush only uses 1 UV region/tile (0,0 to 1,1) and will add other UV regions on top of that. That will most likely mean overlapping UVs which will create artifacts or a zbrush error when calculating a normal map.

Instead of using Tool > Displacement > Create DispMap use the Multi Displacement zplugin found in the Zplugin palette. I am not sure of its requirements but if you leave Udim at 0 and press GetMeshInfo you can see if it recognises your UV regions/tiles.

Do some test with the zplugin and if all else fails I am sure Aurick can fill you in on the Multi Displacement zplugin.

#3

Thanks a lot. That sounds logical. I’ll give it a shot and post my results when I’m done.

#4

Alright. It’s working - although I do NOT have a clue why. If I leave the UDim at 0 ZBrush creates 3 maps. 2 of them are crappy 32x32 Px .tifs that don’t do any good, but the third map is exactly what I need - the displacement map for the general mesh.

For my problem is solved, I still think it might be nice, if somebody could explain how the MULTI DISPLACEMENT works and what the sliders do.

Might help other people that don’t solve their problems by accident.

Anyway - Thanks a lot TVeyes

#5

Set the MapSizeAdjust slider to 0 to create equal sized displacement maps for each UV tile.

I believe you should position your UVs along the U axis, from left to right. In other words the first tile at 0,0-1,1 the next at 1,0-2,1 and so on. The zplugin should then be able to calculate the fourth UV tile in your object and also add the proper index to the filename.

I just saw you have overlapping UVs around the ears. That is not going to look good when you apply the displacement map in your render application.