ZBrushCentral

Help with ZMapper vs default ZBrush normals creator

ZBrush Usage Questions
#1

Hi,

I’m a bit of a novice with ZBrush and ZMapper and would like to know why ZMapper produces normal maps (at least in my experience so far) which have a noticeable curvature in areas which should be flat.

Here is an example of a cylinder (the largest area). In the first image, the ZMapper version, there is an obvious gradient from deeper blue to teal, bottom to top. The gradient is in the Z direction, which physically is a straight edge in both my low and high poly versions and doesn’t have the curve suggested by the image:

The second image is the normal map produced using the default Normal Map exporter, using tangent and Adaptive settings, but not smoothUV. This is the result I was expecting, and the same as it appears in Zbrush 2 or using the NVidia filter in Photoshop.

I get the same results on flat surfaces, like a ‘metal’ sheet or a door, a suggested curve from one side to the other where none exists.

Can someone please explain this problem and let me know if there’s a solution or if I should just use the default mapper?

#2

I’ve been unable to duplicate your results with a cylinder. What are your settings in ZMapper?

One thing that I can think of would be if the end caps on your cylinder are different enough to affect the model’s smoothing. If one cap has more polys than the other, it can smooth differently. This can cause the associated polygons – the walls of the cylinder – to smooth differently at each end. Smoothing involves a contraction, and if one end contracts slightly less than the other you’ll see the results in the normal map.

You might try switching from Raytrace mode to Interpolate. This will be closer to ZBrush’s default normal map calculation.

#3

Using Interpolate didn’t change the results.

Here’s an image of my settings with a polyframe shot to show the geometry of the model. Though the top end has some additonal components such as a screw cap, the main body of the cylinder is identical at both ends. I used creasing at max level where the lips come out at each end to keep those ring edges sharp during subdivision with smoothing.

Here is a link to the saved .ZTL file, if anyone has the patience to download it and try mapping it themselves. Download Cannister model

Is there anything in the 3DS Max export options or the modelling itself that would affect ZMapper in a way that the standard normal mapper would not be?

#4

bump

Has anyone else experienced the same thing, or does anyone understand why it’s happening?

#5

I have experienced this many many times, and I have no clue as how to fix it in Zmapper.

My work around is to create a displacement map from Zbrush then take that into Xnormals or Photoshop (nvidia plugin) and create a normal based off the displacement.

That fixes the normal so it doesn’t think that it is ballooning in the middle. Not the best work around, though, so if anyone does know how to fix this, let us know.