ZBrushCentral

Zbrush displacement export scale problem

ZBrush Usage Questions
#1

Hi,
After some weeks of tweaking, my partner and I finally some good displacement export options to Renderman. See pic below:

We’re using ZB3.1 with MD3, and render with
rps 13.5 / rat 7.0 . Our currently working quick-code is DE-LAEU-EAEAEA-D32. But one problem remains. we couldn’t find an optimal scale option that can be applied to all mesh with all object scale without the need to adjusting alpha scale/gain for every output. We’ve tried to use 16-bit and 32-bit ADF, Auto, and Off.

I know some of the posters here recommended using 32-bit with AD Factor (i.e. DE-LBEK-EAEAEA-D32), but these codes doesn’t work for us. Most of the time the map value is very small, and ADF output produced some high frequecy noise. So in the end we turn the scale Off.
I feel that we must find a uniform scale value before it is being able to be used in our production system.
any help or suggestion is very appreciated.

additional info:
our displacement export steps are:

  1. create displacement maps from Displacement menu with DPRes 3, smoothUV on, adaptive Off.
  2. from Alpha menu, select the output map ->DEOptions->enter the quickcode-> Export current.

We’ve tried directly using ZPlugin -> MD3 , but it seems to be buggy and produces inconsistent results. For example if i use ADF to create one map, then change it to Off to create another map, and switch back to ADF to create another, then the third map output is identical to the second one while it suppposed to be identical with the first. I’m not sure if it is the bug of MD3 or I did something wrong.

Another question:
when the scale is off and using 32 bit float, we hope that the zero displacement value is 0,but when we examined it using external viewer, the “neutral” value is 0.5. Is it true the the exporter behaves this way or we do something wrong with the options?

Attachments

sample1.jpg

#2

The reason that you’re always having to adjust values is because the ZBrush interface cannot use a 32-bit image. So when you create your map using the Displacement menu, you’re getting a 16-bit image in the Alpha palette. NO setting in DE can change that 16-bit image to a 32-bit image. (Yeah, it may output as 32-bits, but it’s no better than a 16-bit image. The data that works the “magic” of the 32-bit format so that you don’t have to make adjustments has been lost.)

To get a true 32-bit map, you HAVE to use MD3. This is because MD3 works together with DE to create the map in memory and export it directly from there without ever displaying it directly in ZBrush’s interface.

Any problems that you might be having with MD3 should be carefully documented and described so that they can be duplicated by our development team and corrected if necessary. But for what you’re trying to do you need to be using it.

#3

Thanks for the reply.
But even if i use MD3 with these settings :
32 bit float
scale off
channel 1 zero
channel 2 positive
channel 3 negative

i still can’t get the right displacement value right. What i want is to be able to output the values that are proportional to the scale of the object, so that i don’t need to adjust it anymore in renderman. Technically this is possible, so can you give me the exact steps to achieve this purpose?

My current steps are:

  1. go to lowest level
  2. ZPlugin->MD3:
    UDIM : 0
    InitialFileIndex : 1001
    MaxMapSize : 2048
    MapSizeAdjust : 0
    DpSubPix : 2
    Border : 8
  3. export options : DE-LAEK-AACADA-D32
  4. Create All

Some other questions:

  1. originally i used displacement menu to create displacement alpha,then export, and i found that turning on Smooth UV yields better results for me, so is this option enabled by default in MD3?
  2. whats the difference betweeen Smooth UV option in displacement menu and SUV option in geometry menu?
  3. if i turned off SUV when subdividing, and then turn it on when i go back to level 1 and export displacement, does it have any effect on the displacement? or i have to turn it on from beginning when subdivide the model?
    Thanks in advance.
#4

Heres what they didn’t tell you in science class.
Values that keep shifting are because the map is calulated using the change from level 1- whatever, and the figure is then used to relate that back to object scale. (object scale in Zbrush whats that?) aka(you holding a ruler to the screen;)

So to regulate this I always use the magical UNIFY button under the deformation pallet. Its the ONLY way to know true scale within Zbrush.
Sure its not 100% exact but its close enough that the 32 bit map then uses the 2.2 and -1.1 alpha offsets

Take your highest level then click UNIFY
then make your maps and see if that helps your calculations
of course your settings are a little differnt than mine since i use the traditional code you posted but it should help control that scale issue your having and allow you to find your own magical numbers that span across many models.

#5

thanks alot cannedmushroms.
With unify button pressed, will the model’s scale become different with original scale? also, in the end i will use pre-zbrushed model to be compared with hires model to create the displacement.So does unify have any effect on this procedure?

edit : i have tested it, and indeed it changes the original scale of the object. so Unify can’t solved my problem.

#6

any solution?
anyway, somewhere i saw someone said that MD2 output results are more consistent than MD3. Is it true?anyone has similar experience?
thx.