ZBrush - Using an alpha additive and subtractive at the same time

gestoryscht

Hi guys,
I have a question about using alphas in ZBrush.

Actually to streamline my personal asset creation I scan a lot of rocks out there to create some nice alphas for sculpting.
Now I want to use them, but suddenly I realized something ... I can use these alphas only in an additive or subtractive way - not both ways.

Take a look on the screenshot ~
Plus and minus is what I can get by default, but these structures not representing the real shape of the scan/ alpha.
The lower part is what I want.



Is there a way of changing this behavior? ZBrush takes the 0 - 0.5 values to subtract the surface and 0.5 - 1 adds volume.

Obscura

I'm not a Zbrush pro but generally speaking of math, this would be done by putting the alpha into -1,1 range. So the alpha texture should be 16 bit and should have negative values.

kittinzaa

Go to Alpha>Modify>MidValue

gestoryscht

Hi guys,
thanks for your help and yes - I can imagine that a -1 to +1 range could help ... but it seems ZBrush isn't able to understand these.
I remapped the alpha in SD and exported it as tga/psd/tiff but it doesn't work. The output is still the same but now shrinked as you can see in the SD screenshot.

On the other hand I tried to modify the mid values and this worked - somehow.

The only problem is, that all blacks are getting some 'bad' values, too.

cryrid

If Alphas aren't cutting it, you could look more into turning it into a VDM Brush instead. Some of those examples (such as the mouth) appear to deform surfaces in both directions. 

Obscura

Try using 16F format and to export a tiff, hdr, or exr. Whichever Zbrush can handle.

gestoryscht

I already tried to use a 16F file, but the resulut above is what I get (with a simple alpha). Maybe I am doing something wrong?
Well, but I think I will give VDM brushes a try. From what I read in the last 4 minutes this is exactly what I want.

Thanks!