I am trying to use displacement maps as alphas to sculpt detail in zbrush. Zbrush seems to limit alpha images to 16 bit, and the downside of this seems to be that there is banding due to the lack of enough info for the smooth gradients. Is there any possible way to be able to import 32 bit alphas to avoid this problem, or any other workaround to solve this issue?
Thanks
You can’t import 32 bit into ZBrush. But I think you are using a map that’s been converted from 8 bit, or degraded in some other way. 16 bit grayscale has over 65,000 levels of gray and doesn’t normally show banding.
Are you using ZBrush rather than ZBrushCore? If so, I’ll move this to the right forum.
Yea sorry, zbrush.
This is bizarre, if I copy the 16 bit version into an 8 bit image, thus downsampling it to 8 bit without dithering, it looks exactly the same with the same banding. If i just downsample the image itself in photoshop, it dithers it to 8bit, which is a particular noisy look. Is there any way to very if zbrush is downsampling my 16bit tif to 8 bit even though it is being imported as an alpha?
This gives me hope at least, because it seems zbrush is working with an 8 bit image, whether zbrush is doing it, or somehow xnormal is only generating an 8 bit image even though the bit depth is 16.
If I mouse over the alpha in zbrush, it says 16 bit for all my alphas, even for the 8 bit image I down sampled to 8bit in photoshop.
For the image properties themselves, the 8 bit image is half of the size of the 16 one.
Thought I found an answer but turned out to be wrong. Still trying to find out why both a 16bit and 8bit displacement map have exactly the same banding artifacts when imported into zbrush as an alpha.
Any chance you can share the alpha? I’d like to take a look.
So we figured out the solution at work today. In order to get true 16bit alphas, you have to import as 16 bit uncompressed grayscale psds. The big trick is that you have to disable automatic photoshop compression and restart photoshop in order to save as an uncompressed psd that zbrush can read.
I couldn’t find any information online that it had to be uncompressed, and there were lots of complaints online about corrupt psds with no solutions, so I don’t know if the zbrush documention/wiki can be updated with this new info, but if possible it will save a lot of headaches.
I was able to convert my 16bit tifs to valid psds once the automatic compression was disabled and it works perfectly now.
When zbrush saves out its own alphas, they are uncompressed, and it was only after comparing the file sizes that we realized why only the zbrush created files worked.
I’ve never heard of this being a problem before. I know ZBrush outputs uncompressed PSDs but I’ve never had any problem with it importing compressed PSDs.
If it’s compressed 16 bit, the alpha just shows up as blank. When you used compressed psds, were they 8 bit or 16?
16 bit, which is what we’re talking about. Anyhow, as I’ve never changed my Photoshop file settings I’d assumed that the 16 bit files were always compressed but that’s not the case.
I’ve looked a little deeper and found that if you save a 16 bit grayscale file which has no layers (just a Background) then it is often uncompressed*, whatever your Photoshop settings. I’m using the latest PS CC but this seems to have been broadly the case for some time:
https://forums.adobe.com/thread/1008471
If I save the file as TIFF format with any sort of compression then I can confirm that ZBrush appears to convert the file to 8 bit (though the pop-up still says 16 bit) with the resulting banding you describe in your first post.
I’ll add some information about this to the online docs.
Nice, thanks for looking into it. Yea i found out maximize compatibility needs to be checked as well on the 16 bit files, otherwise irfanview showed that it still had compression and zbrush couldn’t read it even though photoshop was set to save uncompressed. Confusingly, it was large enough that you’d think it was uncompressed (like 50mb instead of 60mb for a 3 layer file).
So yea, in order to guarantee it will work in zbrush 100% of the time, you need both uncompressed and maximize compatibility. Your info about photoshop choosing to compress or not might explain why I couldn’t get 100% repro during my testing, was confusing as hell.