ZBrushCentral

Question about bump map streaks

ZBrush Usage Questions
#1

Hi, everyone:

I’ve learned ZB for a week and like it deeply. When I found the “bumpviewer” material last week and tried it using different brushes, alpha and strokes, I found a very wierd thing in PM, that is, the bump areas show terraced effects and the level lines are very clear. After I picked it up it still seem the same way. I attach a screenshot for clarifying my idea.bumpStreaks_PM.jpg

I’m not sure if this is caused by AA or alpha image resolution(I tried a 800X800 custom-made image as alpha, still the same result). Because I’m working on a character project and my computer can’t let me subD my model too high, the bump can be a very useful way to make fine details done without any delay in performance. Anyone who can solve this problem please help me. I’m very appreciated for any further help you guys can give.:slight_smile:

#2

Plus the texture resolution is the highest(4096X4096)

#3

Looks like noise from your alpha. But am not 100% sure.

Look at your alpha in photoshop or other program with your alpha on top layer and a white layer underneath. make sure your alpha is the active layer and slowly make it less visible …you will be able to see if those lines are coming from your alpha.

#4

Yes this looks like noise,…must be the alpha, but it can be noise in the material itself !

jantim

#5

aminuts, jantim, thank you guys for the help and info. I checked the Alpha and material settings in ZB, there’s no noise amount anywhere. Plus, I used ZB’s defaul “Brush 07” as Alpha and if I use it to ZAdd or ZSub, it turns out to be smooth, but once used for bump painting and view using “bumpviewer” material, the streaks appear again.

aminuts, I checked the “Brush 07” image in Photoshop, but once I drag it to a white layer, it says it’s a 16bit greyscale image and can’t move. Also, there’s no layer option for such kind of images. I later changed it to 8bit and put it on top of a white layer, lowered the image opacity and didn’t see any noise pattern on it. Any ideas?

Since the same Alpha image works fine with real deformation but not bump painting, I suppose if there’s any setting problems with the material itself? or the document resolution? or AA setting?..I really appreciate the help you guys can give.

#6

I will try to experiment with it later when I have a chance to play but maybe trying…

upping the blur a bit and turning max on (or off if you have it on) in the alpha menu will yield better results with the bvm.

Something to try. I will check it out soon as I can though.

#7

Thank you, aminuts! I’ll also keep trying and tell you my progress. thanks again!

#8

I have a theory.

When bump maps are applied in ZBrush, they can be applied in 16-bit grayscale, which allows for a smooth transition.

However, the color bump material does not have 16 bits at its disposal.

Because the colorbump material must respect each of the R, G, and B channels separately, its bandwith is less than if 1/3 of the color depth of the bitmap. For exaxample, if the color bitmap were 24 bits, the color bump material could only utilize 8 bits, and therefore only display 256 discreet levels. This could result in the terracing that you are seeing.

#9

OwenDouglas pretty well hit the nail on the head.

ZBrush’s alphas are 16 bit grayscale. But when you’re painting with the Bump Viewer material you’re painting a texture. Textures are 8 bit RGB. This means that there are fewer variations in color between black and white, so you can get banding.

What you need to consider is, how much of that banding is actually going to be visible in your render. In the example you show, it was necessary to zoom in really close in order to be able to see it. REALLY close, and look hard. Also, if the render is going to be an animation, any such banding will probably be impossible to see because the eye can’t focus effectively on details in a moving object.

If you know that the banding is going to be visible, then you’ll need to check and see if your rendering engine supports 16 bit images in the bump channel. If it does, then you can create a displacement map and use it as a bump map instead. Displacement maps are generated at 16 bits and retain that when exported as a TIFF or PSD from the Alpha palette. There is no way to create a 16 bit image in the texture palette.

#10

OwenDouglas, your theory clearly tells everything about my question! Now I have the answer to those bump strwak problem. Thank you very much!

aurick, you answer this question in a practical way. Yeah, why should I bother if they can’t be seen during animation or any rendered images other than extreme close-up shot. Also, to convert a 16-bit dispacement map to bump map is a very good idea. I’ll also try this when working. I’ll show what I’ve made in ZB in near future.

This forum is the most open and helpful one I’ve ever met. So many powerful and creative guys are here for help and explore new techniques. AWESOME!