ZBrushCentral

Brush masking acts odd with Backface Mask on

ZBrush Usage Questions
#1

With backface auto mask on, I can brush mask like normal and the masking doesn’t reach the other side. Basically the backface option doing it’s job. But the moment I do ALT CONTROL to unmask areas, nothing happens. But something is happening, to the other side that is.

I found this out when I was masking the bottom front of some lips, but the brush masked area on the other side of the lip. I didn’t want to redo the mask, so I rotated the model around to unmask the area I didn’t mean to.

I turn on the backface auto mask so this new unmasking doesn’t reach the other side that I want to keep. So I brush with control alt to find it does nothing, the masking is still there.

But it actually did something. When I turned the model back around to the I see it was actually unmasking the area I wanted to keep.

So how do you unmask facing polygons with Backface Auto Masking on without it ignoring them and trying to unmask the other side that’s not suppose to be touched in the first place?

#2

Backface Masking in the Brush palette is separate from polygon masking. The effect you are seeing is due to the Alt behaviour of all brushes - whereby the effect is reversed. So when you hold down the Alt key when the BackfaceMask button is on, the front face becomes masked and the back face unmasked.

If you are painting a mask using Ctrl+drag and wish to unmask some areas without affecting the backfaces, set the BackMaskInt slider to -100. Be sure to switch the slider back to +100 when you’ve done.

Note that for areas that are difficult to sculpt, using polygroups and partial mesh visibility can be a good way of working. You can mask the area you wish to convert to a group, press Tool:Masking:HidePt and then Tool:Polygroups:Group Visible to create a group. See here for more information:

http://www.zbrush.info/docs/index.php/Polygroups

#3

Thanks, I didn’t think to try reverse the back face mask with a negative number. A simple enough work around. I’ll try it next time.

But yes, I have polygroups. Before I imported the new UVs, I used UVmapper to put them into groups, that way I could get polygroups from them.

#4

Of course, you could simply turn backface masking off before you subtract from your mask. This would still only affect the front of the mesh because the back surface is already unmasked. Who cares if your brush carries all the way through the mesh, since you can’t unmask an unmasked area. :wink:

#5

Thanks, I thought about that too, just turning it off when alt-masking since there was no mask on the other side, so it didn’t matter if unmasking reached there :slight_smile: Then just turn backface on again for regular masking. Unless you had different masking behind there that it could reach.

#6

One last thing mask related,

Is there any way to make a stencil restrict the area you can mask? So you can transfer the stencil as a polygon based mask? Right now, Stencils restrict the ZADD and RGB with brushes, but when you mask, the masking goes anywhere regardless of the stencil, which is what some people might want. But is there anyway to fill the stencil with a mask so you can then change the angle? And a way without messing up polypaint if you consider filling the object with black, then paint with white through the stencil and mask based on that like an alpha.

I only thought of this while testing stencil stuff with ZappLink.

#7

You would need to use Projection Master or PolyPainting to paint black and white where you want the masking to be/not be. Then you can derive your mask from the colors of the texture/polypaint.

#8

Hmm, well I guess both those methods would cause you to hurt your polypaint.

I guess I could clone the object I’m painting, then do the black and white thing on that, derive a mask based on those values, then transfer the mask to UVs to reapply to the tool with good polypaint.

But a lot of times you might have removed the uvs to paint with texture in polypaint. Unless one does quick GUV tiles just before cloning it for making the mask, then once you have the mask applied to the original object, disable UVs to continue polypainting. But, then you might never be able to apply that mask again after removing the UVs, unless GUV has a pattern and does it the same way a second time.

Man, there are so many moments in Zbrush where you try to do a work around and just when you think you got it worked out, there’s a but in there.

There’s no way to paint layers is there?

EDIT: After deleting the GUV tiles, then redoing them, the alpha made based of the first GUV worked with the GUV, so it did it the same way the second time.