How do you make watercolor brushstroke to brush on a model with white textured paper? I want the brushstroke to leave some white spots as seen in real watercolor. I hope it is available in ZBrush.
Washington
Here is one suggestion:
Select the solid white square alpha from the Alpha palette
Open the options submenu of the Alpha palette, and increase the alpha’s Noise to maximum, and set the Blur to 0. Maximize Range (Max) should be on and Radial Fade (Rf) should be zero.
Click “Make ST” to create a Stencil out of this alpha. Resize the Stencil to a suitable size.
Paint onto your model’s texture through this stencil
Just a suggestion from someone who hasn’t used ZBrush very long. There probably are better ways to do this. 
Hi Washington
Some tricks
Take the Alpha 23 (with a lot of miniSpheres) and use it with the “drag rect” stroke
so you can make a maxi brush and obtain the wished effect 
You can also use the function “search” of this Post system and type “watercolor” !
I no doubt than you will obtain some helping tricks !
But the better way is creating your own Alpha (with the MrgbzGraber) and use the “Drag Rect” with/or a brush as you are familiar!
It’s very easy 
Hope this help !
Pilou
Ps
I don’t know exactly what effect you wish : send an example
Here a quicky try Zadd On
Image above : Alpha 23, Noise 100, “Drag Rect” stroke maximum on the canvas for enlarge the motif, RGb 100
You can of course play with the Zadd, Zubb, Intensity, colors etc…Explore
And makes many pass from diffrent start!
Have happy Watercoloring
Thank you for the tips… How do you paint on the 3d model?
Washington
To simulate paper texture and leave bits of the surface unpainted, follow Skavens advice. The same technique is used in this thread to simulate charcoal on paper:
You can set the stencil to wrap or conform to the pixols, so the result will look more realistic.
To texture a 3D object, read about Texture Master in the QuickLinks.
There is a program on the market that does an exceptional job of watercolor. It’s called Painter by Corel. I bought an upgrade for it from the painter classic that comes with the Wacom tablet. $150 for the upgrade. Painter is a great program for emulating natural media. It’s watercolor even emulates the pigments floating around in a layer of water until the water is absorbed by the paper, taking the paper texture into account while running the calculations. You can create a watercolor piece in Painter then import the work from Painter into ZBrush.
If you’re just interested in making ZBrush do this set of effects then there is a lot of research that you could get into.
Hi Bholtz
The research in Zbrush can be the challenge
It’s the same pleasure to find a technic than paint with it
Pilou
To paint on the model, use the TextureMaster ZScript. This is the first thumbnail in the second row from the bottom in your default ZScript. Make sure that you have Revision G. If yours is still revision F (it says right on the TextureMaster control panel), you can download the current version from here.
Here is a thread where Stonecutter describes his watercolor technique.
A quick test using Texture Master and the same stencil used in the Sketch script. It looks more like crayon or colored pencil, but it is a start.
The texture that is created is shown in the upper right corner, and it could be taken into Painter for enhancement.
Jaycephus, what setting did you make the canyon?
W
Lots of settings. I used the sketch script that I linked to above. I ran the script, and it set up ZBrush to use a stencil, a certain brush, alpha, etc. I first turned off the Stencil. Then I cleared the layer, selected white, selected a tool, and drew it on the screen. I ran the Texture Master script and pressed Drop. Then I turned the stencil back on, and selected a color such as red. I drew on the object. With the stencil on, the result looks like colored pencil or crayon. When I was done, I pressed Pick in Texture Master. That was it.