Working With Your Canvas: Basic Controls

From ZBrush Info

These controls affect many or most aspects of painting (or sculpting too, for that matter). For convenience, they are grouped together above the canvas:

They can also be found in their 'real' homes, the xxx....

And here's what they do:

• A number of buttons control what effects are applied to the canvas when painting. Mrgb means use the selected material and color when painting, Rgb means use color but not material, and M means use material but not color.
• When depth painting is on, Zadd means that light area of an alpha pull pixols towards the viewer, while Zsub means light areas of an alpha push pixols away. (But it's normally more convenient to just just one of these, and hold down the 'xxx' key to invert it's meaning.) Zintensity affects how much pushing or pulling is done with each brush stroke. (A useful tip; for most uses, keep Zintensity small, and use repeated brush strokes to do what you want to do.)
• The Brush chooser, Material chooser, Alpha chooser, Tool (paintbrush) chooser, Stroke chooser can all be found on the area to the left of the canvas. Oh, the Color chooser (foreground and background) can be found there too. These choosers can also be found in individual palettes: xx.