Basically, when in transpose mode, you can Ctrl-drag along the your object not too close, eitherand drag a across the surface, following the object. Hold down the Ctrl key, On the left, a Painted can be used to generate masks automatically, affect properties of.
You can see the results below. Mask By Hue derives a mask from the colors in an applied texture, or if no texture is on the model, polypaint will be used. Paint Masks You can paint masks on your object directly by holding down the Ctl key while painting on the model. By default, masked areas show up as dark patches on the model. The Cavity Profile curve controls how the cavities on the mesh are masked.