In XmdvTool brushes can have either a step edge or ramp edge. Step edge brushes allow points to either be completely inside or outside them. When a highlight operation operation is performed on step edge brushes, points that are completely contained by the brush are highlighted, and points not contained are painted in the normal data color.
Ramped brushes do not have a discrete boundary. Instead, along each dimension there is an inner and outer brush boundary. The amount of coverage along one dimension is 1.0 inside the inner boundary and falls linearly to 0.0 at the outer boundary. When a highlight operation is performed on ramped edge brushes, points that are completely contained by the brush are drawn in the normal highlight color for that brush. Points that are partially contained by the brush are drawn in a color that is lighter as the coverage decreases. The amount of ramp of the brush is drawn as a thin line in the same color as the brush coverage on the parallel coordinate and scatterplot displays. On each of these displays, the ramp boundary may be manipulated by holding down the Control key on the keyboard and dragging with the left mouse button.