Convex Hull creates a geometry that envelops the entire structure of a visualization or of particular categories inside that visualization.
Required Features and Dimensions
Convex Hull requires at least two numerical features mapped to two of the positional dimensions.
Mapping only to the positional dimensions will create a piece of geometry that surrounds the entire visualization. To visualize multiple distributions, map a categorical feature to the Color dimension. Each category in that feature will have its own piece of geometry.