1. A method, comprising: performing, by a computer: modeling a brush tool representing an erodible media as a height map; collecting information about a user manipulation of a stylus representing a stroke made on a virtual canvas with the brush tool; determining a mark to be made on the virtual canvas dependent on the brush tool model and the collected information; rendering the determined mark; determining a change in the height map of the brush tool due to the stroke dependent on the brush tool model and the collected information; and rendering one or more subsequent marks in response to manipulation of the brush tool dependent on the determined change in the height map.