I released version 2.1.2 of Flint today. This version features a number of small changes and two new renderers. The new renderers draw particles as lines rather than discrete images. Each particle is rendered by drawing a line from its previous location to its current location, which enables the creation of effects like hair and grass. You can read about all the changes on the Flint website.
Also on the site and in the downloads is a new example using the new renderers to create grass. The result looks like this.
The grass will look different every time. I have deliberately made this draw slowly so the effect can be seen. It could be rendered much more rapidly by adjusting the parameters. The grass could also be draw instantaneously as a static image by using the runAhead method of the emitter to jump straight to the end state of the system.