I love World Creator, especially the vegetation distribution pipeline. You can create some very realistic fields with it. Im going to check out impostors too - ive seen it a few times and wondered what it's about.
Stupid Rental. My Zbrush that I haven't paid for an update in years and is perpetual Trumps that on all counts.
Effective TDs has presented Storm, a standalone granular simulation tool by Sebastian Schäfer that features the ability to import and export to all major DCC tools. The new system can import geometry in .obj, .SD, or .abc formats for deforming emitters and defectors. What is more, you can export simulations to .prt, .bin. or .abc formats, so the thing is compatible with a wide range of tools.
The app brings a fully multithreaded architecture and an accelerated viewport display to preview millions of particles in real-time.
Controls give users the ability to manage stiffness, constraint forces and more to generate materials. Effective TDs plans to turn Storm into a full multisolver system.