Lots of improvements such as the new Ripple solver and Rigid Body Cone Twist handles enhance the quality-of-life for FX artists.
Rigid Body Dynamics
Enhancements to the Rigid Body tools include a new Cone Twist interface and support for Curved Glass with Material Fracturing. In addition, occlusion for wind forces is now supported.
From a solver that handles bubble interactions and a ripple solver that can make puddles or simulate a sonic blast hitting a character, Houdini 20 offers practical solutions for VFX artists.
Houdini 20 includes an updated Loop tool as part of SideFX Labs which is ideal for preparing effects for realtime. There is also better access to Open CL for more technical solutions.