Side Effects Software has has released Houdini Engine for Unreal Engine 4! The plugin has been in beta since earlier this year and is now available to everyone.
Through the integration you can load and Houdini Digital Assets from inside the Unreal Editor and make on-the-fly customizations.
Houdini’s procedural node-based workflow works hand in hand with UE4 to enable artists and designers to achieve beautiful custom content. It's a great way to extend the procedural funcitonality you already get with Unreal and create tools that can be quickly shared to ensure consistent high-quality results.
Read more at sidefx.com/unreal.