The impostor tool creates texture sheets to fake 3D objects in your game engine.  The tool will create full octahedral, 3D, fixed axis and animated impostors.  Below is a short video showing how to setup the tool in Houdini.  There is a separate video for Unity users and another video for setting up octahedral impostors in UE4.

The Impostor tool is part of SideFX Labs

UE4 Content Plugin with example files. Unzip the folder and place it in your UE4 project's Plugins folder. Go to Edit > Plugins and make sure the plugin is enabled. In your content browser at the bottom right click on "View Options" and turn on "Show Plugin Content".

Epic's documentation on setting up Impostor Sprites and Ryan Brucks' Content Plugin for Octahedral Impstors.

Unity Package can be found in the Unity folder of the GitHub download. From your Unity project, right click in your Project View and choose "Import Package > Custom Package"

Houdini File