The Particle Lookat Group node gives artists the ability to easily create a shader that makes a 3D plane 'lookat' the camera.

This is very useful for particle systems that run (partially) on the GPU, but also for things such as trees, grass and other types of billboards that are meant to always face the camera.

Variables such as 'World Up' and 'Particle Size' are exposed for the user in the schematic view for maximum flexibility.