Unity Script Reference:
Legacy Documentation: Version 4.3.0
ParticleSystemRenderMode
Description

The rendering mode for particle systems (Shuriken).

This is used by the ParticleSystemRenderer to determine how to render the particles.
Variables
Billboard Render particles as billboards facing the player. (Default)
Stretch Stretch particles in the direction of motion.
HorizontalBillboard Render particles as billboards always facing up along the y-Axis.
VerticalBillboard Render particles as billboards always facing the player, but not pitching along the x-Axis.
Mesh Render particles as meshes.