Imposters

Billboards or point sprites are quite often used as "imposters" pretending to be a 3D geometry by showing a 2D image that is always facing the camera. Candera supports both, Billboards and Point Sprites to achieve three-dimensional impressions by showing camera aligned two-dimensional images. 
 In order to relief distinction between Billboards and Point Sprites see following comparison: 
 
 
 
 
 Billboards support rectangular dimension and non-uniform scale. 
 Billboards support different rotation techniques (see Alignment), whereas Point Sprites are always screen aligned. 
 Point Sprites have a performance advantage due to less geometry (one instead of 4 vertices). 
 
 
 
 
 Overall recommendation: Use Point Sprites for spherical shapes like particles, lens flares, sparkles, dust which are screen aligned. \ Further, use Billboards for world up oriented clouds, text, or yaw axis aligned trees, and signs, etc.